Two molecules of cytochrome c function as the electron donors to P840 in the reaction center complex isolated from a green sulfur bacterium, Chlorobium tepidum

[摘要]

A photoactive reaction center complex was isolated from a thermophilic green sulfur bacterium, Chlorobium tepidum under anaerobic conditions. The electron transfer occurred from heme c to the photo-oxidized reaction center chlorophyll, P840⁺, with a half time () of 110 or 340 μs at 24 or 12°C, respectively. Optical measurements under multiflash excitations indicated that two hemes function as the immediate electron donors to P840⁺. SDS-PAGE analysis of the RC complex in combination with the N-terminal amino acid sequence analyses revealed five subunit bands; a core protein (65 kDa), the light harvesting bacteriochlorophyll a protein (41 kDa), a protein with 2[4Fe-4S] clusters (31 kDa), monoheme cytochrome c (22 kDa), and a 18-kDa protein whose function is unknown. The reaction center complex, thus, contains two molecules of cytochrome c per P840.

[学科分类] 生物化学/生物物理

[关键词] Cytochrome c;Electron transfer;Green sulfur bacteria;Photosynthesis;Reaction center;Iron-sulfur center;BChl;bacteriochlorophyll;RC;reaction center;PS;photosystem;P840;primary electron donor;PMSF;phenylmethanesulfonyl fluoride;Cys;cysteine;DTT;dithiothreitol;SDS-PAGE;SDS-polyacrylamide gel electrophoresis;N-;amino-;TMBZ;3;3′;5;5′-tetramethylbenzidine;PscA and PscB;core and iron-sulfur proteins encoded by pscA and pscB genes respectively in Chlorobium