The structure and function of the cytochrome c2: reaction center electron transfer complex from Rhodobacter sphaeroides

摘要: In the photosynthetic bacterium, Rhodobacter sphaeroides, mobile electron carrier, cytochrome c2 (cyt c2) transfers an from reduced heme to photooxidized bacteriochlorophyll dimer in membrane bound reaction center (RC) as part of light induced cyclic transfer chain. A complex between these two proteins that is active has been crystallized and its structure determined by X-ray diffraction. The cyt:RC shows cyt positioned at periplasmic surface RC. exposed edge close tunneling contact with acceptor through intervening bridging residue, Tyr L162 located on RC directly above dimer. binding interface can be divided into regions: a short-range interaction domain long-range domain. includes residues immediately surrounding region around display intermolecular contacts optimized for transfer. These include small number hydrophobic interactions, hydrogen bonds pi-cation interaction. consists solvated complementary charged residues; positively negatively provide long range electrostatic interactions steer position rapid association.