ABSTRACT
Detailed structural analysis of electron transfer complexes can provide information about both complex formation and electron transfer. There are several categories of biological electron transfer proteins which vary in their structure and catalytic complexity. The simplest are the one-domain one-electron-carrier proteins in which the electron resides transiently on a special cofactor such as a metal atom or a haem. This chapter presents a brief introduction to members of two of the most common types of electron carriers, cytochromes and cupredoxins. It considers two-site proteins containing pairs of redox cofactors bound either to a single domain, such as ascorbate oxidase or to separate domains such as the flavocytchromes. Two systems of weakly associating protein complexes, the methylamine dehydrogenase-amicyanin-cytochrome system and the cytochrome c peroxidase-cytochrome c system are described. These sections are followed by discussions of the structures and dynamics of the complexes in solution and the enzymatic and electron transfer activities of the crystalline complexes.
