9222741 Kostic The objective of this research is to understand the mechanism of electron transfer in electrostatic (noncovalent) protein/protein complexes. The molecular basis for the optimal reaction rate and specificity will be studied with the fully-characterized metalloproteins cytochrome c (cyt) and plastocyanin (pc). Building upon this laboratory's recent successes, a detailed plan is proposed that combines molecular biology (mutation of pc), computational chemistry (analysis of electron-transfer paths), and kinetics (laser flash photolysis) in order to achieve the following: (1) determine reactive orientations of cyt/pc complexes; (2) pinpoint dominant transfer paths from the heme to the Cu site; (3) examine how variations in distant electronic couplings controls the rate of electron transfer; (4) determine the rate of structural rearrangement of cyt/pc complexes and establish kinetic requirements for "gating"; and (5) explore the importance for electron transfer of conformational fluctuations at the protein/protein interface. %%% This research is important because electron-transfer reactions of metalloproteins are essential to various biological processes. These reactions are involved in animal metabolism and plant photosynthesis. A deeper understanding of electron transfer, at the molecular level, is necessary for a better understanding of the origin and transformations of chemical energy in a living cell. ***
