Direct and indirect electron transfer from cytochromes c and c2 to the photosynthetic reaction center in pigment-protein complexes isolated from Rhodocyclus gelatinosus

AbstractElectron transfer from soluble cytochromes c and c2 to the photo-oxidized bacteriochlorophyll dimer was studied in photosynthetic reaction center (RC) complexes and RC-B870 complexes isolated from Rhodocyclus gelatinosus. In the RC-B870 complex which consists of 6 polypeptides including a bound cytochrome subunit, cytochrome c from horse heart or cytochrome c2, from R. gelatinosus was oxidized by photo-oxidized bacteriochlorophyll dimer indirectly via cytochrome c-555 in the complex. In the RC complex which is composed of two polypeptides, the oxidized bacteriochlorophyll dimer was reduced directly by the soluble cytochromes. Although direct electron transfer from soluble cytochrome does not function in R. gelatinosus in vivo, it would replace indirect electron donation if the bound cytochrome were lost mutationally