Hopping in the Electron-Transfer Photocycle of the 1:1 Complex of Zn-Cytochrome c Peroxidase with Cytochrome c

摘要

The physiological electron-transfer(ET)partners,cytochrome c peroxidase(CcP)and cytochrome c(Cc),often are viewed as a paradigmatic protein-protein ET pair,but in fact form a quite complex system because CcP contains two redox centers,the heme and an adjacent tryptophan,W191.These protein partners nonetheless occupy a central role in the study of interprotein ET,in considerable part because the heme of either partner can be modified to exhibit photoinitiated ET through substitution of Zn(or Mg)for Fe.Laser excitation of the Zn-porphyrin(ZnP)to its triplet excited state(~3ZnP)initiates direct"heme-heme"ET to the ferriheme center across the protein-protein interface,with ET rate constant,KAPPA_F(eq 1)