1DQJ

CRYSTAL STRUCTURE OF THE ANTI-LYSOZYME ANTIBODY HYHEL-63 COMPLEXED WITH HEN EGG WHITE LYSOZYME

Summary for 1DQJ

• Entry DOI: 10.2210/pdb1dqj/pdb
• Related: 1DQQ 1dqm
• Descriptor: ANTI-LYSOZYME ANTIBODY HYHEL-63 (LIGHT CHAIN), ANTI-LYSOZYME ANTIBODY HYHEL-63 (HEAVY CHAIN), LYSOZYME, ... (4 entities in total)
• Functional Keywords: antibody, protein-protein complex, hen egg white lysozyme, immune system-hydrolase complex, immune system/hydrolase
• Biological source: Mus musculus (house mouse); More
• Cellular location: Secreted: P00698
• Total number of polymer chains: 3
• Total formula weight: 60471.05

Authors

Li, H.,Mariuzza, R.A. (deposition date: 2000-01-04, release date: 2000-01-19, Last modification date: 2024-11-06)

Primary citation

Li, Y.,Li, H.,Smith-Gill, S.J.,Mariuzza, R.A.
Three-dimensional structures of the free and antigen-bound Fab from monoclonal antilysozyme antibody HyHEL-63(,).
Biochemistry, 39:6296-6309, 2000

PubMed Abstract: Antigen-antibody complexes provide useful models for studying the structure and energetics of protein-protein interactions. We report the cloning, bacterial expression, and crystallization of the antigen-binding fragment (Fab) of the anti-hen egg white lysozyme (HEL) antibody HyHEL-63 in both free and antigen-bound forms. The three-dimensional structure of Fab HyHEL-63 complexed with HEL was determined to 2.0 A resolution, while the structure of the unbound antibody was determined in two crystal forms, to 1.8 and 2.1 A resolution. In the complex, 19 HyHEL-63 residues from all six complementarity-determining regions (CDRs) of the antibody contact 21 HEL residues from three discontinuous polypeptide segments of the antigen. The interface also includes 11 bound water molecules, 3 of which are completely buried in the complex. Comparison of the structures of free and bound Fab HyHEL-63 reveals that several of the ordered water molecules in the free antibody-combining site are retained and that additional waters are added upon complex formation. The interface waters serve to increase shape and chemical complementarity by filling cavities between the interacting surfaces and by contributing to the hydrogen bonding network linking the antigen and antibody. Complementarity is further enhanced by small (<3 A) movements in the polypeptide backbones of certain antibody CDR loops, by rearrangements of side chains in the interface, and by a slight shift in the relative orientation of the V(L) and V(H) domains. The combining site residues of complexed Fab HyHEL-63 exhibit reduced temperature factors compared with those of the free Fab, suggesting a loss in conformational entropy upon binding. To probe the relative contribution of individual antigen residues to complex stabilization, single alanine substitutions were introduced in the epitope of HEL recognized by HyHEL-63, and their effects on antibody affinity were measured using surface plasmon resonance. In agreement with the crystal structure, HEL residues at the center of the interface that are buried in the complex contribute most to the binding energetics (DeltaG(mutant) - DeltaG(wild type) > 3.0 kcal/mol), whereas the apparent contributions of solvent-accessible residues at the periphery are much less pronounced (<1.5 kcal/mol). In the latter case, the mutations may be partially compensated by local rearrangements in solvent structure that help preserve shape complementarity and the interface hydrogen bonding network.

PubMed: 10828942
DOI: 10.1021/bi000054l

Experimental method

X-RAY DIFFRACTION (2 Å)