Pigment composition in the reaction center complex from the thermophilic green sulfur bacterium, Chlorobium tepidum: Carotenoid glucoside esters, menaquinone and chlorophylls

Distribution of pigments in the reaction center (RC) complex, chlorosomes a cid chlorosome-free membranes prepared from the green sulfur bacterium, Chl orobium tepidum, was analyzed. The RC complex contained approximately 40 mo lecules of bacteriochlorophyll (BChl) a per P840, half of which are estimat ed to be in the Fenna-Matthews-Olson (FMO) protein. Carotenes (2 molecules per P840) occupied only one third of the total carotenoids. The remaining c arotenoids (4 to 5 molecules per P840) were OH-chlorobactene glucoside este r and OH-gamma-carotene glucoside ester. Dihydrochlorobactene was decreased compared with cellular carotenes. Furthermore, approximately 9 C670 and 1 menaquinone-7 per P840 were also found. BChl c and carotenes, whose major c omponent is chlorobactene, were found mainly in chlorosomes, and two kinds of carotenoid glucoside esters were observed in chlorosome-free membranes.