ELECTRON-TRANSFER BETWEEN CYTOCHROME-C AND CYTOCHROME-C PEROXIDASE

The reaction between cytochrome c (CC) and cytochrome c peroxidase (Cc P) is a very attractive system for investigating the fundamental mecha nism of biological electron transfer. The resting ferric state of CcP is oxidized by hydrogen peroxide to compound I (CMPI) containing an ox yferryl heme and an indolyl radical cation on Trp-191. CMPI is sequent ially reduced to CMPII and then to the resting state CcP by two molecu les of CC. In this review we discuss the use of a new ruthenium photor eduction technique and other rapid kinetic techniques to address the f ollowing important questions: (1) What is the initial electron accepto r in CMPI? (2) What are the true rates of electron transfer from CC to the radical cation and to the oxyferryl heme? (3) What are the bindin g domains and pathways for electron transfer from CC to the radical ca tion and the oxyferryl heme? (4) What is the mechanism for the complet e reaction under physiological conditions?