Flavocytochrome c will be investigated further as a soluble model of oriented coupled electron transfer. The heme and flavin subunits are tightly associated and it has been shown that electron flow is from doner to flavin, followed by rapid intramolecular transfer to the heme and finally to the acceptor. The flavin and heme are optimally oriented for electron transfer and the electrons enter and exit via different paths. Flavocytrochrome c will be cloned and the mechanism of electron transfer will be further characterized. Considerable advances in our knowledge of biological electron transfer have been achieved, although many crucial questions remain unanswered. Much of our present understanding is based on studies with cytochrome c (the only soluble protein in the respiratory chain) and other small proteins having a single redox center. It is clear that redox potential, electrostatic and steric factors play an important role. In larger proteins containing multiple redox centers these interactions are less well understood, but additional factors play a role. Thus the mechanism of action of cytochrome c may not be representative as a whole. Flavocytchrome c presents an opportunity to investigate an electron transfer system which more directly mimics the less tractable membrane found electron carriers of respiratory and photosynthetic pathways.
