Diese Arbeit wurde von den National Institutes of Health (DP1CA174426 Carlos F. Barbas) und ShanghaiTech Universität, Shanghai, China (JL) unterstützt. Molekulare Grafiken wurden mit PyMol erzeugt.

1. Klonierung <ol><li> Erhalten Alanin-substituierten Zwei-Finger-ZiF Domänen, die in den pET-28 Expressionsvektorsystem subkloniert haben und sind auf Anfrage erhältlich (pET-2F-ZiF). 34 </li><li> PCR zu amplifizieren EmGFP aus dem Plasmid pBAD-Smaragd mit den Primern 5 &#39;XmaI-EmGFP (5&#39;-GGAAATTG CCCGGG ATGGTGAGCAAGGGCGAGGAGCTGTTCAC-3&#39;; XmaI Website in fett) und 3&#39;-SacI-EmGFP (5&#39;-CGGATCT GAGCTC TTACTTGTACAGCTCGTCCATGCCGAG-3 &#39; ; SacI-Stelle fett gedruckt). <ol><li> Verwenden 5 ng Template-DNA, 10 ul 10x-Polymerasepuffer, 1-Einheiten (U) Taq DNA-Polymerase, 0,2 mM von jedem dNTP und 0,2 &amp; mgr; M von jedem Primer in 100 &amp; mgr; l Lösung mit dem Restvolumen bis destilliertem / deionisiertem Wasser . Verwenden Sie die Zyklusbedingungen: 95 ° C für 5 min; 30 Zyklen von 95 ° C für 30 sec, 55 ° C für 30 sec und 72 ° C für 1 min; 72 ° C für 10 min. Ein Reinigen des PCR-Produkts durch Gel extractiauf und bestimmen, DNA-Konzentration unter Verwendung eines Spektrophotometers Mess Abs 260 x 50 &amp; mgr; g / ml. </li></ol></li><li> Digest pET-2F ZIF und das Insert EmGFP mit den Restriktionsenzymen Xma kodiert I und Sac I in empfohlenen Puffer für 3 h bei 37 ° C unter Verwendung von 10 U Enzym pro 1 ug DNA. Visualisieren DNA durch Agarose-Gelelektrophorese unter Verwendung eines fluoreszierenden interkalierenden Farbstoff wie Ethidiumbromid. </li><li> Reinige den verdauten DNA durch Gelextraktionskit und bestimmen, DNA-Konzentration mit einem Spektrophotometer Mess Abs 260 x 50 &amp; mgr; g / ml. </li><li> Ligation der gereinigten EmGFP kodierenden DNA in 50 bis 100 ng pET-2F-ZiF mit 1 U T4-DNA-Ligase für mindestens 1 h bei RT. Die besten Ergebnisse erzielen, führen Sie die Ligationsreaktion mit einem 6: Einsatz-zu-Vektor-Molverhältnis 1. </li><li> Thaw 50 ul aller chemisch kompetente XL-1 Blue E. coli Zellen auf Eis geben und vorsichtig mischen mit 10-20 ng ligierte pET-2F-ZiF-EmGFP. </li><li> Halten Sie auf Eis für 30 min. Hitzeschock die Mischung bei 42 ° C für 90 sec und erholen sich die Zellen in 2 ml SOB-Medium mit Katabolitrepression (SOC) für 1 Stunde bei 37 ° C unter Schütteln. </li><li> Verbreiten Sie 100 ul der Erholung Kultur auf einem LB-Medium (LB) Agar-Platte mit 50 ug / ml Kanamycin und Inkubation O / N bei 37 ° C. </li><li> Am folgenden Tag inokulieren 6 ml Super Broth (SB) oder LB-Kultur, die 50 ug / ml Kanamycin mit einer Kolonie von der LB-Agar-Platte und Kultur O / N bei 37 ° C. Hinweis: Kolonie-PCR unter Verwendung der Primer 5 &#39;XmaI-EmGFP und 3&#39;-SacI-EmGFP könnte verwendet werden, um positive Klone zu identifizieren, bevor Miniprep werden. </li><li> Reinige pET-2F ZIF-EmGFP durch Miniprep und Plasmid bestätigt durch DNA-Sequenzierung mit T7-Promotors (5&#39;-TAATACGACTCACTATAGGG-3 &#39;). </li></ol> 2. Expression und Reinigung <ol><li> Auftauen 50 ul chemisch kompetente BL21 E. coli-Zellen auf Eis geben und vorsichtig mischen mit 100 ng pET-2F-ZiF-EmGFP plasmid. Transform wie in Schritten von 1,7 bis 1,8 beschrieben. </li><li> Am folgenden Tag impfen 10 ml LB-Medium, das 50 ug / ml Kanamycin mit einer Einzelkolonie und wachsen O / N bei 37 ° C unter Schütteln. </li><li> Am folgenden Tag, verdünnt den 10 ml des O / N-Kultur in 1 l LB-Medium mit 50 ug / ml Kanamycin, 0,2% Glucose und 100 &amp; mgr; M ZnCl 2 ergänzt. Die Kultur bei 37 ° C unter Schütteln bis zu einer optischen Dichte bei 600 nm (OD 600) von 0,8 und induzieren Proteinexpression mit 2 mM Isopropyl-β-D-1-thiogalactopyranosid (IPTG). Nach 6 Stunden Wachstum bei 37 ° C, Ernten der Zellen durch Zentrifugation bei 5.000 × g für 10 min bei 4 ° C. Anmerkung: Induktionsbedingungen sind sehr variabel und hängt von der Stabilität der Proteine ​​exprimiert. Überwachen der OD 600 alle 30 Minuten, bis eine OD 600 von 0,8 erreicht wird. </li><li> Zellpellet in 5 ml Lysepuffer (50 mM Tris-HCl, 500 mM NaCl, 100 &amp; mgr; M ZnCl 2, 1 mM Dithiothreitol (DTT), 1 mM MgCl 2, 1 mM Phenylmethylsulfonylfluorid (PMSF) und 10 mM Imidazol, pH 8,0). Lyse der Zellen auf Eis durch Ultraschallbehandlung mit folgender Einstellung: 50% der Leistung, 4 min Prozesszeit mit 5 s an / 10 sec aus Intervallen. Vermeiden Sie eine Überhitzung der Lösung. </li><li> Zentrifugieren Sie das Zelllysat bei 25.000 · g für 30 min bei 4 ° C und den Überstand in ein frisches Collection Tube. Die besten Ergebnisse erzielen, führen Sie alle folgenden Schritte bei 4 ° C. </li><li> Führen des Überstandes durch eine Säule mit 1 ml äquilibriert Ni-NTA Aufschlämmung vorverpackt. Mit 20 ml Waschpuffer (50 mM Tris-HCl, 500 mM NaCl, 100 &amp; mgr; M ZnCl 2, 1 mM DTT, 1 mM MgCl 2 und 30 mM Imidazol, pH 8,0) Waschen des Harzes. </li><li> Eluieren des Proteins mit 5 ml Elutionspuffer (50 mM Tris-HCl, 500 mM NaCl, 100 &amp; mgr; M ZnCl 2, 1 mM DTT, 1 mM MgCl 2 und 300 mM Imidazol, pH 8,0). </li><li> Buffer tauschen die eluierte Protein mit Speicherpuffer (50 mMTris-HCl, 500 mM NaCl, 100 &amp; mgr; M ZnCl 2, 1 mM DTT, 1 mM MgCl 2 und 10% Glycerin, pH 8,0) und konzentriere das Protein zu mindestens 40 um unter Verwendung einer Spin-Konzentrator durch Zentrifugation gemäß den Anweisungen des Herstellers. </li><li> Bestimmen der Proteinkonzentration von BCA oder Bradford-Test. Mix 2 ul gereinigte Proteine ​​mit 2 &amp; mgr; l 2 × SDS-PAGE-Ladepuffer, Kochen bei 95 ° C für 10 min und dann auf 4% zu lösen -20% Tris-Glycin-SDS-PAGE, um die Proteinreinheit (2) zu bewerten. </li></ol> 3. Protein Lagerung <ol><li> Aliquot des konzentrierten Protein, Flash Einfrieren in flüssigem Stickstoff und bei -80 ° C. Für EmGFP Fusionsproteine ​​umfassen das Röhrchen mit Aluminiumfolie, um das Protein vor Licht zu schützen. </li><li> Vermeiden Sie wiederholtes Einfrieren und Auftauen der Proteinlösung. Hinweis: ZiF-Fusionsproteine ​​sind für mindestens 1 Monat unter diesen Bedingungen stabil. Brachte oder&gt; 4 Monate Lagerung führen kannum Proteinfällung oder Bleichen von EmGFP. </li></ol> 4. Protein Transduction <ol><li> Pflegen HeLa-Zellen in Dulbeccos modifiziertem Eagle-Medium (DMEM), das 10% (v / v) fötalem Rinderserum (FBS) und 1% Antibiotikum-Antimykotikum bei 37 ° C in einer vollständig befeuchteten Atmosphäre mit 5% CO 2. Anmerkung: Die Zellen passagiert mehr als 30 Mal werden für Proteintransduktionsdomäne empfohlen. </li><li> Vorbeschichtung eine Platte mit 24 Vertiefungen mit 500 ul von 50 ug / ml poly-Lysin für 30 bis 60 min bei 25 ° C. Saatgutzellen auf eine Platte mit 24 Vertiefungen in einer Dichte von 2 × 10 5 Zellen pro Vertiefung. Bei 24 Stunden nach dem Aussäen oder einmal Zellen zwischen 80% -90% konfluent, entfernen Medien aus jeder Vertiefung und Waschen mit 500 ul vorgewärmtem serumfreiem DMEM (SFM). </li><li> Zu jeder Vertiefung, fügen Sie 250 ul SFM mit 2 uM ZiF-EmGFP Protein und 100 uM ZnCl 2. Zellen bei 37 ° C für 1 Stunde. Hinweis: ZiF Domains in die Zellen primarily durch Makropinozytose, 34, die eine energieabhängige Mechanismus ist. Daher müssen die Zellen bei 37 ° C für eine effiziente Protein Internalisierung inkubiert werden. </li><li> Entfernen Medien von Zellen, und dreimal mit 500 ul calcium- und magnesiumfreien Dulbeccos phosphatgepufferter Salzlösung (DPBS) mit 0.5 mg / ml Heparin ergänzt. Hinweis: Heparin ist notwendig, um oberflächengebundene Protein, das Downstream-Analysen erschweren könnten, zu entfernen. </li><li> (Optional) Wiederholen Sie die Behandlung bis zu dreimal für erhöhte Auslieferung. </li><li> Isolieren behandelten Zellen unmittelbar nach Heparin Wasch durch Verdau mit 0,05% Trypsin-EDTA bei 37 ° C für 2 min. Resuspendieren abgelösten Zellen in 0,5 ml DPBS mit 1% FBS ergänzt. </li><li> Messen der Fluoreszenzintensität jeder Probe durch Flusszytometrie 35 mit der Fluorescein-Isothiocyanat (FITC) Kanal (Abbildung 3). Stellen Sie die Vorwärtsstreuung (FSC) und Seitwärtsstreuung (SSC), die Bevölkerung zu platzierenInteresse auf der Skala, um sicherzustellen, dass Populationen mit unterschiedlichen Eigenschaften voneinander gelöst. </li><li> Sammle 10.000 Live-Veranstaltungen für jede Probe und die Daten mit Hilfe der Durchflusszytometrie Datenanalyse-Software. 36 Normalisieren Fluoreszenz von HeLa-Zellen mit ZiF-EmGFP auf diese Zellen nur mit SFM behandelten analysieren. </li></ol>

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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+of+Aart,+a+designed+six-finger+zinc+finger+peptide,+bound+to+DNA.">Structure of Aart, a designed six-finger zinc finger peptide, bound to DNA.</a> J. Mol. Biol. 363, 405-421 (2006).</li></ol>

Die Autoren haben nichts zu offenbaren.

Hier wird ein Schritt-für-Schritt-Protokoll für Proteinabgabe mit zellpermeablen Zinkfinger (ZIF) Domänen dargestellt. Das ZiF Domain nicht senken die Aktivität verschmolzen enzymatische Fracht 34; erlaubt die Herstellung und Reinigung von Proteinen in Ausbeuten fast identisch mit denen mit unmodifizierten Protein beobachtet; und kann Proteine ​​und Enzyme mit Wirkungsgraden, die traditionelle zellpenetrierenden Peptid oder Proteintransduktionsdomäne Systeme übersteigen, in einer Vielzahl von Zellty...

Hoch effizient und vielseitig Protein Lieferstrategien sind entscheidend für viele der Grundlagenforschung und therapeutische Anwendungen. Die direkte Lieferung von gereinigten Proteinen in Zellen ist eine der sichersten und einfachsten Methoden, um dies zu erreichen. Im Gegensatz zu 1,2-Strategien, die auf die Genexpression von Nukleinsäuren beruhen, stellt 3-5 Protein Liefer kein Risiko einer Insertionsmutagenese, ist unabhängig von der zelluläre Transkriptions / Translations-Maschinen und ermöglicht eine sofortige Wirkung. Jedoch das Fehlen einfacher und verallgemeinerbar Methoden auszustatten zellpenetrierenden Aktivität an Proteine ​​routine confounds ihrer direkten Eintritt in die Zellen. Aktuelle Verfahren zur Erleichterung der intrazellulären Proteinabgabe auf der Verwendung von natürlich vorkommenden oder 6-8 ausgebildet zellpenetrierenden Peptide 9-12 aufgeladenen Transduktion Domänen 13,14 Nanopartikel 15 und Liposomen, 16 virusähnlichen Partikeln 17,18 basierend </sup&gt; und polymere Mikromaterialien. 19. Leider sind viele dieser Ansätze zeichnen sich durch geringe zelluläre Aufnahme Tarife, 20,21 schlechte Stabilität, 22 unbeabsichtigte Zelltyp-Spezifität, 23 Low endosomalen Flucht Objekte 24 und 25 neben Toxizität. behindert, viele Protein Übertragungstechnologien reduzieren die Bioaktivität der Proteine ​​geliefert. 14 In unserem Labor wurde gezeigt, dass Zinkfinger-Nuclease (ZFN) Proteine ​​- chimären Restriktionsendonukleasen aus einem programmierbaren Cys 2 -His 2 Zinkfinger-DNA-Bindungsprotein und die Spaltdomäne des FokI Restriktionsendonuklease 26-28 - inhärent zell- durchlässig. Es wurde gezeigt, 29 Diese überraschende zellpenetrierenden Aktivität eine intrinsische Eigenschaft des kundenspezifischen Zinkfinger-Domäne, einer DNA-bindenden Plattform, die als ein leistungsfähiges Werkzeug für die gezielte Genom en hervorgegangen sein,Engineering, 30-32 und als das Ergebnis der Konstellation von sechs positiv geladene Reste auf der Proteinoberfläche sein. Tatsächlich haben mehrere DNA-bindenden Proteinen, einschließlich c-Jun und N-DEK wurde gezeigt, dass eine angeborene Fähigkeit, Zellmembranen zu durchqueren besitzen. 33 In jüngerer Zeit haben unser Labor auf diese Ergebnisse und zeigten, dass die Zellen eindringende Aktivität zink- Finger (ZiF) Domains können für den intrazellulären Proteintransport genutzt werden. Genetische Fusion von entweder einem oder zwei Finger ZiF Domänen an spezifische Proteinfracht, ergab einen Wirkungsgrad, die viele herkömmliche zellpenetrierende Peptid Abgabesysteme überschritten Aufnahme. 34 Vor allem ZiF-vermittelte Abgabe nicht beeinträchtigen die Aktivität des fusionierten enzymatische Ladung und erleichtert hohe cytosolische Lieferung. Zusammen zeigen diese Ergebnisse zeigen das Potenzial der ZiF Domäne zur Erleichterung der effizienten und einfachen Verabreichung von Proteinen und möglicherweise mehrere verschiedene Arten von MakroMoleküle, in Zellen. Hier wird eine detaillierte Schritt-für-Schritt-Protokoll zur Implementierung ZiF Technologie für Proteintransport in Säugerzellen präsentiert. Wir zuvor konstruierten eine Reihe von ein-, zwei-, drei-, vier-, fünf- und sechs Finger ZiF Domänen, die die Fähigkeit zur Bindung von DNA, durch Substitution von jeder der α-helicalen DNA-bindenden Reste fehlen, aber fähig sind, liefert Proteine ​​in Zellen 34 (Abbildung 1). Die Herstellung und die Transduktion von Smaragd GFP (EmGFP) in HeLa-Zellen unter Verwendung eines Zwei-Finger-Domäne ZiF beschrieben. Dieses Protokoll ist erweiterbar, um fast jedes Protein in der Lage, lösliche Expression in Escherichia coli und fast jedem Säugerzelltyp. Erwartete Ergebnisse werden bereitgestellt und Strategien für die Maximierung der Leistung des Systems ausgelegt werden ebenfalls diskutiert.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>XmaI</td>
			<td>New England Biolabs</td>
			<td>R0180L</td>
			<td></td>
		</tr>
		<tr>
			<td>SacI</td>
			<td>New England Biolabs</td>
			<td>R0156L</td>
			<td></td>
		</tr>
		<tr>
			<td>Expand High Fidelity PCR system</td>
			<td>Roche</td>
			<td>11759078001</td>
			<td></td>
		</tr>
		<tr>
			<td>dNTPs</td>
			<td>New England Biolabs</td>
			<td>N0446S</td>
			<td></td>
		</tr>
		<tr>
			<td>4-20% Tris-Glycine Mini protein gels, 1.5 mm, 10 wells</td>
			<td>Life Technologies</td>
			<td>EC6028BOX</td>
			<td></td>
		</tr>
		<tr>
			<td>2x Laemmli Sample Buffer</td>
			<td>BioRad</td>
			<td>161-0737</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 DNA Ligase</td>
			<td>Life Technologies</td>
			<td>15224-017</td>
			<td></td>
		</tr>
		<tr>
			<td>BL21 (DE3) Competent E. coli</td>
			<td>New England Biolabs</td>
			<td>C2527I</td>
			<td></td>
		</tr>
		<tr>
			<td>IPTG</td>
			<td>Thermo Scientific</td>
			<td>R0391</td>
			<td></td>
		</tr>
		<tr>
			<td>Zinc Chloride</td>
			<td>Sigma-Aldrich</td>
			<td>208086-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Kanamycin Sulfate</td>
			<td>Fisher Scientific</td>
			<td>BP906-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G8270-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris Base</td>
			<td>Fisher Scientific</td>
			<td>BP152-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Sigma-Aldrich</td>
			<td>S9888-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>DTT</td>
			<td>Fisher Scientific</td>
			<td>PR-V3151&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>PMSF</td>
			<td>Thermo Scientific</td>
			<td>36978</td>
			<td></td>
		</tr>
		<tr>
			<td>Ni-NTA Agarose Resin</td>
			<td>QIAGEN</td>
			<td>30210</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma-Aldrich</td>
			<td>G5516-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Imidazole</td>
			<td>Sigma-Aldrich</td>
			<td>I5513-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>Amicon Ultra-15 Centrifugal Filter Units</td>
			<td>EMO Millipore</td>
			<td>UFC900324</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Life Technologies</td>
			<td>11966-025</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Life Technologies</td>
			<td>10437-028</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic-Antimycotic&#160;</td>
			<td>Life Technologies</td>
			<td>15240-062</td>
			<td></td>
		</tr>
		<tr>
			<td>24-Well Flat Bottom Plate</td>
			<td>Sigma-Aldrich</td>
			<td>CLS3527-100EA</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-Lysine</td>
			<td>Sigma-Aldrich</td>
			<td>P7280</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS, No Calcium, No Magnesium</td>
			<td>Life Technologies</td>
			<td>21600010</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparan Sulfate</td>
			<td>Sigma-Aldrich</td>
			<td>H4777</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>Life Technologies</td>
			<td>25300054</td>
			<td></td>
		</tr>
		<tr>
			<td>Hela cells</td>
			<td>ATCC</td>
			<td>CCL-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Nano Drop ND-1000 spectrophotometer&#160;</td>
			<td>Thermo Fisher Scientific</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>QIAquick PCR Purification Kit</td>
			<td>QIAGEN</td>
			<td>28104</td>
			<td></td>
		</tr>
		<tr>
			<td>QIAquick Gel Extraction Kit</td>
			<td>QIAGEN</td>
			<td>28704</td>
			<td></td>
		</tr>
	</tbody>
</table>

direct protein delivery to mammalian cells using cell-permeable cys2-his2 zinc-finger domains

Due to their modularity and ability to be reprogrammed to recognize a wide range of DNA sequences, Cys2-His2 zinc-finger DNA-binding domains have emerged as useful tools for targeted genome engineering. Like many other DNA-binding proteins, zinc-fingers also possess the innate ability to cross cell membranes. We recently demonstrated that this intrinsic cell-permeability could be leveraged for intracellular protein delivery. Genetic fusion of zinc-finger motifs leads to efficient transport of protein and enzyme cargo into a broad range of mammalian cell types. Unlike other protein transduction technologies, delivery via zinc-finger domains does not inhibit enzyme activity and leads to high levels of cytosolic delivery. Here a detailed step-by-step protocol is presented for the implementation of zinc-finger technology for protein delivery into mammalian cells. Key steps for achieving high levels of intracellular zinc-finger-mediated delivery are highlighted and strategies for maximizing the performance of this system are discussed.

Zwei-Finger-ZiF-EmGFP Fusionsproteine ​​in E. ausgedrückt werden coli mit&gt; 95% Homogenität und hoher Ausbeute (&gt; 25 mg / ml) (Abbildung 2). Im allgemeinen Ein- und Zwei-Finger kann in Mengen nahezu identisch mit denen des Wildtyp-unmodifizierte Protein ZiF Fusionsproteine ​​hergestellt werden. Jedoch in einigen Kontexten sind fünf- und sechs Finger ZiF Fusionsproteine ​​nicht in Ausbeuten hoch genug für nachfolgende Anwendungen hergestellt werden. <p class="jo...

Watch this Scientific Journal Video about Direct Protein Delivery to Mammalian Cells Using Cell-permeable Cys2-His2 Zinc-finger Domains at JoVE.com

Direct Protein Delivery to Mammalian Cells Using Cell-permeable Cys2-His2 Zinc-finger Domains

Zinkfingerdomänen sind eigen zellpermeablen und fähig zur Vermittlung Proteinabgabe in einem weiten Bereich von Säugetierzelltypen. Hier wird eine detaillierte Schritt-für-Schritt-Protokoll zur Durchführung Zinkfinger-Technologie für die intrazelluläre Proteinabgabe dargestellt.

Direkter Protein Lieferung Säugerzellen mit Zellpermeable Cys<sub&gt; 2</sub&gt; -His<sub&gt; 2</sub&gt; Zink-Finger-Domains

Due to their modularity and ability to be reprogrammed to recognize a wide range of DNA sequences, Cys2-His2 zinc-finger DNA-binding domains have emerged ...

direct-protein-delivery-to-mammalian-cells-using-cell-permeable-cys2

Research

JoVE Journal

Biology

Direct Protein Delivery to Mammalian Cells Using Cell-permeable Cys2-His2 Zinc-finger Domains

9.9K Aufrufe.  The Scripps Research Institute.  Zinkfingerdomänen sind eigen zellpermeablen und fähig zur Vermittlung Proteinabgabe in einem weiten Bereich von Säugetierzelltypen. Hier wird eine detaillierte Schritt-für-Schritt-Protokoll zur Durchführung Zinkfinger-Technologie für die intrazelluläre Proteinabgabe dargestellt. 

Serie: Direct Protein Delivery to Mammalian Cells Using Cell-permeable Cys2-His2 Zinc-finger Domains

Long-term Imaging Mammalian Cells using Wide-Field Microscopy

Actually what I'm gonna do, mount it in here first and then swap out You. So now I'm gonna aspirate try and be as gentle as possible.Okay. A few seconds just holding.Okay.Alright.So the important features of our lifestyle imaging grid are that, so it's an inverted scope, which means the objective, the samples here in the objective is underneath. So the objective is pointing up and the whole scope, or practically the whole, practically the whole scope, including the objectives and the sample are at 37 degrees. So everything in this plastic box is at 37 degrees.And right on top of the stage we have an air and CO2 mix. That is 5%CO2. So the idea is that the sample is actually in a cell, it's like a cell incubator.And so we have, this is our mixer for the air and the CO2 and, and it gets humidified and heated and then piped onto the, the sample on the stage.Okay. And today we're just gonna be doing fluorescence one channel GFP fluorescence. This is the hose that the CO2 and 5%CO2 goes in and it just fits into the stage holder.That's important. And then we can close these, take these down, and then we go to our first position. And what I'm gonna do is go to the first field, which is my control sample, and I'll pick positions based on what I see on the screen.So I just make sure I actually look into the microscope in each new, well, because the focal plane for each of the wells is different, the, the dish is not perfectly flat on the bottom. So you will need to make fine adjustments when you move from well to the well. So right now I'm on the first, well, what I'll do is I'll focus, so I just hit, I just told, I just turned on the light, the transmitted light for the microscope.And I have make sure all the light is going to the eye pieces. And so I just look in, make sure I get a nice clean field. And then what I'll do is turn that light off, turn the fluorescence light on, make sure the cells that I'm looking at look healthy and they're not apoptotic.And, and I turn that off. And what I do next is send, so now I'm gonna start picking positions, which means I have to te send the light path to the camera. This is the camera right here.So I tell the microscope to send all the camera, they don't see anything in the eye pieces. What I'll do is in the software controlling the microscope, I'll choose the right filter set, which for our purposes is psy. And then set an exposure time.And I know these cells very well and I know that they take a 0.2 second exposure time. So I tell, that's what I tell the software to do. And what I'll do is hit focus.This is, and it's basically just alive. The, A light will turn on and you can, oh, I don't know if you can see cells, but the reason this is a good field is because there's, all the cells are, even in terms of their fluorescence, There are no apoptotic cells. Apoptotic cells tend to be very bright and there's no dirt or schmutz in the field.And you can see that they're actually, this is a metaphase cell and that's a metaphase cell, that's a cell that's probably just exited mitosis. And I can just tell that because it looks like those are, those two sets of chromatin are very nicely oriented to each other. Like they just exited an face.So that's a good field. So, and now that I know that the exposure time and the filter set is correct, and this is gonna be software specific, I'll go and I'll take positions and now the software has memorized the X, Y, Z position of that field. And then when I do pick another field, it's, and I'll, so when I'm picking, when I'm picking new fields, but in the same, well, I'll use the, I'll move the i'll, I'll turn the shutter, I'll open the shutter and I'll look to see what I see on the screen and I'll pick fields based on that versus looking in the field.So I don't see any of my tonics in there. But again, even nicely centered, these cells will go through my PS I continue, here's a good example. Here's a good example of what I would avoid that, see how bright that is?That's very bright. That's probably remnants of an apoptotic cell. And the reason I would avoid that is because since it's so bright, when the software auto focuses, it will autofocus just on that and it won't be in the same plane as all these other cells.And so I won't get any information from that field. That looks nice. There's a, this is a pro metaphase right here, That's A metaphase.So, and I'm gonna take three positions per well. So that was three positions and now I'm going to go to my next Well, so you can, so what I will probably do is take images every 10 minutes. So it's a compromise.Lifestyle imaging is always a compromise, right? You have to image, you have to keep the cells healthy, especially if you're interested in mitosis. So you have to minimize their exposure to the fluorescent line.And, but you wanna get information. So you have to take images, you have to, so you have to compromise, you have to make a choice about what you want to capture, what kind of information you wanna capture. For our purposes, mitosis tends to take about an hour.So if we're taking 10 minute intervals, that's pretty good. We see prophase, we see metaphase, we see anaphase, and we can, we can see when there are, there are treatments or drugs or siRNAs that affect those specific cell cycle stages. So for our purposes, that's enough, but we always want more.We always want more positions or finer time and interval or something like that. So it's a compromise. So, and then I'll hit start.And so our software, it does an autofocusing pass on the first pass. So once I hit start, it should start auto autofocusing and you'll see the shutter open, open and close between auto focusing. So I'll hit start.So that's the shutter opening and closing. The Z motor is engaging and it's actually trying to find the plane with the most contrast, which will be the most in focus. You can actually see on the screen going in and out of finding the best plane of focus that might be worrisome.So what it does is it, it drives the Z motor to find the best, the most in focus plane focus, well the most in image. And then it acquires picture there and then it learns that Z position. And then we'll use that Z position for the next 12 passes.And then we'll do the auto focusing pass again. What Kind of experiments do they do? Okay, so our lab is mostly interested in understanding what regulates mitic progression, or at least I'm most interested in understanding that.So with live cell imaging and especially our multi position, long-term imaging scope, you can take, you can film cells for two or three days entering anding mitosis, and you can image multiple rounds of mitosis so you can understand. And then you can put drugs or RNAs or any kind of perturbations on the cells that you would like to study. So you can understand how, how those drugs or, or genes are, are important in regulating mitotic progression.Because it's not fixed cell work and live cell work, you can understand what, when you need to have a perturbation to affect mitosis or what stage of mitosis is affected. So it's really powerful in that respect. What, what are the main technical elements of this experiments?What are the possible problems? Well, the biggest problem besides getting the rig set up, getting the rig set up is not trivial. A lot of people have the rig, but just making sure it works well for your application.The financial element is not, you know, is not small. So there's the setting up of the apparatus and then, and then once you gather the data, there's a real data analysis issue. It takes these movie, if, so, if you're gathering 40 movies each with 30 cells, so you have 40 in 40 fields that you just filmed and each of those fields has 30 cells, then you have to sit down with each one of those movies and look at each one of those cells in that movie.So it takes a really long time to do data analysis. And that's, so it takes a week to analyze data that it took you two days to collect. So there's a, that's a very big obstacle in terms of gathering lots of data.So it's not, while it's high throughput data collection, it's not high throughput analysis. So what would you make to make this experiment really high throughput? So our lab is in the process of developing a program that does the data analysis automatically.And it's a pretty decent program. It's not perfect. The human eye is always better, but it's getting there.So What are the interesting application of this experiment? Maybe other fields you can mention? Besides cell division?You mean for the, oh, for the live cell imaging? Yes.Well, you can do cell motility assays. You can, depending on the, the microscopy that's involved, you can, you know, look at how cells, you could look at tumor development if you really wanted to.But there, you, you're, if as long as you have the right imaging set up, you can, you're pretty much not limited in terms of anything. Our scope happens to be just a wide field and we use 20 by 20 x objective. So it's a pretty low resolution set up, but that's sufficient for what we need to see.So there are, but there definitely aren't, you wouldn't be limited. Anything that has any dynamic kind of experiment, which is biology, it would be, would really benefit from lifestyle imaging. So calcium imaging, although you couldn't do it on our apparatus, that's a live cell.You definitely need live cell imaging for that. Like I said, patient assays, motility assays, those kinds of things would really benefit from live cell imaging. Would you like to tell a few words about your previous experience?How long do you work on these techniques? What do you you work on before? Wow.So in my PhD I didn't work.I did a lot of confocal microscopy, but no lifestyle imaging. And so during my postdoc I was, I helped Dr.King get this apparatus that, that we just used to set up these fragment, get that up and running. And, and so during my postdoc, I had a lot of experience with both widefield with TimeLapse imaging on our scope, which is the widefield and also TimeLapse imaging with confocal microscopy.And I would say that it's really powerful. You get a lot of information, but it's not easy to get working perfectly. So it really requires a lot of attention and a lot of attention to details at every little step of the process.And, and then you still have problems. So it's a tough application, but you can really get, if, if it's what you need to have to, to study your problem, your scientific problem, then it, it's invaluable in that respect, but it's tough. So find someone who knows what they're doing and use them.That's my advice. So good.

Langfristige Imaging Säugetierzellen mit Wide-Field-Mikroskopie

Forschung

Biologie

Trypsinizing and Subculturing Mammalian Cells

As cells reach confluency, they must be subcultured or passaged. Failure to subculture confluent cells results in reduced mitotic index and eventually in cell death. The first step in subculturing is to detach cells from the surface of the primary culture vessel by trypsinization or mechanical means. The resultant cell suspension is then subdivided, or reseeded, into fresh cultures. Secondary cultures are checked for growth and fed periodically, and may be subsequently subcultured to produce tertiary cultures. The time between passaging of cells varies with the cell line and depends on the growth rate.

As cells reach confluency, they must be subcultured or passaged. This video will demonstrate a procedure for subculturing both adherent and suspension cells.

Trypsinizing und Subkultivierung Säugerzellen

As cells reach confluency, they must be subcultured or passaged. Failure to subculture confluent cells results in reduced mitotic index and eventually in ...

Engineering Cell-permeable Protein

The protein transduction technique enables the direct delivery of biologically active material into mammalian cells [for review see 1,2]. For this one can make use of the translocating ability of so-called cell penetrating peptides (CPPs), also designated as protein transduction domains (PTDs). The TAT-CPP derived from the human immunodeficiency virus type 1 (HIV-1) Tat (trans-activator of transcription) protein has been widely used. The positively charged TAT promotes cell permeability thereby overcoming the barriers of the cellular membrane by endocytosis or/and direct membrane penetration2. In combination with a nuclear localization signal (NLS) fusion proteins are able to enter the nucleus exhibiting functionality. Our video presentation demonstrates, as an exemplification for the engineering of cell-permeable proteins, the construction, production and application of a cell-permeable version of the DNA-modifying enzyme Cre.
Cre is a site-specific recombinase that is able to recognize and recombine 34 base pair loxP sites in mammalian cells in vitro and in vivo. Therefore the Cre/loxP system is widely used to conditionally induce mutations in the genome of living cells3,4. The delivery of active Cre recombinase to cells, however, represents a limitation.
We describe the pSESAME vector system, which allows a direct insertion of the gene-of-interest and provides a platform to rapidly clone different domains and tags used within the vector in a convenient and standardized manner. Rearranging of the different tags has been shown to modify the biochemical properties of the fusion proteins providing a possibility to achieve higher yield and better solubility. We demonstrate how to express and purify recombinant cell-permeant proteins in and from E. coli. The functionality of the recombinant Cre protein is finally validated in cell culture by assessing its intracellular recombinase activity.

Protein transduction enables the direct delivery of biologically active proteins into cells. In contrast to conventional methods such as DNA transfection or viral transduction this non-invasive paradigm allows highly efficient cellular manipulation in a titratable manner circumventing cellular toxicity and the risk of oncogenic transformation by permanent genetic modification.

Engineering zellpermeablen Protein

The protein transduction technique enables the direct delivery of biologically active material into mammalian cells [for review see 1,2]. For this one can ...

Using the GELFREE 8100 Fractionation System for Molecular Weight-Based Fractionation with Liquid Phase Recovery

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based fractionation. The system is comprised of single-use, 8-sample capacity cartridges and a benchtop GELFREE Fractionation Instrument. During separation, a constant voltage is applied between the anode and cathode reservoirs, and each protein mixture is electrophoretically driven from a loading chamber into a specially designed gel column gel. Proteins are concentrated into a tight band in a stacking gel, and separated based on their respective electrophoretic mobilities in a resolving gel. As proteins elute from the column, they are trapped and concentrated in liquid phase in the collection chamber, free of the gel. The instrument is then paused at specific time intervals, and fractions are collected using a pipette. This process is repeated until all desired fractions have been collected. If fewer than 8 samples are run on a cartridge, any unused chambers can be used in subsequent separations.
This novel technology facilitates the quick and simple separation of up to 8 complex protein mixtures simultaneously, and offers several advantages when compared to previously available fractionation methods. This system is capable of fractionating up to 1mg of total protein per channel, for a total of 8mg per cartridge. Intact proteins over a broad mass range are separated on the basis of molecular weight, retaining important physiochemical properties of the analyte. The liquid phase entrapment provides for high recovery while eliminating the need for band or spot cutting, making the fractionation process highly reproducible1.

The accompanying video describes the use of the GELFREE 8100 Fractionation System, which partitions complex protein samples on the basis of molecular weight and recovers the fractions in liquid phase. The video describes how the technology works, how it is used, and provides resultant data, with polyacrylamide gel electrophoresis analysis of fractionated bovine liver homogenate.

Mit dem GELFREE 8100 Fraktionierung System für Molecular Weight-Based Fraktionierung mit Liquid Phase Wiederherstellung

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based ...

Genome Editing with CompoZr Custom Zinc Finger Nucleases (ZFNs)

Genome editing is a powerful technique that can be used to elucidate gene function and the genetic basis of disease. Traditional gene editing methods such as chemical-based mutagenesis or random integration of DNA sequences confer indiscriminate genetic changes in an overall inefficient manner and require incorporation of undesirable synthetic sequences or use of aberrant culture conditions, potentially confusing biological study. By contrast, transient ZFN expression in a cell can facilitate precise, heritable gene editing in a highly efficient manner without the need for administration of chemicals or integration of synthetic transgenes.
Zinc finger nucleases (ZFNs) are enzymes which bind and cut distinct sequences of double-stranded DNA (dsDNA). A functional CompoZr ZFN unit consists of two individual monomeric proteins that bind a DNA "half-site" of approximately 15-18 nucleotides (see Figure 1). When two ZFN monomers "home" to their adjacent target sites the DNA-cleavage domains dimerize and create a double-strand break (DSB) in the DNA.1 Introduction of ZFN-mediated DSBs in the genome lays a foundation for highly efficient genome editing. Imperfect repair of DSBs in a cell via the non-homologous end-joining (NHEJ) DNA repair pathway can result in small insertions and deletions (indels). Creation of indels within the gene coding sequence of a cell can result in frameshift and subsequent functional knockout of a gene locus at high efficiency.2 While this protocol describes the use of ZFNs to create a gene knockout, integration of transgenes may also be conducted via homology-directed repair at the ZFN cut site.
The CompoZr Custom ZFN Service represents a systematic, comprehensive, and well-characterized approach to targeted gene editing for the scientific community with ZFN technology. Sigma scientists work closely with investigators to 1) perform due diligence analysis including analysis of relevant gene structure, biology, and model system pursuant to the project goals, 2) apply this knowledge to develop a sound targeting strategy, 3) then design, build, and functionally validate ZFNs for activity in a relevant cell line. The investigator receives positive control genomic DNA and primers, and ready-to-use ZFN reagents supplied in both plasmid DNA and in-vitro transcribed mRNA format. These reagents may then be delivered for transient expression in the investigator&#x2019;s cell line or cell type of choice. Samples are then tested for gene editing at the locus of interest by standard molecular biology techniques including PCR amplification, enzymatic digest, and electrophoresis. After positive signal for gene editing is detected in the initial population, cells are single-cell cloned and genotyped for identification of mutant clones/alleles.

Genome Editing with CompoZr Custom Zinc Finger Nucleases ZFNs

The CompoZr Custom Zinc-Finger Nuclease (ZFN) Service enables precise genome editing in any organism or cell line at any locus defined by the user. This article describes the process for the design, manufacture, validation and implementation of the CompoZr Custom ZFN Service.

Genome Editing mit CompoZr Benutzerdefinierte Zinkfinger Nukleasen (ZFNs)

Genome editing is a powerful technique that can be used to elucidate gene function and the genetic basis of disease. Traditional gene editing methods such ...

Investigating Protein-protein Interactions in Live Cells Using Bioluminescence Resonance Energy Transfer

Assays based on Bioluminescence Resonance Energy Transfer (BRET) provide a sensitive and reliable means to monitor protein-protein interactions in live cells. BRET is the non-radiative transfer of energy from a 'donor' luciferase enzyme to an 'acceptor' fluorescent protein. In the most common configuration of this assay, the donor is Renilla reniformis luciferase and the acceptor is Yellow Fluorescent Protein (YFP). Because the efficiency of energy transfer is strongly distance-dependent, observation of the BRET phenomenon requires that the donor and acceptor be in close proximity. To test for an interaction between two proteins of interest in cultured mammalian cells, one protein is expressed as a fusion with luciferase and the second as a fusion with YFP. An interaction between the two proteins of interest may bring the donor and acceptor sufficiently close for energy transfer to occur. Compared to other techniques for investigating protein-protein interactions, the BRET assay is sensitive, requires little hands-on time and few reagents, and is able to detect interactions which are weak, transient, or dependent on the biochemical environment found within a live cell. It is therefore an ideal approach for confirming putative interactions suggested by yeast two-hybrid or mass spectrometry proteomics studies, and in addition it is well-suited for mapping interacting regions, assessing the effect of post-translational modifications on protein-protein interactions, and evaluating the impact of mutations identified in patient DNA.

Interactions between proteins are fundamental to all cellular processes. Using Bioluminescence Resonance Energy Transfer, the interaction between a pair of proteins can be monitored in live cells and in real time. Furthermore, the effects of potentially pathogenic mutations can be assessed.

Untersuchung von Protein-Protein-Interaktionen in lebenden Zellen Mit Biolumineszenz-Resonanz-Energie-Transfer

Assays based on Bioluminescence Resonance Energy Transfer (BRET) provide a sensitive and reliable means to monitor protein-protein interactions in live ...

siRNA Screening to Identify Ubiquitin and Ubiquitin-like System Regulators of Biological Pathways in Cultured Mammalian Cells

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that regulates diverse biological pathways including the hypoxia response, proteostasis, the DNA damage response and transcription.&#160; To better understand how UBLs regulate pathways relevant to human disease, we have compiled a human siRNA &#8220;ubiquitome&#8221; library consisting of 1,186 siRNA duplex pools targeting all known and predicted components of UBL system pathways. This library can be screened against a range of cell lines expressing reporters of diverse biological pathways to determine which UBL components act as positive or negative regulators of the pathway in question.&#160; Here, we describe a protocol utilizing this library to identify ubiquitome-regulators of the HIF1A-mediated cellular response to hypoxia using a transcription-based luciferase reporter.&#160; An initial assay development stage is performed to establish suitable screening parameters of the cell line before performing the screen in three stages: primary, secondary and tertiary/deconvolution screening. &#160;The use of targeted over whole genome siRNA libraries is becoming increasingly popular as it offers the advantage of reporting only on members of the pathway with which the investigators are most interested.&#160; Despite inherent limitations of siRNA screening, in particular false-positives caused by siRNA off-target effects, the identification of genuine novel regulators of the pathways in question outweigh these shortcomings, which can be overcome by performing a series of carefully undertaken control experiments.

Here, we describe a methodology to perform a targeted siRNA &#8220;ubiquitome&#8221; screen to identify novel ubiquitin and ubiquitin-like regulators of the HIF1A-mediated cellular response to hypoxia.&#160; This can be adapted to any biological pathway where a robust read out of reporter activity is available.

siRNA Screening zu Ubiquitin und Ubiquitin-ähnlichen System Regler der biologischen Stoffwechselwege in kultivierten Säugerzellen identifizieren

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that ...

Identification of Protein Interaction Partners in Mammalian Cells Using SILAC-immunoprecipitation Quantitative Proteomics

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants. Low affinity interactions can be preserved through the use of less-stringent buffer conditions and remain readily identifiable. This protocol discusses the labeling of tissue culture cells with stable isotope labeled amino acids, transfection and immunoprecipitation of an affinity tagged protein of interest, followed by the preparation for submission to a mass spectrometry facility. This protocol then discusses how to analyze and interpret the data returned from the mass spectrometer in order to identify cellular partners interacting with a protein of interest. As an example this technique is applied to identify proteins binding to the eukaryotic translation initiation factors: eIF4AI and eIF4AII.

SILAC immunoprecipitation experiments represent a powerful means for discovering novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants, and low affinity interactions preserved through use of less-stringent buffer conditions.

Identifizierung von Protein-Interaktionspartner in Säugetierzellen mit SILAC-Immunpräzipitation Quantitative Proteomics

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel ...

Zinc-finger Nuclease Enhanced Gene Targeting in Human Embryonic Stem Cells

One major limitation with current human embryonic stem cell (ESC) differentiation protocols is the generation of heterogeneous cell populations.&#160;These cultures contain the cells of interest, but are also contaminated with undifferentiated ESCs, non-neural derivatives and other neuronal subtypes.&#160; This limits their use in in vitro and in vivo applications, such as in vitro modeling for drug discovery or cell replacement therapy. To help overcome this, reporter cell lines, which offer a means to visualize, track and isolate cells of interest, can be engineered.&#160;However, to achieve this in human embryonic stem cells via conventional homologous recombination is extremely inefficient.&#160;This protocol describes targeting of the Pituitary homeobox 3 (PITX3) locus in human embryonic stem cells using custom designed zinc-finger nucleases, which introduce site-specific double-strand DNA breaks, together with a PITX3-EGFP-specific DNA donor vector. Following the generation of the PITX3 reporter cell line, it can then be differentiated using published protocols for use in studies such as in vitro Parkinson&#8217;s disease modeling or cell replacement therapy.

Reporter cell lines offer a means to visualize, track and isolate cells of interest from heterogeneous populations.&#160;However, gene-targeting using conventional homologous recombination in human embryonic stem cells is extremely inefficient. Herein, we describe targeting CNS midbrain specific transcription factor PITX3 locus with EGFP using zinc-finger nuclease enhanced homologous recombination.

Zinkfinger-Nuklease Verbesserte Gene Targeting in humanen embryonalen Stammzellen

One major limitation with current human embryonic stem cell (ESC) differentiation protocols is the generation of heterogeneous cell ...

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and the inherent instability of many membrane proteins once solubilized in detergents. A protocol is described that combines ligation independent cloning of membrane proteins as GFP fusions with expression in Escherichia coli detected by GFP fluorescence. This enables the construction and expression screening of multiple membrane protein/variants to identify candidates suitable for further investment of time and effort. The GFP reporter is used in a primary screen of expression by visualizing GFP fluorescence following SDS polyacrylamide gel electrophoresis (SDS-PAGE). Membrane proteins that show both a high expression level with minimum degradation as indicated by the absence of free GFP, are selected for a secondary screen. These constructs are scaled and a total membrane fraction prepared and solubilized in four different detergents. Following ultracentrifugation to remove detergent-insoluble material, lysates are analyzed by fluorescence detection size exclusion chromatography (FSEC). Monitoring the size exclusion profile by GFP fluorescence provides information about the mono-dispersity and integrity of the membrane proteins in different detergents. Protein: detergent combinations that elute with a symmetrical peak with little or no free GFP and minimum aggregation are candidates for subsequent purification. Using the above methodology, the heterologous expression in E. coli of SED (shape, elongation, division, and sporulation) proteins from 47 different species of bacteria was analyzed. These proteins typically have ten transmembrane domains and are essential for cell division. The results show that the production of the SEDs orthologues in E. coli was highly variable with respect to the expression levels and integrity of the GFP fusion proteins. The experiment identified a subset for further investigation.

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

A streamlined approach to screening for the expression of recombinant membrane proteins in Escherichia coli based on fusion to green fluorescent protein is presented.

Green Fluorescent Protein-basierte Screening Expression von Membranproteinen in<em&gt; Escherichia coli</em

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and ...

Direkter Protein Lieferung Säugerzellen mit Zellpermeable Cys

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