Pigment Composition in the Reaction Center Complex from the Thermophilic Green Sulfur Bacterium, Chlorobium tepidum: Carotenoid Glucoside Esters, Menaquinone and Chlorophylls

Abstract

Distribution of pigments in the reaction center (RC) complex, chlorosomes and chlorosome-free membranes prepared from the green sulfur bacterium, Chlorobium tepidum, was analyzed. The RC complex contained approximately 40 molecules of bacteriochlor ophyll (BChl) a per P840, half of which are estimated to be in the Fenna-Matthews-Olson (FMO) protein. Carotenes (2 molecules per P840) occupied only one third of the total carotenoids. The remaining carotenoids (4 to 5 molecules per P840) were OH-chlorobactene glucoside ester and OH-/-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 component is chlorobactene, were found mainly in chlorosomes, and two kinds of carotenoid glucoside esters were observed in chlorosome-free membranes.