ABSTRACT
Many electron transfer reactions occurring in vivo involve pairs of proteins in which at least one is free to diffuse. Small, electron-carrying proteins like cytochrome c, plastocyanin or ferredoxin allow the distribution of reducing power over large distances within the cell, and to a variety of metabolic acceptor systems. This chapter shows how theory and experiment can be used to develop a physical picture of the interaction between two redox proteins. A simple kinetic model for a bimolecular reaction is described to provide a framework for the subsequent discussion. The chapter discusses the formation of the complex by diffusion and the role of long-range electrostatic forces, the specific binding forces and energies that may be involved in bringing the proteins in close apposition for rapid electron transfer, and the structure of the reaction complex and the degree to which it may be static or dynamic in character. Some possible alternative binding strategies are also suggested.
