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| | {{STRUCTURE_1a2y| PDB=1a2y | SCENE= }} | | {{STRUCTURE_1a2y| PDB=1a2y | SCENE= }} |
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| - | '''HEN EGG WHITE LYSOZYME, D18A MUTANT, IN COMPLEX WITH MOUSE MONOCLONAL ANTIBODY D1.3'''
| + | ===HEN EGG WHITE LYSOZYME, D18A MUTANT, IN COMPLEX WITH MOUSE MONOCLONAL ANTIBODY D1.3=== |
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| - | ==Overview==
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| - | Alanine scanning mutagenesis, double mutant cycles, and X-ray crystallography were used to characterize the interface between the anti-hen egg white lysozyme (HEL) antibody D1.3 and HEL. Twelve out of the 13 nonglycine contact residues on HEL, as determined by the high-resolution crystal structure of the D1.3-HEL complex, were individually truncated to alanine. Only four positions showed a DeltaDeltaG (DeltaGmutant - DeltaGwild-type) of greater than 1.0 kcal/mol, with HEL residue Gln121 proving the most critical for binding (DeltaDeltaG = 2.9 kcal/mol). These residues form a contiguous patch at the periphery of the epitope recognized by D1.3. To understand how potentially disruptive mutations in the antigen are accommodated in the D1.3-HEL interface, we determined the crystal structure to 1.5 A resolution of the complex between D1.3 and HEL mutant Asp18 --> Ala. This mutation results in a DeltaDeltaG of only 0.3 kcal/mol, despite the loss of a hydrogen bond and seven van der Waals contacts to the Asp18 side chain. The crystal structure reveals that three additional water molecules are stably incorporated in the antigen-antibody interface at the site of the mutation. These waters help fill the cavity created by the mutation and form part of a rearranged solvent network linking the two proteins. To further dissect the energetics of specific interactions in the D1.3-HEL interface, double mutant cycles were carried out to measure the coupling of 14 amino acid pairs, 10 of which are in direct contact in the crystal structure. The highest coupling energies, 2.7 and 2.0 kcal/mol, were measured between HEL residue Gln121 and D1.3 residues VLTrp92 and VLTyr32, respectively. The interaction between Gln121 and VLTrp92 consists of three van der Waals contacts, while the interaction of Gln121 with VLTyr32 is mediated by a hydrogen bond. Surprisingly, however, most cycles between interface residues in direct contact in the crystal structure showed no significant coupling. In particular, a number of hydrogen-bonded residue pairs were found to make no net contribution to complex stabilization. We attribute these results to accessibility of the mutation sites to water, such that the mutated residues exchange their interaction with each other to interact with water. This implies that the strength of the protein-protein hydrogen bonds in these particular cases is comparable to that of the protein-water hydrogen bonds they replace. Thus, the simple fact that two residues are in direct contact in a protein-protein interface cannot be taken as evidence that there necessarily exists a productive interaction between them. Rather, the majority of such contacts may be energetically neutral, as in the D1.3-HEL complex.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_9609690}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 9609690 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_9609690}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Immunoglobulin v region]] | | [[Category: Immunoglobulin v region]] |
| | [[Category: Signal]] | | [[Category: Signal]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 09:43:45 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 15:53:17 2008'' |
Revision as of 12:53, 30 June 2008
Template:STRUCTURE 1a2y
HEN EGG WHITE LYSOZYME, D18A MUTANT, IN COMPLEX WITH MOUSE MONOCLONAL ANTIBODY D1.3
Template:ABSTRACT PUBMED 9609690
About this Structure
1A2Y is a Protein complex structure of sequences from Gallus gallus and Mus musculus. Full crystallographic information is available from OCA.
Reference
A mutational analysis of binding interactions in an antigen-antibody protein-protein complex., Dall'Acqua W, Goldman ER, Lin W, Teng C, Tsuchiya D, Li H, Ysern X, Braden BC, Li Y, Smith-Gill SJ, Mariuzza RA, Biochemistry. 1998 Jun 2;37(22):7981-91. PMID:9609690
Page seeded by OCA on Mon Jun 30 15:53:17 2008
