Continuum Electrostatic Model for the Binding of Cytochrome c2 to the Photosynthetic Reaction Center from Rhodobacter sphaeroides
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- 作者：Osamu Miyashita ; José ; N. Onuchic ; and Melvin Y. Okamura
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：October 14, 2003
- 年：2003
- 卷：42
- 期：40
- 页码：11651 - 11660
- 全文大小：245K
- 年卷期：v.42,no.40(October 14, 2003)
- ISSN：1520-4995
文摘
Electrostatic interactions are important for protein-protein association. In this study, weexamined the electrostatic interactions between two proteins, cytochrome c2 (cyt c2) and the reactioncenter (RC) from the photosynthetic bacterium Rhodobacter sphaeroides, that function in intermolecularelectron transfer in photosynthesis. Electrostatic contributions to the binding energy for the cyt c2-RCcomplex were calculated using continuum electrostatic methods based on the recent cocrystal structure[Axelrod, H. L., et al. (2002) J. Mol. Biol. 319, 501-515]. Calculated changes in binding energy due tomutations of charged interface residues agreed with experimental results for a protein dielectric constant
in of 10. However, the electrostatic contribution to the binding energy for the complex was close to zerodue to unfavorable desolvation energies that compensate for the favorable Coulomb attraction. Theelectrostatic energy calculated as a function of displacement of the cyt c2 from the bound position showeda shallow minimum at a position near but displaced from the cocrystal configuration. These results showthat although electrostatic steering is present, other short-range interactions must be present to contributeto the binding energy and to determine the structure of the complex. Calculations made to model theexperimental data on association rates indicate a solvent-separated transition state for binding in whichthe cyt c2 is displaced ~8 Å above its position in the bound complex. These results are consistent witha two-step model for protein association: electrostatic docking of the cyt c2 followed by desolvation toform short-range van der Waals contacts for rapid electron transfer.
in of 10. However, the electrostatic contribution to the binding energy for the complex was close to zerodue to unfavorable desolvation energies that compensate for the favorable Coulomb attraction. Theelectrostatic energy calculated as a function of displacement of the cyt c2 from the bound position showeda shallow minimum at a position near but displaced from the cocrystal configuration. These results showthat although electrostatic steering is present, other short-range interactions must be present to contributeto the binding energy and to determine the structure of the complex. Calculations made to model theexperimental data on association rates indicate a solvent-separated transition state for binding in whichthe cyt c2 is displaced ~8 Å above its position in the bound complex. These results are consistent witha two-step model for protein association: electrostatic docking of the cyt c2 followed by desolvation toform short-range van der Waals contacts for rapid electron transfer.