Parallel electron donation pathways to cytochrome c(z) in the type I homodimeric photosynthetic reaction center complex of Chlorobium tepidum.
We studied the regulation mechanism of electron donations from menaquinol:cytochrome c oxidoreductase and cytochrome c-554 to the type I homodimeric photosynthetic reaction center complex of the green sulfur bacterium Chlorobium tepidum. We measured flash-induced absorption changes of multiple cytochromes in the membranes prepared from a mutant devoid of cytochrome c-554 or in the reconstituted membranes by exogenously adding cytochrome c-555 purified from Chlorobium limicola. The results indicated that the photo-oxidized cytochrome c(z) bound to the reaction center was rereduced rapidly by cytochrome c-555 as well as by the menaquinol:cytochrome c oxidoreductase and that cytochrome c-555 did not function as a shuttle-like electron carrier between the menaquinol:cytochrome c oxidoreductase and cytochrome c(z). It was also shown that the rereduction rate of cytochrome c(z) by cytochrome c-555 was as high as that by the menaquinol:cytochrome c oxidoreductase. The two electron-transfer pathways linked to sulfur metabolisms seem to function independently to donate electrons to the reaction center.
Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan.
Yusuke
Y
Tsukatani
Chihiro
C
Azai
Toru
T
Kondo
Shigeru
S
Itoh
Hirozo
H
Oh-Oka
D000042:Absorption; D002462:Cell Membrane / Q000378:metabolism; D041883:Chlorobium / Q000378:metabolism*; D045303:Cytochromes b / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism*; D019281:Dimerization; D004583:Electrons; D008954:Models, Biological; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D013057:Spectrum Analysis; D013997:Time Factors
D045322:Photosynthetic Reaction Center Complex Proteins; D045304:Cytochromes c; D045303:Cytochromes b