Electron flow through metalloproteins

Abstract

Understanding the underlying physics and chem. of biol. electron transfer processes is the goal of much of the work in my lab. Employing laser flash-quench triggering methods, my coworkers and I have shown that long-range (1.5 to 2.5 nm) electron tunneling reactions in Ru-modified cytochromes and blue copper proteins occur on microsecond to nanosecond timescales. Redox equiv. can be transferred even longer distances by multistep tunneling (called hopping) through intervening tyrosines and tryptophans: notably, in our work on cytochrome P 450 and azurin, we have found that long-range hole hopping through intervening tryptophans can be orders of magnitude faster than single-step tunneling. Could hole hopping through Tyr/Trp chains protect redox enzymes from oxidative damage. Jay Winkler and I think so: by examg. the structures of P450s and many other oxygenases, we have identified conserved Tyr/Trp chains that could transfer holes rapidly from uncoupled high-potential intermediates to reductants in contact with protein surface sites.