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Type 1 Reaction Center of Photosynthetic Heliobacteria †
Author(s) -
Ohoka Hirozo
Publication year - 2007
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/2006-03-29-ir-860
Subject(s) - photosynthetic reaction centre , quinone , chemistry , electron transfer , cytochrome c , purple bacteria , moiety , cytochrome b6f complex , photochemistry , electron acceptor , cytochrome , photosystem i , electron transport chain , molecule , crystallography , p700 , heme , stereochemistry , photosystem ii , photosynthesis , biochemistry , organic chemistry , mitochondrion , enzyme
The reaction center (RC) of heliobacteria contains iron–sulfur centers as terminal electron acceptors, analogous to those of green sulfur bacteria as well as photosystem I in cyanobacteria and higher plants. Therefore, they all belong to the so‐called type 1 RCs, in contrast to the type 2 RCs of purple bacteria and photosystem II containing quinone molecules. Although the architecture of the heliobacterial RC as a protein complex is still unknown, it forms a homodimer made up of two identical PshA core proteins, where two symmetrical electron transfer pathways along the C2 axis are assumed to be equally functional. Electrons are considered to be transferred from membrane‐bound cytochrome c (PetJ) to a special pair P800, a chlorophyll a ‐like molecule A 0 , (a quinone molecule A 1 ) and a [4Fe–4S] center F X and, finally, to 2[4Fe–4S] centers F A /F B . No definite evidence has been obtained for the presence of functional quinone acceptor A 1 . An additional interesting point is that the electron transfer reaction from cytochrome c to P800 proceeds in a collisional mode. It is highly dependent on the temperature, ion strength and/or viscosity in a reaction medium, suggesting that a heme‐binding moiety fluctuates in an aqueous phase with its amino‐terminus anchored to membranes.