Name: efficient and site-specific antibody labeling by strain-promoted azide-alkyne cycloaddition
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1. Plasmid Construction
<ol>
	<li>Construct an expression plasmid (pBAD-HerFab-L177TAG) that would express the target antibody gene (pBAD-HerFab-WT) with a His6-tag, and replace the codon for Leucine-177 with the amber codon (TAG) 27, using conventional site-directed mutagenesis technique. 
	See Table of Materials.</li>
	<li>Construct another expression plasmid (pEVOL-AFRS) containing the genes for the evolved tRNATyr and aminoacyl-tRNA synthetase (aaRS) pair. Use ...

<ol>
	<li>Wang, L., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expanding+the+genetic+code.">Expanding the genetic code.</a> Angew. Chem. Int. Ed. 44 (1), 34-66 (2004).</li><li>Wu, X., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+at+the+interface+of+chemistry+and+biology.">Synthesis at the interface of chemistry and biology.</a> J. Am. Chem. Soc. 131 (35), 12497-12515 (2009).</li><li>Liu, C. C., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adding+new+chemistries+to+the+genetic+code.">Adding new chemistries to the genetic code.</a> Annu. Rev. Biochem. 79, 413-444 (2010).</li><li>Wang, L., Zhang, Z., Brock, A., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Addition+of+the+keto+functional+groupto+the+genetic+code+of+Escherichia+coli.">Addition of the keto functional groupto the genetic code of Escherichia coli.</a> proc. Natl. Acad. Sci. U.S.A. 100 (1), 56-61 (2003).</li><li>Chin, J. W., 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=Addition+of+p-azido-L-phenylalanine+to+the+genetic+code+of+Escherichia+coli.">Addition of p-azido-L-phenylalanine to the genetic code of Escherichia coli.</a> J. Am. Chem. Soc. 124 (31), 9026-9027 (2002).</li><li>Deiters, A., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+incorporation+of+an+alkyne+into+proteins+in+Esshcerichia+coli.">In vivo incorporation of an alkyne into proteins in Esshcerichia coli.</a> Bioorg. Med. Chem. Lett. 15 (5), 1521-1524 (2005).</li><li>Plass, T., Milles, S., Koehler, C., Schultz, C., Lemke, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+encoded+copper-free+click+chemistry.">Genetically encoded copper-free click chemistry.</a> Angew. Chem. Int. Ed. 50 (17), 3878-3881 (2011).</li><li>Seitchik, J. L., 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=Genetically+encoded+tetrazine+amino+acid+directs+rapid+site-specific+in+vivo+bioorthogonal+ligation+with+transcyclooctenes.">Genetically encoded tetrazine amino acid directs rapid site-specific in vivo bioorthogonal ligation with transcyclooctenes.</a> J. Am. Chem. Soc. 134 (6), 2898-2901 (2014).</li><li>Lee, Y. -. J., 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=A+genetically+encoded+acrylamide+fuctionality.">A genetically encoded acrylamide fuctionality.</a> ACS Chem. Biol. 8 (8), 1664-1670 (2013).</li><li>Lang, K., 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=Genetically+encoded+norbornene+directs+site-specific+cellular+protein+labelling+via+a+rapid+bioorthogonal+raction.">Genetically encoded norbornene directs site-specific cellular protein labelling via a rapid bioorthogonal raction.</a> Nat Chem. 4 (4), 298-304 (2012).</li><li>Lang, K., 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=Genetic+encoding+of+bicyclononynes+and+trans-cyclooctenes+for+site-specific+protein+labeling+in+vitro+and+in+live+mammalian+cells+via+rapid+fluorogenic+Diels-Alder+reactions.">Genetic encoding of bicyclononynes and trans-cyclooctenes for site-specific protein labeling in vitro and in live mammalian cells via rapid fluorogenic Diels-Alder reactions.</a> J. Am. Chem. Soc. 134 (25), 10317-10320 (2012).</li><li>Jewett, J. C., Sletten, E. M., Bertozzi, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+Cu-free+click+chemistry+with+readily+synthesized+biarylazacyclooctynones.">Rapid Cu-free click chemistry with readily synthesized biarylazacyclooctynones.</a> J. Am. Chem. Soc. 132 (11), 3688-3690 (2010).</li><li>Debets, M. F., 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=Azadibenzocyclooctynes+for+fast+and+efficient+enzyme+PEGylation+via+copper-free+(3+++2)+cycloaddition.">Azadibenzocyclooctynes for fast and efficient enzyme PEGylation via copper-free (3 + 2) cycloaddition.</a> Chem. Commun. 46 (1), 97-99 (2010).</li><li>Sletten, E. M., Bertozzi, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+mechanism+to+mouse:+a+tale+of+two+bioorthogonal+reactions.">From mechanism to mouse: a tale of two bioorthogonal reactions.</a> Acc. Chem. Res. 44 (9), 666-676 (2011).</li><li>Debets, M. F., 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=Bioconjugation+with+strained+alkenes+and+alkynes.">Bioconjugation with strained alkenes and alkynes.</a> Acc. Chem. Res. 44 (9), 805-815 (2011).</li><li>Mbua, N. E., Guo, J., Wolfert, M. A., Steet, R., Boons, G. -. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strain-promoted+alkyne&#8722;azide+cycloadditions+(SPAAC)+reveal+new+features+of+glycoconjugate+biosynthesis.">Strain-promoted alkyne&#8722;azide cycloadditions (SPAAC) reveal new features of glycoconjugate biosynthesis.</a> ChemBioChem. 12 (12), 1912-1921 (2011).</li><li>Kuzmin, A., Poloukhtine, A., Wolfert, M. A., Popik, V. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+functionalization+using+catalyst-free+azide-alkyne+cycloaddition.">Surface functionalization using catalyst-free azide-alkyne cycloaddition.</a> Bioconjug. Chem. 21 (11), 2076-2085 (2011).</li><li>Yao, J. Z., 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=Fluorophore+targeting+to+cellular+proteins+via+enzymemediated+azide+ligation+and+strain-promoted+cycloaddition.">Fluorophore targeting to cellular proteins via enzymemediated azide ligation and strain-promoted cycloaddition.</a> J. Am. Chem. Soc. 134 (8), 3720-3728 (2012).</li><li>Hao, Z., Hong, S., Chen, X., Chen, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Introducing+bioorthogonal+functionalities+into+proteins+in+living+cells.">Introducing bioorthogonal functionalities into proteins in living cells.</a> Acc. Chem. Res. 44 (9), 742-751 (2011).</li><li>Reddington, S. C., Tippmann, E. M., Jones, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Residue+choice+defines+efficiency+and+influence+of+bioorthogonal+protein+modification+via+genetically+encoded+strain+promoted+Click+chemistry.">Residue choice defines efficiency and influence of bioorthogonal protein modification via genetically encoded strain promoted Click chemistry.</a> Chem. Commun. 48 (9), 8419-8421 (2012).</li><li>Chari, R. V. J., Miller, M. L., Widdison, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antibody-drug+conjugates:+an+emerging+concept+in+cancer+therapy.">Antibody-drug conjugates: an emerging concept in cancer therapy.</a> Angew. Chem. Int. Ed. 53 (15), 3751-4005 (2014).</li><li>Tsao, M., Tian, F., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+staudinger+modification+of+proteins+containing+p-Azidophenylalanine.">Selective staudinger modification of proteins containing p-Azidophenylalanine.</a> ChemBioChem. 6 (12), 2147-2149 (2005).</li><li>Brustad, E. M., Lemke, E. A., Schultz, P. G., Deniz, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+general+and+efficient+method+for+the+site-specific+dual-labeling+of+proteins+for+single+molecule+fluorescence+resonance+energy+transfer.">A general and efficient method for the site-specific dual-labeling of proteins for single molecule fluorescence resonance energy transfer.</a> J. Am. Chem. Soc. 130 (52), 17664-17665 (2008).</li><li>Milles, 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=Click+strategies+for+single-molecule+protein+fluorescence.">Click strategies for single-molecule protein fluorescence.</a> J. Am. Chem. Soc. 134 (11), 5187-5195 (2012).</li><li>Jang, S., Sachin, K., Lee, h. J., Kim, D. W., Lee, h. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+simple+method+for+protein+conjugation+by+copper-free+click+reaction+and+its+application+to+antibody-free+Western+blot+analysis.">Development of a simple method for protein conjugation by copper-free click reaction and its application to antibody-free Western blot analysis.</a> Bioconjug. Chem. 23 (11), 2256-2261 (2012).</li><li>Kazane, S. A., 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=Self-assembled+antibody+multimers+through+peptide+nucleic+acid+conjugation.">Self-assembled antibody multimers through peptide nucleic acid conjugation.</a> J. Am. Chem. Soc. 135 (1), 340-346 (2012).</li><li>Ko, W., 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=Efficient+and+site-specific+antibody+labeling+by+strain-promoted+azide-alkyne+cycloaddition.">Efficient and site-specific antibody labeling by strain-promoted azide-alkyne cycloaddition.</a> Bull. Korean Chem. Soc. 36 (9), 2352-2354 (2015).</li><li>Young, T. S., Ahmad, I., Yin, J. A., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+enhanced+system+for+unnatural+amino+acid+mutagenesis+in+E.+coli.">An enhanced system for unnatural amino acid mutagenesis in E. coli.</a> J. Mol. Biol. 395 (2), 361-374 (2010).</li><li>Bradford, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+and+sensitive+method+for+the+quantitation+of+microgram+quantities+of+protein+utilizing+the+principle+of+protein-dye+binding.">A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.</a> Anal. Biochem. 72, 248-254 (1976).</li><li>Cho, H. 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=Structure+of+the+extracellular+region+of+HER2+alone+and+in+complex+with+the+Herceptin+Fab.">Structure of the extracellular region of HER2 alone and in complex with the Herceptin Fab.</a> Nature. 421 (6924), 756-760 (2003).</li><li>Kolb, H. C., Finn, M. G., Sharpless, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Click+chemistry+:+Diverse+chemical+function+from+a+few+good+reactions.">Click chemistry : Diverse chemical function from a few good reactions.</a> Angew. Chem. Int. Ed. 40 (11), 2004-2021 (2001).</li></ol>

The genetic incorporation of unnatural amino acids into proteins has several advantages over other methods used for protein modification. 1-3 One of the important advantages is its general applicability to any kind of protein. In principle, there is no limitation in selecting a target protein and a target site of the protein. However, replacement of a structurally or functionally important residue with a UAA may result in altering the structure and function of the target protein. Generally, residues that are e...

Since the genetic incorporation of p-methoxyphenylalanine in Escherichia coli was reported,1 more than 100 unnatural amino acids (UAAs) have been successfully incorporated into various proteins.1-3 Among these UAAs, the amino acids containing bioorthogonal functional groups have been extensively studied and represent the largest proportion. The bioorthogonal functional groups used in the UAAs include ketone,4 azide,5 alkyne,6 cyclooctyne,7 tetrazine,8 &#945;,&#946;-unsaturated amide,9 norbonene,10 transcyclooctene,11 and bicyclo[6.1.0]-nonyne.11 Although each functional group has its advantages and disadvantages, the azide-containing amino acids have been most extensively used for protein conjugation. p-Azidophenylalanine (AF), one of the azido-containing amino acids, is readily available, and its incorporation efficiency is excellent. Mutant proteins containing this amino acid can be reacted with alkynes by copper-catalyzed cycloaddition or with cyclooctynes by SPAAC.12-20
Recently, biopharmaceuticals have been attracting great attention in the pharmaceutical industry. The antibody-drug conjugate (ADC) is a class of therapeutic antibodies that are advantageous due to their ability for targeted therapy for the treatment of human cancers21 and other diseases. More than 50 ADCs are currently in clinical trials, and the number is rapidly increasing. In development of ADCs, many factors need to be considered to maximize the efficacy and minimize the side effects. Among these factors, an efficient and site-specific conjugation reaction to form a covalent bond between an antibody and a drug is critical. The desired efficiency and specificity in the conjugation reaction can be achieved by conjugation with a bioorthogonal functional group in an unnatural amino acid that is specifically incorporated into an antibody.22-26 Here, we report a protocol to site-specifically incorporate AF into an antibody fragment and conjugate the mutant antibody fragment with a biochemical probe.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1. plasmid Construction</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>plasmid pBAD_HerFab_L177TAG</td>
			<td></td>
			<td></td>
			<td>optionally contain the amber stop codon(TAG) at a desired position. Ko, W. et al. Efficient and Site-Specific Antibody Labeling by Strain-promoted Azide-Alkyne Cycloaddition. BKCS. 36 (9), 2352-2354, doi: 10.1002/bkcs.10423, (2015)</td>
		</tr>
		<tr>
			<td>plasmid pEvol-AFRS</td>
			<td></td>
			<td></td>
			<td>Young, T. S., Ahmad, I., Yin, J. A., and Schultz, P. G. An enhanced system for unnatural amino acid mutagenesis in E. coli. J. Mol. Biol. 395 (2), 361-374, doi: 10.1016/j.jmb.2009.10.030, (2010)</td>
		</tr>
		<tr>
			<td>DH10B</td>
			<td>Invitrogen</td>
			<td>C6400-03</td>
			<td>Expression Host</td>
		</tr>
		<tr>
			<td>Plasmid Mini-prep kit</td>
			<td>Nucleogen</td>
			<td>5112</td>
			<td>200/pack</td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Intron biotechnology</td>
			<td>32034</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>Ethidium bromide</td>
			<td>Alfa Aesar</td>
			<td>L07482</td>
			<td>1g</td>
		</tr>
		<tr>
			<td>LB Broth</td>
			<td>BD Difco</td>
			<td>244620</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>2. Culture preparation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2.1) Electroporation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro pulser&#160;</td>
			<td>BIO-RAD</td>
			<td>165-2100</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro pulser cuvette</td>
			<td>BIO-RAD</td>
			<td>165-2089</td>
			<td>0.1cm electrode gap, pkg. of 50</td>
		</tr>
		<tr>
			<td>Ampicillin Sodium</td>
			<td>Wako</td>
			<td>018-10372</td>
			<td>25g</td>
		</tr>
		<tr>
			<td>Chloramphenicol</td>
			<td>Alfa Aesar</td>
			<td>B20841</td>
			<td>25g</td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>SAMCHUN</td>
			<td>214230</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>SOC medium</td>
			<td>Sigma</td>
			<td>S1797</td>
			<td>100ML</td>
		</tr>
		<tr>
			<td>3. Expression and purification of HerFab-L177AF</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3.1 Expression of Herfab-L177AF</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>p-azido-L-phenylalanine (AF)</td>
			<td>Bachem</td>
			<td>F-3075.0001</td>
			<td>1g</td>
		</tr>
		<tr>
			<td>L(+)-Arabinose, 99%</td>
			<td>Acros</td>
			<td>104981000</td>
			<td>100g</td>
		</tr>
		<tr>
			<td>Hydrochloric acid, 35~37%</td>
			<td>SAMCHUN</td>
			<td>H0256</td>
			<td>500ml</td>
		</tr>
		<tr>
			<td>3.2 Cell lysis</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tris(hydroxymethyl)aminomethane, 99%</td>
			<td>SAMCHUN</td>
			<td>T1351</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>EDTA disodium salt dihydrate, 99.5%</td>
			<td>SAMCHUN</td>
			<td>E0064</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma</td>
			<td>S9378</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>Lysozyme</td>
			<td>Siyaku</td>
			<td>126-0671</td>
			<td>1g</td>
		</tr>
		<tr>
			<td>3.3 Ni-NTA Affinity Chromatography</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ni-NTA resin</td>
			<td>QIAGEN</td>
			<td>30210</td>
			<td>25ml</td>
		</tr>
		<tr>
			<td>Polypropylene column</td>
			<td>QIAGEN</td>
			<td>34924</td>
			<td>50/pack, 1ml capacity</td>
		</tr>
		<tr>
			<td>Imidazole, 99%</td>
			<td>SAMCHUN</td>
			<td>I0578</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>Sodium phosphate monobasic, 98%</td>
			<td>SAMCHUN</td>
			<td>S0919</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>Sodium Chloride, 99%</td>
			<td>SAMCHUN</td>
			<td>S2907</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>4. Conjugation of Purified HerFab-L177AF with Alkyne Probes Using Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC)&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cy5.5-ADIBO&#160;</td>
			<td>FutureChem</td>
			<td>FC-6119</td>
			<td>1mg</td>
		</tr>
		<tr>
			<td>5. Purification of Labeled HerFab</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Amicon Ultra 0.5 mL Centrifugal Filters</td>
			<td>MILLIPORE</td>
			<td>UFC500396</td>
			<td>96/pack, 500ul capacity</td>
		</tr>
		<tr>
			<td>6. SDS-PAGE Analysis of Labeled HerFab and Fluorescent Gel Scanning</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1,4-Dithio-DL-threitol, DTT, 99.5 %</td>
			<td>Sigma</td>
			<td>10708984001</td>
			<td>10g</td>
		</tr>
		<tr>
			<td>NuPAGE LDS Sample Buffer, 4X</td>
			<td>Thermofisher</td>
			<td>NP0007</td>
			<td>10ml</td>
		</tr>
		<tr>
			<td>MES running buffer</td>
			<td>Thermofisher</td>
			<td>NP0002</td>
			<td>500ml</td>
		</tr>
		<tr>
			<td>Nupage Novex 4-12% SDS PAGE gels</td>
			<td>Thermofisher</td>
			<td>NO0321</td>
			<td>12well</td>
		</tr>
		<tr>
			<td>Coomassie Brilliant Blue R-250</td>
			<td>Wako</td>
			<td>031-17922</td>
			<td>25g</td>
		</tr>
		<tr>
			<td>Typhoon 9210 variable mode imager</td>
			<td>Amersham Biosciences</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

efficient and site-specific antibody labeling by strain-promoted azide-alkyne cycloaddition

There are currently many chemical tools available to introduce chemical probes into proteins to study their structure and function. A useful method is protein conjugation by genetically introducing an unnatural amino acid containing a bioorthogonal functional group. This report describes a detailed protocol for site-specific antibody conjugation. The protocol includes experimental details for the genetic incorporation of an azide-containing amino acid, and the conjugation reaction by strain-promoted azide-alkyne cycloaddition (SPAAC). This strain-promoted reaction proceeds by simple mixing of the reacting molecules at physiological pH and temperature, and does not require additional reagents such as copper(I) ions and copper-chelating ligands. Therefore, this method would be useful for general protein conjugation and development of antibody drug conjugates (ADCs).

In this study, an antibody fragment was site-specifically conjugated with a fluorophore by incorporating an azide-containing amino acid into the fragment and reacting the mutant antibody fragment with a strained cyclooctyne (Figure 1). HerFab was selected as the target antibody fragment into which AF was incorporated as an azide-containing amino acid. To choose the residue in HerFab for the replacement with AF, the X-ray crystal structure of HerFab was analyzed. 30 <...

Watch this Scientific Journal Video about Efficient and Site-specific Antibody Labeling by Strain-promoted Azide-alkyne Cycloaddition at JoVE.com

Efficient and Site-specific Antibody Labeling by Strain-promoted Azide-alkyne Cycloaddition

Here, we present a protocol to site-specifically introduce chemical probes into an antibody fragment by genetically incorporating an azide-containing amino acid, and subsequently coupling the azide with a chemical probe by strain-promoted azide-alkyne cycloaddition (SPAAC).

There are currently many chemical tools available to introduce chemical probes into proteins to study their structure and function. A useful method is ...

The overall goal of this procedure is to site-specifically introduce chemical probes into an antibody fragment by genetically incorporating an azide-containing amino acid. This method can help answer key questions in the chemical biology field such as in protein modification, engineering and conjugation. The main advantage of this technique is that your target probe or broth can be site-specifically introduced into proteins or antibodies by simple mixing.After constructing the plasmids, add one microliter of each to 20 microliters of E.Coli strain DH10-beta at a concentration of two times 10 to the eight cells per microliter to a 1.5 milliliter centrifuge tube. Use a pipette to gently mix the solution. Then place 20 microliters of the mixed solution into a clean cuvette.Set the electroporation machine to 25 microfarads and 2.5 kilovolts. Then insert the cuvette into the slide of the shocking chamber. Push the slide into the chamber until the cuvette makes firm contact with the chamber electrodes.Press the pulse button once until the electroporation machine beeps. After this, add one milliliter SOC medium to the cuvette quickly. Then transfer the mixture to a test tube.Incubate with shaking at 37 degrees Celsius for one hour. After incubation is complete, spread the transformed E.Coli cells onto lysogeny broth agar plates containing appropriate antibiotics. Incubate the plates at 37 degrees Celsius for 12 hours.After the plate incubation is complete, inoculate a single transformed colony in five milliliters of LB medium containing antibiotics. Incubate with shaking for 12 hours at 37 degrees Celsius. Then transfer the primary culture into 200 milliliters of LB medium with 100 micrograms per milliliter ampicillin and one millimolar AF.Incubate with shaking at 37 degrees Celsius for at least three hours.Add two milliliters of 1.6 molar arabinose when the culture reaches an optical density of 0.8 at 550 nanometers. Then incubate with shaking at 30 degrees Celsius for 12 hours. When the incubation is complete, harvest the cells by centrifugation at 11, 000 times g for five minutes.Discard the supernatant and freeze the pellet at negative 20 degrees Celsius. When ready to lyse the cells, re-suspend the pellet in 20 milliliters of paraplasmic lysis buffer in a fresh centrifuge tube. Incubate the mixture at 37 degrees Celsius for one hour.Next, centrifuge the cell lysate at 18, 000 times g for 15 minutes at four degrees Celsius. Transfer the supernatant to a fresh tube and discard the pellet. Then add 400 microliters of an Ni-NTA resin suspension.Using a rotator, gently agitate the tube for one hour at four degrees Celsius. After mixing is complete, pour the suspension into a polypropylene column. Wash the resin three times with five milliliters of wash buffer.Elute the target antibody with 300 microliters of elution buffer. After this, determine the concentration of the mutant protein as outlined in the text protocol. Begin by adding 10 microliters of a 10 micromolar solution of HerFab-L177AF in phosphate buffer containing 10 millimolar sodium phosphate dibasic and 100 millimolar sodium chloride to a fresh centrifuge tube.Then add 20 microliters of a 200 micromolar solution of Cy 5.5 azadibenzocyclooctyne in water. After this, cover the reaction vessel with aluminum foil. Allow the stain-promoted cyclo-edition reaction to proceed for six hours at 37 degrees Celsius.Once the reaction is complete, add 30 microliters of sample and 450 microliters of phosphate buffer to wash free Cy 5.5 dye in a centrifugal filter spin column. Centrifuge the spin column at 14, 000 times g for 15 minutes at four degrees Celsius. Discard the flow-through and then transfer the purified sample to a 1.5 milliliter microcentrifuge tube.Store the purified labeled HerFab at four degrees Celsius unless ready for analysis. Begin by adding 13 microliters of 7.8 micromolar purified HerFab to a fresh tube. Then add five microliters of LDS protein sample buffer.Incubate the mixture at 95 degrees Celsius for 10 minutes. After incubation, attach the four to 12%Bis-Tris SDS-PAGE gel cassette to the electrophoresis cell. Add running buffer.Next, load the conjugated protein samples in the pre-stained molecular weight maker. Perform gel electrophoresis for 35 minutes at 200 volts. After the electrophoresis is complete, transfer the gel to a gel documentation and analysis system.Scan for Cy 5.5 and then stain the gel with a commercial protein stain. In this study, the antibody fragment Her-Fab is site-specifically conjugated with a This is accomplished by incorporating an azide-containing amino acid into the fragment and then reacting the mutant antibody fragment with a strained cyclooctyne. SDS-PAGE analysis is performed for mutant proteins expressed both with and without the azide-containing amino acid.As can be seen, the full-length antibody fragment was obtained only in the presence of the amino acid. The antibody containing the amino acid is evaluated for conjugation via reaction with a Cy 5.5 linked azadibenzocyclooctyne derivative Cy 5.5 and analyzed by SDS-PAGE. The fluorescence images show conjugation of the mutant antibody fragment with Cy 5.5 while no conjugation was observed in the control.Once properly expressed and purify your protein with acetylphenylalanine, the protein can be efficiently labeled with a probe with the strain Because the labeling reaction requires no additional reagent, you can introduce the probe into your target protein by simply mixing the probe with your protein. After watching this video, you should have a good understanding of how to site-specifically introduce chemical probe into an antibody fragment by genetically incorporating an azide-containing amino acid.

efficient-site-specific-antibody-labeling-strain-promoted-azide

Research

JoVE Journal

Biochemistry

Identification of Small Molecule-binding Proteins in a Native Cellular Environment by Live-cell Photoaffinity Labeling

Identifying the molecular target(s) of small molecules is a challenging but necessary step towards understanding their mechanism of action. While several target identification methods have been developed and used to successfully elucidate the binding proteins of a variety of small molecules, these techniques have drawbacks that make them unsuitable for detecting certain types of small molecule-target interactions. In particular, non-covalent interactions that depend on native cellular conditions, such as those of membrane proteins whose structures may be perturbed upon cell lysis, are often not amenable to affinity-based target identification methods. Here, we demonstrate a method wherein a probe containing a photolabile group is used to covalently crosslink to the small molecule binding protein within the environment of the live cell, allowing the detection and isolation of the target protein without the need for maintenance of the interaction after cell lysis. This technique is a valuable tool for studying biologically interesting small molecules with unknown mechanisms, both in the context of basic biology as well as drug discovery.

We describe here a method for identification of small molecule-binding proteins using photoaffinity labeling. The advantage of this technique is that binding and covalent labeling of the target proteins occurs within the live cellular environment, removing the risk of disrupting native protein structure and binding conditions upon cell lysis.

Identifying the molecular target(s) of small molecules is a challenging but necessary step towards understanding their mechanism of action. While several ...

Bacterial Inner-membrane Display for Screening a Library of Antibody Fragments

Antibodies engineered for intracellular function must not only have affinity for their target antigen, but must also be soluble and correctly folded in the cytoplasm. Commonly used methods for the display and screening of recombinant antibody libraries do not incorporate intracellular protein folding quality control, and, thus, the antigen-binding capability and cytoplasmic folding and solubility of antibodies engineered using these methods often must be engineered separately. Here, we describe a protocol to screen a recombinant library of single-chain variable fragment (scFv) antibodies for antigen-binding and proper cytoplasmic folding simultaneously. The method harnesses the intrinsic intracellular folding quality control mechanism of the Escherichia coli twin-arginine translocation (Tat) pathway to display an scFv library on the E. coli inner membrane. The Tat pathway ensures that only soluble, well-folded proteins are transported out of the cytoplasm and displayed on the inner membrane, thereby eliminating poorly folded scFvs prior to interrogation for antigen-binding. Following removal of the outer membrane, the scFvs displayed on the inner membrane are panned against a target antigen immobilized on magnetic beads to isolate scFvs that bind to the target antigen. An enzyme-linked immunosorbent assay (ELISA)-based secondary screen is used to identify the most promising scFvs for additional characterization. Antigen-binding and cytoplasmic solubility can be improved with subsequent rounds of mutagenesis and screening to engineer antibodies with high affinity and high cytoplasmic solubility for intracellular applications.

We provide a method to simultaneously screen a library of antibody fragments for binding affinity and cytoplasmic solubility by using the Escherichia coli twin-arginine translocation pathway, which has an inherent quality control mechanism for intracellular protein folding, to display the antibody fragments on the inner membrane.

Antibodies engineered for intracellular function must not only have affinity for their target antigen, but must also be soluble and correctly folded in ...

Laboratory Scale Production and Purification of a Therapeutic Antibody

Ensuring the successful production of a therapeutic antibody begins early on in the development process. The first stage is vector expression of the antibody genes followed by stable transfection into a suitable cell line. The stable clones are subjected to screening in order to select those clones with desired production and growth characteristics. This is a critical albeit time-consuming step in the process. This protocol considers vector selection and sourcing of antibody sequences for the expression of a therapeutic antibody. The methods describe preparation of vector DNA for stable transfection of a suspension variant of human embryonic kidney 293 (HEK-293) cell line, using polyethylenimine (PEI). The cells are transfected as adherent cells in serum-containing media to maximize transfection efficiency, and afterwards adapted to serum-free conditions. Large scale production, setup as batch overgrow cultures is used to yield antibody protein that is purified by affinity chromatography using an automated fast protein liquid chromatography (FPLC) instrument. The antibody yields produced by this method can provide sufficient protein to begin initial characterization of the antibody. This may include in vitro assay development or physicochemical characterization to aid in the time-consuming task of clonal screening for lead candidates. This method can be transferable to the development of an expression system for the production of biosimilar antibodies.

This protocol describes the production of a therapeutic antibody in a mammalian expression system. The methods described include preparation of vector DNA, stable transfection and serum-free adaptation of a human embryonic kidney 293 cell line, set up of large scale cultures and purification using affinity chromatography.

Ensuring the successful production of a therapeutic antibody begins early on in the development process. The first stage is vector expression of the ...

Enhanced Sample Multiplexing of Tissues Using Combined Precursor Isotopic Labeling and Isobaric Tagging (cPILOT)

There is an increasing demand to analyze many biological samples for disease understanding and biomarker discovery. Quantitative proteomics strategies that allow simultaneous measurement of multiple samples have become widespread and greatly reduce experimental costs and times. Our laboratory developed a technique called combined precursor isotopic labeling and isobaric tagging (cPILOT), which enhances sample multiplexing of traditional isotopic labeling or isobaric tagging approaches. Global cPILOT can be applied to samples originating from cells, tissues, bodily fluids, or whole organisms and gives information on relative protein abundances across different sample conditions. cPILOT works by 1) using low pH buffer conditions to selectively dimethylate peptide N-termini and 2) using high pH buffer conditions to label primary amines of lysine residues with commercially-available isobaric reagents (see Table of Materials/Reagents). The degree of sample multiplexing available is dependent on the number of precursor labels used and the isobaric tagging reagent. Here, we present a 12-plex analysis using light and heavy dimethylation combined with six-plex isobaric reagents to analyze 12 samples from mouse tissues in a single analysis. Enhanced multiplexing is helpful for reducing experimental time and cost and more importantly, allowing comparison across many sample conditions (biological replicates, disease stage, drug treatments, genotypes, or longitudinal time-points) with less experimental bias and error. In this work, the global cPILOT approach is used to analyze brain, heart, and liver tissues across biological replicates from an Alzheimer&#39;s disease mouse model and wild-type controls. Global cPILOT can be applied to study other biological processes and adapted to increase sample multiplexing to greater than 20 samples.

Enhanced Sample Multiplexing of Tissues Using Combined Precursor Isotopic Labeling and Isobaric Tagging cPILOT

Combined precursor isotopic labeling and isobaric tagging (cPILOT) is a quantitative proteomics strategy that enhances sample multiplexing capabilities of isobaric tags. This protocol describes the application of cPILOT to tissues from an Alzheimer's disease mouse model and wild-type controls.

There is an increasing demand to analyze many biological samples for disease understanding and biomarker discovery. Quantitative proteomics strategies ...

Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the use of four routinely used biosensor platforms in our laboratory to evaluate the binding affinity and kinetics of ten high-affinity monoclonal antibodies (mAbs) against human proprotein convertase subtilisin kexin type 9 (PCSK9). While both Biacore T100 and ProteOn XPR36 are derived from the well-established Surface Plasmon Resonance (SPR) technology, the former has four flow cells connected by serial flow configuration, whereas the latter presents 36 reaction spots in parallel through an improvised 6 x 6 crisscross microfluidic channel configuration. The IBIS MX96 also operates based on the SPR sensor technology, with an additional imaging feature that provides detection in spatial orientation. This detection technique coupled with the Continuous Flow Microspotter (CFM) expands the throughput significantly by enabling multiplex array printing and detection of 96 reaction sports simultaneously. In contrast, the Octet RED384 is based on the BioLayer Interferometry (BLI) optical principle, with fiber-optic probes acting as the biosensor to detect interference pattern changes upon binding interactions at the tip surface. Unlike the SPR-based platforms, the BLI system does not rely on continuous flow fluidics; instead, the sensor tips collect readings while they are immersed in analyte solutions of a 384-well microplate during orbital agitation.
Each of these biosensor platforms has its own advantages and disadvantages. To provide a direct comparison of these instruments&#39; ability to provide quality kinetic data, the described protocols illustrate experiments that use the same assay format and the same high-quality reagents to characterize antibody-antigen kinetics that fit the simple 1:1 molecular interaction model.

We describe here protocols for the measurement of antibody-antigen binding affinity and kinetics using four commonly used biosensor platforms.

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the ...

Analysis of Histone Antibody Specificity with Peptide Microarrays

Post-translational modifications (PTMs) on histone proteins are widely studied for their roles in regulating chromatin structure and gene expression. The mass production and distribution of antibodies specific to histone PTMs has greatly facilitated research on these marks. As histone PTM antibodies are key reagents for many chromatin biochemistry applications, rigorous analysis of antibody specificity is necessary for accurate data interpretation and continued progress in the field. This protocol describes an integrated pipeline for the design, fabrication and use of peptide microarrays for profiling the specificity of histone antibodies. The design and analysis aspects of this procedure are facilitated by ArrayNinja, an open-source and interactive software package we recently developed to streamline the customization of microarray print formats. This pipeline has been used to screen a large number of commercially available and widely used histone PTM antibodies, and data generated from these experiments are freely available through an online and expanding Histone Antibody Specificity Database. Beyond histones, the general methodology described herein can be applied broadly to the analysis of PTM-specific antibodies.

This manuscript describes methods for applying peptide microarray technology to specificity profiling of antibodies that recognize histones and their post-translational modifications.

Post-translational modifications (PTMs) on histone proteins are widely studied for their roles in regulating chromatin structure and gene expression. The ...

Deep Proteome Profiling by Isobaric Labeling, Extensive Liquid Chromatography, Mass Spectrometry, and Software-assisted Quantification

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) coupled to tandem mass spectrometry (LC-MS/MS) and isobaric labeling multiplexing capacity. Here, we introduce a deep-proteomics profiling protocol that combines 10-plex tandem mass tag (TMT) labeling with an extensive LC/LC-MS/MS platform, and post-MS computational interference correction to accurately quantitate whole proteomes. This protocol includes the following main steps: protein extraction and digestion, TMT labeling, 2-dimensional (2D) LC, high-resolution mass spectrometry, and computational data processing. Quality control steps are included for troubleshooting and evaluating experimental variation. More than 10,000 proteins in mammalian samples can be confidently quantitated with this protocol. This protocol can also be applied to the quantitation of post translational modifications with minor changes. This multiplexed, robust method provides a powerful tool for proteomic analysis in a variety of complex samples, including cell culture, animal tissues, and human clinical specimens.

We present a protocol to accurately quantitate proteins with isobaric labelling, extensive fractionation, bioinformatics tools, and quality control steps in combination with liquid chromatography interfaced to a high-resolution mass spectrometer.

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) ...

Method for Efficient Refolding and Purification of Chemoreceptor Ligand Binding Domain

Identification of natural ligands of chemoreceptors and structural studies aimed at elucidation of the molecular basis of the ligand specificity can be greatly facilitated by the production of milligram amounts of pure, folded ligand binding domains. Attempts to heterologously express periplasmic ligand binding domains of bacterial chemoreceptors in Escherichia coli (E. coli) often result in their targeting into inclusion bodies. Here, a method is presented for protein recovery from inclusion bodies, its refolding and purification, using the periplasmic dCACHE ligand binding domain of Campylobacter jejuni (C. jejuni) chemoreceptor Tlp3 as an example. The approach involves expression of the protein of interest with a cleavable His6-tag, isolation and urea-mediated solubilisation of inclusion bodies, protein refolding by urea depletion, and purification by means of affinity chromatography, followed by tag removal and size-exclusion chromatography. The circular dichroism spectroscopy is used to confirm the folded state of the pure protein. It has been demonstrated that this protocol is generally useful for production of milligram amounts of dCACHE periplasmic ligand binding domains of other bacterial chemoreceptors in a soluble and crystallisable form.

A procedure is presented for the refolding of the dCACHE periplasmic ligand binding domain of Campylobacter jejuni chemoreceptor Tlp3 from inclusion bodies and the purification to yield milligram quantities of protein.

Identification of natural ligands of chemoreceptors and structural studies aimed at elucidation of the molecular basis of the ligand specificity can be ...

Isolation of Glomeruli and In Vivo Labeling of Glomerular Cell Surface Proteins

Proteinuria results from the disruption of the glomerular filter that is composed of the fenestrated endothelium, glomerular basement membrane, and podocytes with their slit diaphragms. The delicate structure of the glomerular filter, especially the slit diaphragm, relies on the interplay of diverse cell surface proteins. Studying these cell surface proteins has so far been limited to in vitro studies or histologic analysis. Here, we present a murine in vivo biotinylation labeling method, which enables the study of glomerular cell surface proteins under physiologic and pathophysiologic conditions. This protocol contains information on how to perfuse mouse kidneys, isolate glomeruli, and perform endogenous immunoprecipitation of a protein of interest. Semi-quantitation of glomerular cell surface abundance is readily available with this novel method, and all proteins accessible to biotin perfusion and immunoprecipitation can be studied. In addition, isolation of glomeruli with or without biotinylation enables further analysis of glomerular RNA and protein as well as primary glomerular cell culture (i.e., primary podocyte cell culture).

Isolation of Glomeruli and In Vivo Labeling of Glomerular Cell Surface Proteins

Here we present a protocol for murine in vivo labeling of glomerular cell surface proteins with biotin. This protocol contains information on how to perfuse mouse kidneys, isolate glomeruli, and perform endogenous immunoprecipitation of the protein of interest.

Proteinuria results from the disruption of the glomerular filter that is composed of the fenestrated endothelium, glomerular basement membrane, and ...

Proteome-wide Quantification of Labeling Homogeneity at the Single Molecule Level

Cell proteomes are often characterized using electrophoresis assays, where all species of proteins in the cells are non-specifically labeled with a fluorescent dye and are spotted by a photodetector following their separation. Single molecule fluorescence imaging can provide ultrasensitive protein detection with its ability for visualizing individual fluorescent molecules. However, the application of this powerful imaging method to electrophoresis assays is hampered by the lack of ways to characterize the homogeneity of fluorescent labeling of each protein species across the proteome. Here, we developed a method to evaluate the labeling homogeneity across the proteome based on a single molecule fluorescence imaging assay. In our measurement using a HeLa cell sample, the proportion of proteins labeled with at least one dye, which we termed &#8216;labeling occupancy&#8217; (LO), was determined to range from 50% to 90%, supporting the high potential of the application of single molecule imaging to sensitive and precise proteome analysis.

Here, we present a protocol to assess the labeling homogeneity for each protein species in a complex protein sample at the single molecule level.

Cell proteomes are often characterized using electrophoresis assays, where all species of proteins in the cells are non-specifically labeled with a ...