Damos las gracias a Anne-Marie Dion-Cote para los debates que conducen al desarrollo del método. JK y RB son FQNRT académicos de doctorado, M.-MG es un erudito Vanier CIHR, y J.-YM es un investigador senior FRSQ. Este trabajo fue apoyado por fondos de las Ciencias Naturales e Ingeniería de Investigación de JY. M.

1. Producción de baculovirus recombinante Los baculovirus son generados utilizando el sistema de expresión de baculovirus Bac-to-Bac de Invitrogen principalmente de acuerdo con el protocolo del fabricante con modificaciones sólo leves: <ol><li> A pFastBac1 vector modificado (Gibco, la vida) fue creado que contiene el GST y Sus etiquetas (Figura 2). El sitio de clonación múltiple (MCS) de un pET-52b (+) vector (Novagen), que contiene una 10xHis-tag, se insertó en el MCS de un vector pFastBac1 generar pFastBac1-Strep-10xHis. La secuencia de MCS pET-52b (+) fue amplificado por PCR entre los sitios de restricción XbaI y BLPI, la adición de un sitio de restricción BglII en el extremo 5 &#39;y un sitio de restricción HindIII en el extremo 3&#39;. El producto de PCR se clonó entonces entre BamHI y el sitio de restricción HindIII de pFastBac1, usando la compatibilidad de las secuencias de restricción BamHI y BglII. Puesto que el objetivo era generar un pFastBac1 permite la expresión deproteína recombinante con estreptavidina y 10xHis-tags, el sitio de restricción BamHI de pET-52b (+) no se utilizó la secuencia de MCS. Además, el sitio de restricción XbaI no se utilizó para evitar la redundancia de los sitios de restricción que se producen entre los sitios que ya están en el MCS de pFastBac1 y estos insertado con el MCS de pET-52b (+). A continuación, se inserta la secuencia de codificación GST con el sitio PreScission proteasa reconocimiento (LeuGluValLeuPheGln / GlyPro) en pFastBac1-Strep-10xHis. La secuencia de ADNc de GST a partir de pGEX-6P-2 (GE Healthcare) se amplificó por PCR con cebadores que contienen sitios de restricción NcoI y KpnI en los extremos 5 &#39;y 3&#39; extremidades, respectivamente. El sitio NcoI permite la adición de un codón de inicio sino también una alanina a la GST. El producto de PCR fue clonado en pFastBac1-Strep-10xHis entre los sitios de restricción NcoI y KpnI, dando lugar a la supresión de la estreptavidina-tag. El nuevo vector de fusión así obtenido se denominó pFastBac1-GST-10xHis. </li><li> Clonar el ADNc que codifica para la prOtein de interés en el vector pFastBac-GST-10xHis entre la GST (N-terminal) y la etiqueta de His (C-terminal). Tenga cuidado de eliminar el codón de parada de ADNc para permitir la fusión con el extremo C-terminal de His-tag. </li><li> Transformar E. coli DH10Bac con el pFastBac recombinante (obtenida en la etapa 1.2) para generar el bácmido. Permitir colonias para crecer durante la noche a 37 ° C y varias horas a 30 ° C en placas de selección que contienen Bluo-gal e IPTG (10 mg / ml de tetraciclina, 50 mg / ml de kanamicina, 7 mg / ml de gentamicina, 100 mg / ml de Bluo- Gal, 40 g / ml de IPTG). </li><li> Pick and restreak 2 colonias blancas (del Paso 1.3) en placas de selección para confirmar el fenotipo blanco. </li><li> Inocular 2 ml de LB que contienen 10 mg / ml de tetraciclina, 50 mg / ml de kanamicina, 10 mg / ml de gentamicina con las dos colonias blancas de la etapa 1.4 y dejarlos crecer durante la noche bajo agitación (250 rpm) a 37 ° C. </li><li> Con el fin de purificar el ADN bácmido, sedimentar las bacterias de la etapa 1.5,resuspender las células en 300 l de solución I y añadir 300 l de solución II (kit de Qiagen maxiprep). Incubar durante 5 min a temperatura ambiente, añadir 300 l de 3 M KOAc pH 5,5 y se incuba durante 10 minutos en hielo. Centrifugar las muestras a 4 º C, la velocidad máxima durante 10 min. Añadir 800 l de isopropanol a los sobrenadantes y se incuba durante 10 minutos en hielo. Centrifugar las muestras durante 15 min a 4 ° C y lavar el precipitado con 500 l de etanol al 70%. Deje que el pellet seco y resuspender en condiciones estériles en 40 l de Tris-EDTA pH 8,0. El ADN bácmido debe almacenarse a 4 ° C. </li><li> Generar baculovirus como se describe en el protocolo del fabricante. Los baculovirus se pueden almacenar a 4 º C protegidas de la luz. </li></ol> 2. Expresión de proteínas recombinantes <ol><li> Con el fin de elegir el baculovirus más eficiente para la purificación y para vigilar a qué hora se alcanza el pico de expresión de la proteína, lleve a cabo un ensayo de mini-infección de unas sigue: Infect 2 x 10 7 Sf9 de células infectadas se cultivaron a 27 ° C en medio de Grace (complementado con 10% de FBS y 1% P / S) con 133 l (1/150) de baculovirus. Recoger alícuotas de 1,5 ml a 0, 24, 48, y 72 horas después de la infección. Sedimentar las células y analizar el nivel de expresión de la proteína de interés mediante transferencia Western usando anticuerpos anti-etiqueta. </li><li> Utilice el baculovirus más eficiente desde el paso 2.1 para infectar una ruleta que contiene 1,0 x 10 6 células Sf9 por ml en 500 ml de los medios de comunicación con una proporción de 1/150 entre el virus y los medios de comunicación. Deje que las células infectadas crecen en suspensión a 27 º C y cosechan las células cuando se alcanza la máxima expresión de proteínas (según lo determinado en el paso 2.1). Las células sedimentadas se pueden almacenar a -80 ° C hasta su uso posterior. </li></ol> 3. Preparación de lisado celular soluble Todas las siguientes etapas de incubación se llevan a cabo a 4 ° C en rotación suave. <ol><li> Lyse Scélulas F9 que expresan su proteína de interés en ~ 20 ml de tampón de unión de GST (NaCl 150 mM, EDTA 1 mM, 0,05% de Triton-X-100, 1 mM de DTT en PBS1X para una concentración final de NaCl de 250 mM, y el inhibidor de la proteasa cóctel (Roche). En un baño de agua helada, Dounce la solución 20x con un homogeneizador Dounce, sonicar 3x 30 segundos cada uno (salida 70%), y de nuevo Dounce 20x. </li><li> (Opcional). Incubar el lisado total de células con 1 mM de MgCl 2 y Benzonase nucleasa 7 (2,5 U / ml) durante 30 min a 4 ° C para eliminar la contaminación de ADN o ARN. </li><li> Centrifugar a 18000 rpm durante 30 min a 4 ° C. Mantenga el sobrenadante. </li><li> (Opcional). Centrifugar el sobrenadante de nuevo durante 30 min a 18.000 rpm a 4 ° C para obtener un lisado soluble clara. Pasar el sobrenadante a través de un filtro de 0,2 o 0,45 micras para evitar obstrucciones. </li></ol> 4. Unión de la proteína en los granos de GST <ol><li> Incubar el lisado soluble de células con 1 ml de perlas de GST (previamente lavada dos veces con10 ml de tampón de unión de GST) durante 1 hora a 4 ° C en rotación suave. </li></ol> Comentario: El tiempo de incubación debe ser optimizado de acuerdo a la estabilidad de la proteína y la eficacia de unión. <ol start="2"><li> Un paseo rápido a 700 rpm y eliminar el sobrenadante que contiene las proteínas no unidas (esto se pueden mantener para su posterior análisis). Lavar las proteínas GST unida (Figura 3B, pista 1) con tampón de lavado de GST (GST tampón de unión con 350 mM de NaCl final de). </li><li> Repita el paso 4.2 2x. En el último lavado, eliminar la mayor cantidad sobrenadante como sea posible. </li><li> Incubar las perlas con 5 mM de ATP y 15 mM de MgCl 2 (en tampón de unión 10 ml de GST) durante 1 hora a 4 ° C para evitar la unión no específica de proteínas de choque térmico 8. Lavar las perlas tres veces con tampón de lavado de GST. </li></ol> 5. PreScission escisión del GST <ol><li> Centrifugar las perlas de GST, separar el sobrenadante y lavar las perlas de GST con P5 bufFer (50 mM NaHPO 4 pH 7,0, NaCl 500 mM, 10% de glicerol, 0,05% de Triton-X-100, imidazol 5 mM). </li><li> Incubar las GST-cuentas con enzima PreScission en tampón P5 de 3 horas a la noche a 4 ° C. (Divida las perlas de GST en fracciones de 100 l y agregue 4-8 unidades (2-4 mu l) de la enzima diluida en 100 l de tampón P5). </li></ol> Comentario: El tiempo de incubación de la etapa de PreScission debe ser optimizado de acuerdo con el peso molecular, así como la estabilidad de la proteína. Si se observa la degradación, este tiempo de incubación se puede disminuir a un mínimo de 2 horas en lugar de durante la noche. <ol start="3"><li> Un paseo rápido y recoger el sobrenadante. Repita este paso dos veces después de la adición de 100 l de P5 amortiguar hasta el talón y aunar todas las fracciones (Figura 3B, carril 2). </li></ol> Comentario: Las perlas restantes pueden ser utilizados para el análisis de la eficacia de escisión (Figura 3B </strong&gt;, carril 3). Por lo general, 70-80% de la proteína se escinde. 6. A TALON metal Affinity Resin La unión a proteínas- <ol><li> Divida la elución desde arriba en 3 fracciones de 1 ml e incubar cada uno con 100 perlas secas de resina de afinidad de metal Talon mu l (prelavadas dos veces con tampón de P5) durante 1 hora bajo rotación. </li></ol> Comentario: La división de la elución en varias fracciones aumenta la eficiencia de unión / lavados. <ol start="2"><li> Lavar la resina 5 min con tampón de P30 (tampón P5 con una concentración final de imidazol 30 mM). </li><li> Repita el paso 6.2 2x y agrupar las cuentas en un solo tubo. Antes de que el último lavado, eliminar la mayor cantidad sobrenadante como sea posible. </li></ol> Comentario: Esto corresponde a la TALON unido de la muestra (Figura 3B, carril 4). 7. La elución de la proteína purificada <ol><li> Se incuba la proteína unida a resina TALON durante 5 min en rotación con P500 tampón (tampón P5 con una concentración final de imidazol 500 mM). Utilice una relación entre la memoria y cuentas de 1:1 v / v (Por ejemplo, si usted ha tomado 200 l de granos secos, usted tendrá que añadir 200 l de P500). Repita este paso dos veces y mantener cada fracción eluida por separado (llamado elución 1 (E1), elución 2 (E2) y la elución 3 (E3); Figura 3B, carriles 5-7). </li></ol> Comentario: Las perlas restantes pueden ser utilizados para el análisis de la eficiencia de elución (Figura 3B, pista 8). Típicamente, un 60-80% de la proteína se eluye en total. <ol start="2"><li> Analizar la cantidad y la calidad de su proteína purificada por la carga de aproximadamente 20-40 l de cada fracción con una concentración patrón de BSA en un SDS-PAGE y tinción con azul de Coomassie (Figura 3B) o SYPRO tinción de proteínas para la visualización. </li></ol> Comentario: La proteína de interés se puede detectar también excelentes referenciasughout el procedimiento de purificación utilizando anti-GST y anticuerpos anti-His (Figura 3C). 8. El almacenamiento de la proteína purificada <ol><li> Se dializa la proteína purificada contra un tampón de almacenamiento apropiado (por ejemplo 20 mM de Tris Acetato pH 8,0, 200 mM de KAc, 10% de glicerol, EDTA 1 mM, DTT 0,5 mM) a 4 ° C. Es importante comprobar la precipitación de la proteína purificada durante la diálisis. Por lo general, diálisis a 2x durante 1 hora a 4 ° C bajo rotación agitación. </li><li> Hacer pequeñas alícuotas de la proteína purificada (10-20 l) y la congelación en hielo seco durante 30 min. Almacene las alícuotas a -80 ° C y evitar muchos ciclos de descongelación / congelación. </li></ol>

<ol>
	<li>Lichty, J. J., Malecki, J. L., Agnew, H. D., Michelson-Horowitz, D. J., Tan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+affinity+tags+for+protein+purification.">Comparison of affinity tags for protein purification.</a> Protein Expr. Purif. 41, 98-105 (2005).</li><li>Thain, A., Gaston, K., Jenkins, O., Clarke, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+the+separation+of+GST+fusion+proteins+from+co-purifying+GroEL.">A method for the separation of GST fusion proteins from co-purifying GroEL.</a> Trends Genet. 12, 209-210 (1996).</li><li>Carr, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+a+recombinant+form+of+the+V+antigen+of+Yersinia+pestis,+using+three+different+expression+systems.">Expression of a recombinant form of the V antigen of Yersinia pestis, using three different expression systems.</a> Vaccine. 18, 153-159 (1999).</li><li>Armisen, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+adsorption+of+poly-His+tagged+glutaryl+acylase+on+tailor-made+metal+chelate+supports.">Selective adsorption of poly-His tagged glutaryl acylase on tailor-made metal chelate supports.</a> J. Chromatogr. A. 848, 61-70 (1999).</li><li>Kuhn, S., Zipfel, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+baculovirus+expression+vector+pBSV-8His+directs+secretion+of+histidine-tagged+proteins.">The baculovirus expression vector pBSV-8His directs secretion of histidine-tagged proteins.</a> Gene. 162, 225-229 (1995).</li><li>Buisson, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cooperation+of+breast+cancer+proteins+PALB2+and+piccolo+BRCA2+in+stimulating+homologous+recombination.">Cooperation of breast cancer proteins PALB2 and piccolo BRCA2 in stimulating homologous recombination.</a> Nat. Struct. Mol. Biol. 17, 1247-1254 (2010).</li><li>Filimonova, M. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isoforms+of+Serratia+marcescens+nuclease.+The+role+of+Mg2++in+the+hydrolysis+mechanism.">Isoforms of Serratia marcescens nuclease. The role of Mg2+ in the hydrolysis mechanism.</a> Biochemistry. 62, 983-988 (1997).</li><li>Thorslund, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+breast+cancer+tumor+suppressor+BRCA2+promotes+the+specific+targeting+of+RAD51+to+single-stranded+DNA.">The breast cancer tumor suppressor BRCA2 promotes the specific targeting of RAD51 to single-stranded DNA.</a> Nat. Struct. Mol. Biol. 17, 1263-1265 (2010).</li><li>Genois, M. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactions+between+BRCA2+and+RAD51+for+promoting+homologous+recombination+in+Leishmania+infantum.">Interactions between BRCA2 and RAD51 for promoting homologous recombination in Leishmania infantum.</a> Nucleic Acids Res. 40, 6570-6584 (2012).</li><li>Shrestha, B., Smee, C., Gileadi, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Baculovirus+expression+vector+system:+an+emerging+host+for+high-throughput+eukaryotic+protein+expression.">Baculovirus expression vector system: an emerging host for high-throughput eukaryotic protein expression.</a> Methods Mol. Biol. 439, 269-289 (2008).</li></ol>

El GST-Su protocolo de purificación que aquí se presenta es adecuado para la purificación de una amplia gama de tamaños de proteínas recombinantes: Se purificaron con éxito Li RAD51 (41kDa), piBRCA2 (120 kDa), PALB2 (130kDa), y una proteína de alto peso molecular inestable peso de Leishmania infantum: Li BRCA2 (125kDa) 6,9. Por otra parte, las proteínas purificadas con este protocolo eran bioquímicamente activa 6. El éxito de este método depende únicamente de la expres...

La purificación de proteínas recombinantes es crucial para hacer frente a cuestiones fundamentales de la bioquímica. Formas convencionales de purificación de proteínas, como la cromatografía de intercambio iónico y cromatografía de exclusión por tamaños se basan en las propiedades físicas de la proteína diana, como su punto isoeléctrico y la carga o el tamaño, respectivamente. Las características de proteínas últimos son compartidos por una variedad de proteínas, lo que aumenta considerablemente la probabilidad de proteínas contaminantes en las estrategias de purificación de proteínas convencionales. Este problema puede ser evitado con el uso de múltiples columnas de purificación, lo que consume tiempo. Al mismo tiempo, los métodos de cromatografía de éstos exigen configuración experimental caro. La purificación por afinidad-etiqueta aumenta fuertemente objetivo-especificidad, como en la mayoría de los casos la etiqueta será único para la proteína de interés. En estudios recientes, la purificación de la bandera-o HA-afinidad se ha usado ampliamente. En contraste con rec existenteprotocolos de purificación de proteínas ombinant en la que se utilizan etiquetas individuales, se estableció la combinación única de dos etiquetas. Nuestro método implica la fusión de una etiqueta de GST en el extremo N-terminal y una etiqueta de His en el extremo C-terminal de la proteína de interés, para una relación óptima entre la cantidad y la pureza de la proteína deseada. El GST es un largo etiqueta (29 kDa), que es altamente eficiente para la purificación sobre glutatión Sepharose bolas. Por otra parte, el uso de GST garantiza la rentabilidad de nuestro método 1. La posibilidad de escindir la GST con la enzima PreScission (con secuencia de reconocimiento de LeuGluValLeuPheGln / GlyPro, lo que resulta en la adición de sólo dos aminoácidos) tiene muchas ventajas, por ejemplo, esta estrategia evita alteraciones de las funciones de las proteínas fisiológicas debido al impedimento alostérico. La pequeña etiqueta de His fusionada a la otra extremidad de proteína sirve en una segunda etapa de purificación para aumentar la pureza de proteína mediante el lavado de la GST escindido, así como las proteínas degradadas y otra<html> contaminantes. Además, el protocolo no requiere una etapa de diálisis cuando se cambia de la GST para columnas de paso de la Su-purificación (resina TALON). Contaminantes comunes en este tipo de procesos de purificación son proteínas de choque térmico (HSP). La adición de una etapa de incubación con MgCl 2 y ATP permite la eliminación de estos contaminantes (Figura 1). Fast Protein Liquid Chromatography (FPLC) y cromatografía líquida de alta resolución (HPLC) son técnicas comunes que dependen de instrumentación costosa de generar un alto rendimiento de la proteína purificada de interés. El protocolo de purificación de lotes se presenta aquí, en contraste, es manual y no requiere una configuración de instrumento caro. Un alto rendimiento de proteína se puede llegar por la ampliación del protocolo. Al mismo tiempo, con el protocolo de purificación de lotes, el volumen de elución se puede ajustar con el fin de mejorar la concentración de proteína, que no se da con FPLC o HPLC. ntent &quot;&gt; También, con el GST-Su protocolo de purificación por lotes, las proteínas con un tamaño de rango de ~ 10-300 kDa pueden purificarse. Una de las mayores ventajas es dada por el hecho de que uno puede purificar varias proteínas al mismo tiempo , por ejemplo, tanto una de tipo salvaje y su proteína mutante. El éxito del protocolo presentado depende únicamente en el nivel de expresión y la solubilidad de la proteína de interés.

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>REAGENTS</td>
		</tr>
		<tr>
			<td>E.Coli DH10Bac (competent)</td>
			<td>Invitrogen</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bac-to-Bac Baculovirus Expression System</td>
			<td>Invitrogen</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Maxi Prep Kit</td>
			<td>Qiagen</td>
			<td>12163</td>
			<td>Solution I and II</td>
		</tr>
		<tr>
			<td>Ultra Pure Bluo-Gal</td>
			<td>Gibco (Life)</td>
			<td>15519028</td>
			<td></td>
		</tr>
		<tr>
			<td>IPTG</td>
			<td>Gibco (Life)</td>
			<td>15529019</td>
			<td></td>
		</tr>
		<tr>
			<td>Sf9 infected cells</td>
			<td>ATCC</td>
			<td>CRL-1711</td>
			<td></td>
		</tr>
		<tr>
			<td>PreScission enzyme</td>
			<td>GE Healthcare</td>
			<td>27084301</td>
			<td></td>
		</tr>
		<tr>
			<td>Grace&#39;s infected medium supplemented</td>
			<td>Gibco (Life)</td>
			<td>11605-094</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum characterized</td>
			<td>Hyclone</td>
			<td>SH30396.03</td>
			<td></td>
		</tr>
		<tr>
			<td>P/S (Penicillin-Streptomycin)</td>
			<td>Gibco (Life)</td>
			<td>15070-063</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutathione Sepharose resin</td>
			<td>GE bioscience</td>
			<td>17075605</td>
			<td></td>
		</tr>
		<tr>
			<td>Protease inhibitor cocktail</td>
			<td>Roche</td>
			<td>11873580001</td>
			<td></td>
		</tr>
		<tr>
			<td>Talon resin</td>
			<td>Clontech</td>
			<td>635504</td>
			<td></td>
		</tr>
		<tr>
			<td>Imidazole</td>
			<td>BioShop</td>
			<td>288324</td>
			<td></td>
		</tr>
		<tr>
			<td>Gentamicin</td>
			<td>Gibco (Life)</td>
			<td>15710064</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyclonal GST-antibody</td>
			<td>Production in house</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Monoclonal 6X-His-antibody</td>
			<td>Clontech</td>
			<td>631212</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>EQUIPMENT</td>
		</tr>
		<tr>
			<td>Dounce homogenizer (tight)</td>
			<td>Wheaton</td>
			<td>357546</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator (Fisher dismembrator)</td>
			<td>Fisher</td>
			<td>Model 150</td>
			<td></td>
		</tr>
		<tr>
			<td>Dialysis bag (50 mm)</td>
			<td>Fisher Scientific</td>
			<td>2115217</td>
			<td></td>
		</tr>
	</tbody>
</table>

gst-his purification: a two-step affinity purification protocol yielding full-length purified proteins

Ensayos de clave en enzimología para la caracterización bioquímica de las proteínas in vitro requieren altas concentraciones de la proteína purificada de interés. Protocolos de purificación de proteínas deben combinar eficiencia, simplicidad y rentabilidad 1. Aquí, describimos la GST-Su método como un nuevo sistema de purificación por afinidad a pequeña escala para proteínas recombinantes, sobre la base de un N-terminal de la etiqueta glutatión Sepharose (GST) 2,3 y una etiqueta 10xHis C-terminal 4, que tanto se fusionan a la proteína de interés. La última construcción se utiliza para generar baculovirus, para la infección de las células Sf9 infectadas para la expresión de proteínas 5. GST es una etiqueta bastante largo (29 kDa), que sirve para asegurar la eficacia de la purificación. Sin embargo, podría influir en las propiedades fisiológicas de la proteína. Por lo tanto, en que posteriormente se escinde la proteína usando la enzima PreScission 6. Con el fin de garantizar la máxima pureza y para eliminar el GST escindido, nosañadido una segunda etapa de purificación de afinidad basada en la comparativamente pequeña etiqueta de His. Es importante destacar que, nuestra técnica se basa en dos etiquetas diferentes que flanquean los dos extremos de la proteína, que es una herramienta eficaz para eliminar las proteínas degradadas y, por lo tanto, enriquece proteínas de longitud completa. El método que aquí se presenta no requiere una configuración fundamental caros, tales como FPLC. Además, incorporamos MgCl 2 y lavados ATP para eliminar las impurezas de la proteína de choque de calor y tratamiento con nucleasa de abolir ácidos nucleicos contaminantes. En resumen, la combinación de dos etiquetas diferentes que flanquean el N-y C-terminal y la capacidad de escindir una de las etiquetas, garantiza la recuperación de una proteína altamente purificada y de longitud completa de interés.

Con el fin de ilustrar la eficiencia de la GST-Su protocolo de purificación, purificamos Rec14, un S. pombe proteína de 32,9 kDa. El cDNA fue clonado Rec14 en nuestro vector pFastBac1 modificado que permite la adición de GST-y sus etiquetas en el extremo N-y C-terminales, respectivamente (Figura 1 A). El baculovirus recombinante se prepararon entonces y se utilizan para infectar células SF9 infectadas para la expresión de proteínas. Los lisados ​​celulares solubles se incubaron con pe...

Watch this Scientific Journal Video about GST-His purification: A Two-step Affinity Purification Protocol Yielding Full-length Purified Proteins at JoVE.com

GST-His purification: A Two-step Affinity Purification Protocol Yielding Full-length Purified Proteins

En el presente protocolo, se demuestra un método de purificación de proteínas a pequeña escala altamente eficiente y rentable, que permite la purificación de proteínas recombinantes, combinando de forma única una etiqueta de GST escindible y una pequeña cola de His.

GST-Su purificación: A dos pasos Affinity Protocolo Purificación Cediendo largos proteínas purificadas

Key assays in enzymology for the biochemical characterization of proteins in vitro necessitate high concentrations of the purified protein of interest. ...

gst-his-purification-two-step-affinity-purification-protocol-yielding

Research

JoVE Journal

Biology

41.1K vistas.  Hôtel-Dieu de Québec.  En el presente protocolo, se demuestra un método de purificación de proteínas a pequeña escala altamente eficiente y rentable, que permite la purificación de proteínas recombinantes, combinando de forma única una etiqueta de GST escindible y una pequeña cola de His. 

Video: GST-His purification: A Two-step Affinity Purification Protocol Yielding Full-length Purified Proteins

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents (Methanol, Ethanol or 2-Propanol) and acetic acid are used for fixation, staining and destaining of proteins in a gel after SDS-PAGE. To speed up the procedure, heating the staining solution in the microwave oven for a short time is frequently used. This usually results in evaporation of toxic or hazardous Methanol, Ethanol or 2-Propanol and a strong smell of acetic acid in the lab which should be avoided due to safety considerations. In a protocol originally published in two patent applications by E.M. Wondrak (US2001046709 (A1), US6319720 (B1)), an alternative composition of the staining solution is described in which no organic solvent or acid is used. The CBB is dissolved in bidistilled water (60-80mg of CBB G-250 per liter) and 35 mM HCl is added as the only other compound in the staining solution. The CBB staning of the gel is done after SDS-PAGE and thorough washing of the gel in bidistilled water. By heating the gel during the washing and staining steps, the process can be finished faster and no toxic or hazardous compunds are evaporating. The staining of proteins occurs already within 1 minute after heating the gel in staining solution and is fully developed after 15-30 min with a slightly blue background that is destained completely by prolonged washing of the stained gel in bidistilled water, without affecting the stained protein bands.

A short protocol for protein staining with Coomassie Brilliant Blue (CBB) G-250 in polyacrylamide gels is described without using organic solvents or acetic acid as in the classical staining procedures with CBB.

Tinción de las proteínas en geles con Coomassie G-250, sin ácido disolvente orgánico y el acético

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Investigación

Biología

Purification of Hsp104, a Protein Disaggregase

Hsp104 is a hexameric AAA+ protein1 from yeast, which couples ATP hydrolysis to protein disaggregation2-10 (Fig. 1). This activity imparts two key selective advantages. First, renaturation of disordered aggregates by Hsp104 empowers yeast survival after various protein-misfolding stresses, including heat shock3,5,11,12. Second, remodeling of cross-beta amyloid fibrils by Hsp104 enables yeast to exploit myriad prions (infectious amyloids) as a reservoir of beneficial and heritable phenotypic variation13-22. Remarkably, Hsp104 directly remodels preamyloid oligomers and amyloid fibrils, including those comprised of the yeast prion proteins Sup35 and Ure223-30. This amyloid-remodeling functionality is a specialized facet of yeast Hsp104. The E. coli orthologue, ClpB, fails to remodel preamyloid oligomers or amyloid fibrils26,31,32.
Hsp104 orthologues are found in all kingdoms of life except, perplexingly, animals. Indeed, whether animal cells possess any enzymatic system that couples protein disaggregation to renaturation (rather than degradation) remains unknown33-35. Thus, we and others have proposed that Hsp104 might be developed as a therapeutic agent for various neurodegenerative diseases connected with the misfolding of specific proteins into toxic preamyloid oligomers and amyloid fibrils4,7,23,36-38. There are no treatments that directly target the aggregated species associated with these diseases. Yet, Hsp104 dissolves toxic oligomers and amyloid fibrils composed of alpha-synuclein, which are connected with Parkinson's Disease23 as well as amyloid forms of PrP39. Importantly, Hsp104 reduces protein aggregation and ameliorates neurodegeneration in rodent models of Parkinson's Disease23 and Huntington's disease38. Ideally, to optimize therapy and minimize side effects, Hsp104 would be engineered and potentiated to selectively remodel specific aggregates central to the disease in question4,7. However, the limited structural and mechanistic understanding of how Hsp104 disaggregates such a diverse repertoire of aggregated structures and unrelated proteins frustrates these endeavors30,40-42.
To understand the structure and mechanism of Hsp104, it is essential to study the pure protein and reconstitute its disaggregase activity with minimal components. Hsp104 is a 102kDa protein with a pI of ~5.3, which hexamerizes in the presence of ADP or ATP, or at high protein concentrations in the absence of nucleotide43-46. Here, we describe an optimized protocol for the purification of highly active, stable Hsp104 from E. coli. The use of E. coli allows simplified large-scale production and our method can be performed quickly and reliably for numerous Hsp104 variants. Our protocol increases Hsp104 purity and simplifies His6-tag removal compared to a previous purification method from E. coli47. Moreover, our protocol is more facile and convenient than two more recent protocols26,48.

Here, we describe a protocol for the purification of highly active Hsp104, a hexameric AAA+ protein from yeast, which couples ATP hydrolysis to protein disaggregation. This scheme exploits a His6-tagged construct for affinity purification from E. coli followed by anion-exchange chromatography, His6-tag removal with TEV protease, and size-exclusion chromatography.

La purificación de Hsp104, una proteína Disaggregase

Hsp104 is a hexameric AAA+ protein1 from yeast, which couples ATP hydrolysis to protein disaggregation2-10 (Fig. 1). This activity imparts two key ...

Chromatographic Purification of Highly Active Yeast Ribosomes

Eukaryotic ribosomes are much more labile as compared to their eubacterial and archael counterparts, thus posing a significant challenge to researchers. Particularly troublesome is the fact that lysis of cells releases a large number of proteases and nucleases which can degrade ribosomes. Thus, it is important to separate ribosomes from these enzymes as quickly as possible. Unfortunately, conventional differential ultracentrifugation methods leaves ribosomes exposed to these enzymes for unacceptably long periods of time, impacting their structural integrity and functionality. To address this problem, we utilize a chromatographic method using a cysteine charged Sulfolink resin. This simple and rapid application significantly reduces co-purifying proteolytic and nucleolytic activities, producing high yields of intact, highly biochemically active yeast ribosomes. We suggest that this method should also be applicable to mammalian ribosomes. The simplicity of the method, and the enhanced purity and activity of chromatographically purified ribosome represents a significant technical advancement for the study of eukaryotic ribosomes.

Contamination of preparations of eukaryotic ribosomes purified by traditional methods by co-purifying nucleases and proteases negatively impacts on downstream biochemical and structural analyses. A rapid and simple chromatographic purification method is used to solve this problem using yeast ribosomes as a model system.

Purificación por cromatografía de ribosomas de levadura de gran actividad

Eukaryotic ribosomes are much more labile as compared to their eubacterial and archael counterparts, thus posing a significant challenge to researchers.  ...

Orthogonal Protein Purification Facilitated by a Small Bispecific Affinity Tag

Due to the high costs associated with purification of recombinant proteins the protocols need to be rationalized. For high-throughput efforts there is a demand for general methods that do not require target protein specific optimization1 . To achieve this, purification tags that genetically can be fused to the gene of interest are commonly used2 . The most widely used affinity handle is the hexa-histidine tag, which is suitable for purification under both native and denaturing conditions3 . The metabolic burden for producing the tag is low, but it does not provide as high specificity as competing affinity chromatography based strategies1,2.
Here, a bispecific purification tag with two different binding sites on a 46 amino acid, small protein domain has been developed. The albumin-binding domain is derived from Streptococcal protein G and has a strong inherent affinity to human serum albumin (HSA). Eleven surface-exposed amino acids, not involved in albumin-binding4 , were genetically randomized to produce a combinatorial library. The protein library with the novel randomly arranged binding surface (Figure 1) was expressed on phage particles to facilitate selection of binders by phage display technology. Through several rounds of biopanning against a dimeric Z-domain derived from Staphylococcal protein A5, a small, bispecific molecule with affinity for both HSA and the novel target was identified6 .
The novel protein domain, referred to as ABDz1, was evaluated as a purification tag for a selection of target proteins with different molecular weight, solubility and isoelectric point. Three target proteins were expressed in Escherishia coli with the novel tag fused to their N-termini and thereafter affinity purified. Initial purification on either a column with immobilized HSA or Z-domain resulted in relatively pure products. Two-step affinity purification with the bispecific tag resulted in substantial improvement of protein purity. Chromatographic media with the Z-domain immobilized, for example MabSelect SuRe, are readily available for purification of antibodies and HSA can easily be chemically coupled to media to provide the second matrix.
This method is especially advantageous when there is a high demand on purity of the recovered target protein. The bifunctionality of the tag allows two different chromatographic steps to be used while the metabolic burden on the expression host is limited due to the small size of the tag. It provides a competitive alternative to so called combinatorial tagging where multiple tags are used in combination1,7.

A novel and highly efficient two-step affinity chromatography protocol has been developed and is described in detail. The method is based on a small purification tag with two inherent affinities and is applicable to a wide range of target proteins with different properties.

Purificación de proteínas ortogonales Facilitado por un marcador de afinidad biespecíficos pequeños

Due to the high costs associated with purification of recombinant proteins the protocols need to be rationalized. For high-throughput efforts there is a ...

Identification of Protein Interacting Partners Using Tandem Affinity Purification

A critical and often limiting step in understanding the function of host and viral proteins is the identification of interacting cellular or viral protein partners. There are many approaches that allow the identification of interacting partners, including the yeast two hybrid system, as well as pull down assays using recombinant proteins and immunoprecipitation of endogenous proteins followed by mass spectrometry identification1. Recent studies have highlighted the utility of double-affinity tag mediated purification, coupled with two specific elution steps in the identification of interacting proteins. This approach, termed Tandem Affinity Purification (TAP), was initially used in yeast2,3 but more recently has been adapted to use in mammalian cells4-8.
As proof-of-concept we have established a tandem affinity purification (TAP) method using the well-characterized eukaryotic translation initiation factor eIF4E9,10.The cellular translation factor eIF4E is a critical component of the cellular eIF4F complex involved in cap-dependent translation initiation10. The TAP tag used in the current study is composed of two Protein G units and a streptavidin binding peptide separated by a Tobacco Etch Virus (TEV) protease cleavage sequence. The TAP tag used in the current study is composed of two Protein G units and a streptavidin binding peptide separated by a Tobacco Etch Virus (TEV) protease cleavage sequence8. To forgo the need for the generation of clonal cell lines, we developed a rapid system that relies on the expression of the TAP-tagged bait protein from an episomally maintained plasmid based on pMEP4 (Invitrogen). Expression of tagged murine eIF4E from this plasmid was controlled using the cadmium chloride inducible metallothionein promoter.
Lysis of the expressing cells and subsequent affinity purification via binding to rabbit IgG agarose, TEV protease cleavage, binding to streptavidin linked agarose and subsequent biotin elution identified numerous proteins apparently specific to the eIF4E pull-down (when compared to control cell lines expressing the TAP tag alone). The identities of the proteins were obtained by excision of the bands from 1D SDS-PAGE and subsequent tandem mass spectrometry. The identified components included the known eIF4E binding proteins eIF4G and 4EBP-1. In addition, other components of the eIF4F complex, of which eIF4E is a component were identified, namely eIF4A and Poly-A binding protein. The ability to identify not only known direct binding partners as well as secondary interacting proteins, further highlights the utility of this approach in the characterization of proteins of unknown function.

Tandem affinity purification is a robust approach for the identification of protein binding partners. As proof of concept, this methodology was applied to the well-characterized translation initiation factor eIF4E to co-precipitate the host cell factors involved in translation initiation. This method is easily adapted to any cellular or viral protein.

Identificación de los socios interacción de proteínas en tándem de purificación de afinidad

A critical and often limiting step in understanding the function of host and viral proteins is the identification of interacting cellular or viral protein ...

High-throughput Purification of Affinity-tagged Recombinant Proteins

X-ray crystallography is the method of choice for obtaining a detailed view of the structure of proteins. Such studies need to be complemented by further biochemical analyses to obtain detailed insights into structure/function relationships. Advances in oligonucleotide- and gene synthesis technology make large-scale mutagenesis strategies increasingly feasible, including the substitution of target residues by all 19 other amino acids. Gain- or loss-of-function phenotypes then allow systematic conclusions to be drawn, such as the contribution of particular residues to catalytic activity, protein stability and/or protein-protein interaction specificity.
In order to attribute the different phenotypes to the nature of the mutation - rather than to fluctuating experimental conditions - it is vital to purify and analyse the proteins in a controlled and reproducible manner. High-throughput strategies and the automation of manual protocols on robotic liquid-handling platforms have created opportunities to perform such complex molecular biological procedures with little human intervention and minimal error rates1-5.
Here, we present a general method for the purification of His-tagged recombinant proteins in a high-throughput manner. In a recent study, we applied this method to a detailed structure-function investigation of TFIIB, a component of the basal transcription machinery. TFIIB is indispensable for promoter-directed transcription in vitro and is essential for the recruitment of RNA polymerase into a preinitiation complex6-8. TFIIB contains a flexible linker domain that penetrates the active site cleft of RNA polymerase9-11. This linker domain confers two biochemically quantifiable activities on TFIIB, namely (i) the stimulation of the catalytic activity during the 'abortive' stage of transcript initiation, and (ii) an additional contribution to the specific recruitment of RNA polymerase into the preinitiation complex4,5,12 . We exploited the high-throughput purification method to generate single, double and triple substitution and deletions mutations within the TFIIB linker and to subsequently analyse them in functional assays for their stimulation effect on the catalytic activity of RNA polymerase4. Altogether, we generated, purified and analysed 381 mutants - a task which would have been time-consuming and laborious to perform manually. We produced and assayed the proteins in multiplicates which allowed us to appreciate any experimental variations and gave us a clear idea of the reproducibility of our results.
This method serves as a generic protocol for the purification of His-tagged proteins and has been successfully used to purify other recombinant proteins. It is currently optimised for the purification of 24 proteins but can be adapted to purify up to 96 proteins.

We describe a method for the affinity-tagged purification of recombinant proteins using liquid-handling robotics. This method is generally applicable to the small-scale purification of soluble His-tagged proteins in a high-throughput format.

De alto rendimiento de purificación de afinidad de proteínas marcadas con recombinantes

X-ray crystallography is the method of choice for obtaining a detailed view of the structure of proteins. Such studies need to be complemented by further ...

Protein Purification-free Method of Binding Affinity Determination by Microscale Thermophoresis

Quantitative characterization of protein interactions is essential in practically any field of life sciences, particularly drug discovery. Most of currently available methods of KD determination require access to purified protein of interest, generation of which can be time-consuming and expensive. We have developed a protocol that allows for determination of binding affinity by microscale thermophoresis (MST) without purification of the target protein from cell lysates. The method involves overexpression of the GFP-fused protein and cell lysis in non-denaturing conditions. Application of the method to STAT3-GFP transiently expressed in HEK293 cells allowed to determine for the first time the affinity of the well-studied transcription factor to oligonucleotides with different sequences. The protocol is straightforward and can have a variety of application for studying interactions of proteins with small molecules, peptides, DNA, RNA, and proteins.

Microscale thermophoresis (MST) can be widely used for determination of binding affinity without purification of the target protein from cell lysates. The protocol involves overexpression of the GFP-fused protein, cell lysis in non-denaturing conditions, and detection of MST signal in the presence of varying concentrations of the ligand.

Purificación de proteínas libre de Método de Determinación afinidad de unión por termoforesis Microscale

Quantitative characterization of protein  interactions is essential in practically any field of life sciences,  particularly drug discovery. Most of ...

A Protocol for Phage Display and Affinity Selection Using Recombinant Protein Baits

Using recombinant phage as a scaffold to present various protein portions encoded by a directionally cloned cDNA library to immobilized bait molecules is an efficient means to discover interactions. The technique has largely been used to discover protein-protein interactions but the bait molecule to be challenged need not be restricted to proteins. The protocol presented here has been optimized to allow a modest number of baits to be screened in replicates to maximize the identification of independent clones presenting the same protein. This permits greater confidence that interacting proteins identified are legitimate interactors of the bait molecule. Monitoring the phage titer after each affinity selection round provides information on how the affinity selection is progressing as well as on the efficacy of negative controls. One means of titering the phage, and how and what to prepare in advance to allow this process to progress as efficiently as possible, is presented. Attributes of amplicons retrieved following isolation of independent plaque are highlighted that can be used to ascertain how well the affinity selection has progressed. Trouble shooting techniques to minimize false positives or to bypass persistently recovered phage are explained. Means of reducing viral contamination flare up are discussed.

Phage display is a powerful technique to capture proteins or protein moieties that interact with an immobilized molecule of interest. Once a decision of the type of phage cDNA library to create and screen has been made, the protocol described here permits efficient affinity selection leading to identification of interactors.

Un Protocolo de fagos y de selección de afinidad utilizando cebos proteína recombinante

Using  recombinant phage as a scaffold to present various protein portions encoded by  a directionally cloned cDNA library to immobilized bait molecules ...

Identifying Protein-protein Interaction in Drosophila Adult Heads by Tandem Affinity Purification (TAP)

Genetic screens conducted using Drosophila melanogaster (fruit fly) have made numerous milestone discoveries in the advance of biological sciences. However, the use of biochemical screens aimed at extending the knowledge gained from genetic analysis was explored only recently. Here we describe a method to purify the protein complex that associates with any protein of interest from adult fly heads. This method takes advantage of the Drosophila GAL4/UAS system to express a bait protein fused with a Tandem Affinity Purification (TAP) tag in fly neurons in vivo, and then implements two rounds of purification using a TAP procedure similar to the one originally established in yeast1 to purify the interacting protein complex. At the end of this procedure, a mixture of multiple protein complexes is obtained whose molecular identities can be determined by mass spectrometry. Validation of the candidate proteins will benefit from the resource and ease of performing loss-of-function studies in flies. Similar approaches can be applied to other fly tissues. We believe that the combination of genetic manipulations and this proteomic approach in the fly model system holds tremendous potential for tackling fundamental problems in the field of neurobiology and beyond.

Identifying Protein-protein Interaction in Drosophila Adult Heads by Tandem Affinity Purification TAP

Drosophila is famous for its powerful genetic manipulation, but not for its suitability of in-depth biochemical analysis. Here we present a TAP-based procedure to identify interacting partners of any protein of interest from the fly brain. This procedure can potentially lead to new avenues of research.

La identificación de la interacción proteína-proteína en<em&gt; Drosophila</em&gt; Jefes adultas por Tandem Affinity purificación (TAP)

Genetic screens conducted using Drosophila melanogaster (fruit fly) have made numerous milestone discoveries in the advance of biological sciences. ...

Protein Purification Technique that Allows Detection of Sumoylation and Ubiquitination of Budding Yeast Kinetochore Proteins Ndc10 and Ndc80

Post-translational Modifications (PTMs), such as phosphorylation, methylation, acetylation, ubiquitination, and sumoylation, regulate the cellular function of many proteins. PTMs of kinetochore proteins that associate with centromeric DNA mediate faithful chromosome segregation to maintain genome stability. Biochemical approaches such as mass spectrometry and western blot analysis are most commonly used for identification of PTMs. Here, a protein purification method is described that allows the detection of both sumoylation and ubiquitination of the kinetochore proteins, Ndc10 and Ndc80, in Saccharomyces cerevisiae. A strain that expresses polyhistidine-Flag-tagged Smt3 (HF-Smt3) and Myc-tagged Ndc10 or Ndc80 was constructed and used for our studies. For detection of sumoylation, we devised a protocol to affinity purify His-tagged sumoylated proteins by using nickel beads and used western blot analysis with anti-Myc antibody to detect sumoylated Ndc10 and Ndc80. For detection of ubiquitination, we devised a protocol for immunoprecipitation of Myc-tagged proteins and used western blot analysis with anti-Ub antibody to show that Ndc10 and Ndc80 are ubiquitinated. Our results show that epitope tagged-protein of interest in the His-Flag tagged Smt3 strain facilitates the detection of multiple PTMs. Future studies should allow exploitation of this technique to identify and characterize protein interactions that are dependent on a specific PTM.

This manuscript describes the detection of sumoylation and ubiquitination of kinetochore proteins, Ndc10 and Ndc80, in the budding yeast Saccharomyces cerevisiae.