What controls the rates of interprotein electron-transfer reactions

Rates of electron-transfer (ET) reactions are dependent on driving force, r eorganizational energy, distance, and the nature of the medium which the el ectron must traverse. In kinetically complex biological systems, non-ET rea ctions may be required to activate the system for ET and may also influence the observed rates. Studies of ET from tryptophan tryptophylquinone to cop per to heme in the methylamine dehydrogenase-amicyanin-cytochrome c-551i ET complex, as well as studies of other physiologic redox protein complexes, are used to illustrate the combination of factors which control rates of in terprotein ET reactions.