Abstract
The crystal structure for an antibody-antigen system, that of the anti-hen egg lysozyme monoclonal antibody HyHEL-5 complexed to lysozyme, is used as the starting point for computer simulations of diffusional encounters between the two proteins. The investigation consists of two parts: first, the linearized Poisson-Boltzmann equation is solved to determine the long-range electrostatic forces between antibody and antigen, and then, the relative motion as influenced by these forces is modeled within Brownian motion theory. The effects of various point mutations on the calculated reaction rate are considered. It is found that charged residues close to the binding site exert the greatest influence in steering the proteins into a configuration favorable for their binding, while more distant mutations are qualitatively described by the Smoluchowski model for the mutual diffusion of two uniformly charged spheres. The antibody residues involved in forming salt links with the lysozyme, Glu-H35 and Glu-H50, appear to be particularly important in electrostatic steering, as neutralization of both of them yields reaction rates that are two to three orders of magnitude below those of wild-type rates. The relative rates obtained from the simulations can be tested through kinetic measurements on mutant protein complexes. Kinetically efficient partners can also be designed and constructed through directed mutagenesis.
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Selected References
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- Allison S. A., Bacquet R. J., McCammon J. A. Simulation of the diffusion-controlled reaction between superoxide and superoxide dismutase. II. Detailed models. Biopolymers. 1988 Feb;27(2):251–269. doi: 10.1002/bip.360270207. [DOI] [PubMed] [Google Scholar]
- Davies D. R., Padlan E. A., Sheriff S. Antibody-antigen complexes. Annu Rev Biochem. 1990;59:439–473. doi: 10.1146/annurev.bi.59.070190.002255. [DOI] [PubMed] [Google Scholar]
- Getzoff E. D., Cabelli D. E., Fisher C. L., Parge H. E., Viezzoli M. S., Banci L., Hallewell R. A. Faster superoxide dismutase mutants designed by enhancing electrostatic guidance. Nature. 1992 Jul 23;358(6384):347–351. doi: 10.1038/358347a0. [DOI] [PubMed] [Google Scholar]
- Gilson M. K., Honig B. H. Calculation of electrostatic potentials in an enzyme active site. Nature. 1987 Nov 5;330(6143):84–86. doi: 10.1038/330084a0. [DOI] [PubMed] [Google Scholar]
- Northrup S. H., Boles J. O., Reynolds J. C. Brownian dynamics of cytochrome c and cytochrome c peroxidase association. Science. 1988 Jul 1;241(4861):67–70. doi: 10.1126/science.2838904. [DOI] [PubMed] [Google Scholar]
- Northrup S. H., Erickson H. P. Kinetics of protein-protein association explained by Brownian dynamics computer simulation. Proc Natl Acad Sci U S A. 1992 Apr 15;89(8):3338–3342. doi: 10.1073/pnas.89.8.3338. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Raman C. S., Jemmerson R., Nall B. T., Allen M. J. Diffusion-limited rates for monoclonal antibody binding to cytochrome c. Biochemistry. 1992 Oct 27;31(42):10370–10379. doi: 10.1021/bi00157a027. [DOI] [PubMed] [Google Scholar]
- Sines J. J., Allison S. A., McCammon J. A. Point charge distributions and electrostatic steering in enzyme/substrate encounter: Brownian dynamics of modified copper/zinc superoxide dismutases. Biochemistry. 1990 Oct 9;29(40):9403–9412. doi: 10.1021/bi00492a014. [DOI] [PubMed] [Google Scholar]
- Smith-Gill S. J., Wilson A. C., Potter M., Prager E. M., Feldmann R. J., Mainhart C. R. Mapping the antigenic epitope for a monoclonal antibody against lysozyme. J Immunol. 1982 Jan;128(1):314–322. [PubMed] [Google Scholar]