Sequential electron transfer in the primary photosynthetic reaction of Rhodobacter sphaeroides

The primary photochemistry in the photosynthesis of bacteriochlorophyll containing organisms i s a light-induced charge separation within a protein complex ca l l e d reaction center (RC). Recently, the c r y s t a l structures of the reaction centers could be determined for the f i r s t time /1,2/. For Rhodopseudomonas (Rps.) v i r i d i s and Rhodobacter (Hb*) sphaeroides the structure analysis gave very s i m i l a r arrangements of the prosthetic groups /3/. They are disposed as two branches (A, B ) in an approximate C-2 symmetry* Two bacteriochlorophyll molecules from the so-called special pair (P) located on the symmetry axis. Starting at the s p e c i a l pair each branch consists of an accessory bacteriochlorophyll {Β Λ , B B ) , a . bacteriopheophytin (H A , H B ) , and a quinone ( O A , Q B ) .