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| {{STRUCTURE_1l7i| PDB=1l7i | SCENE= }} | | {{STRUCTURE_1l7i| PDB=1l7i | SCENE= }} |
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| '''Crystal Structure of the anti-ErbB2 Fab2C4'''
| | ===Crystal Structure of the anti-ErbB2 Fab2C4=== |
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| ==Overview==
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| Shotgun scanning combinatorial mutagenesis was used to study the antigen-binding site of Fab2C4, a humanized monoclonal antibody fragment that binds to the extracellular domain of the human oncogene product ErbB2. Essentially all the residues in the Fab2C4 complementarity determining regions (CDRs) were alanine-scanned using phage-displayed libraries that preferentially allowed side-chains to vary as the wild-type or alanine. A separate homolog-scan was performed using libraries that allowed side-chains to vary only as the wild-type or a similar amino acid residue. Following binding selections to isolate functional clones, DNA sequencing was used to determine the wild-type/mutant ratios at each varied position, and these ratios were used to assess the contributions of each side-chain to antigen binding. The alanine-scan revealed that most of the side-chains that contribute to antigen binding are located in the heavy chain, and the Fab2C4 three-dimensional structure revealed that these residues fall into two groups. The first group consists of solvent-exposed residues which likely make energetically favorable contacts with the antigen and thus comprise the functional-binding epitope. The second group consists of buried residues with side-chains that pack against other CDR residues and apparently act as scaffolding to maintain the functional epitope in a binding-competent conformation. The homolog-scan involved subtle mutations, and as a result, only a subset of the side-chains that were intolerant to alanine substitutions were also intolerant to homologous substitutions. In particular, the 610 A2 functional epitope surface revealed by alanine-scanning shrunk to only 369 A2 when mapped with homologous substitutions, suggesting that this smaller subset of side-chains may be involved in more precise contacts with the antigen. The results validate shotgun scanning as a rapid and accurate method for determining the functional contributions of individual side-chains involved in protein-protein interactions.
| | The line below this paragraph, {{ABSTRACT_PUBMED_12079396}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 12079396 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_12079396}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Fab fragment]] | | [[Category: Fab fragment]] |
| [[Category: Ig domain]] | | [[Category: Ig domain]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 23:37:54 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jul 2 11:52:36 2008'' |
