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.
Tsukatani
Yusuke
Y
Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan.
Azai
Chihiro
C
Kondo
Toru
T
Itoh
Shigeru
S
Oh-Oka
Hirozo
H
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