1L7I

Crystal Structure of the anti-ErbB2 Fab2C4

DOI: 10.2210/pdb1L7I/pdb

Classification: IMMUNE SYSTEM
Organism(s): Homo sapiens
Expression System: Escherichia coli
Mutation(s): No

Deposited: 2002-03-15 Released: 2002-07-10
Deposition Author(s): Vajdos, F.F., Adams, C.W., Breece, T.N., Presta, L.G., de Vos, A.M., Sidhu, S.S.

Experimental Data Snapshot

Method: X-RAY DIFFRACTION
Resolution: 1.80 Å
R-Value Free: 0.230
R-Value Work: 0.197

wwPDB Validation 3D Report Full Report

This is version 1.2 of the entry. See complete history.

Literature

Comprehensive functional maps of the antigen-binding site of an anti-ErbB2 antibody obtained with shotgun scanning mutagenesis.

Vajdos, F.F., Adams, C.W., Breece, T.N., Presta, L.G., de Vos, A.M., Sidhu, S.S.

(2002) J Mol Biol 320: 415-428

PubMed: 12079396 Search on PubMed
DOI: 10.1016/S0022-2836(02)00264-4
Primary Citation of Related Structures:
1L7I

PubMed Abstract:

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.

Organizational Affiliation:

Department of Protein Engineering, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.

Macromolecules

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(by identity cutoff) | 3D Structure

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
chimera of Fab2C4: "humanized" murine monoclonal antibody	A [auth L]	214	Homo sapiens	Mutation(s): 0
UniProt
Find proteins for Q7Z3Y4 (Homo sapiens) Explore Q7Z3Y4 Go to UniProtKB: Q7Z3Y4
Protein Feature View Expand
Reference Sequence

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(by identity cutoff) | 3D Structure

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
chimera of Fab2C4: "humanized" murine monoclonal antibody	B [auth H]	222	Homo sapiens	Mutation(s): 0
Protein Feature View Expand
Reference Sequence

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram	3D Interactions
SO4 Query on SO4 Download Ideal Coordinates CCD File SDF format, chain C [auth L] SDF format, chain D [auth L] MOL2 format, chain C [auth L] MOL2 format, chain D [auth L]	C [auth L], D [auth L]	SULFATE ION O₄ S QAOWNCQODCNURD-UHFFFAOYSA-L		Ligand Interaction