Hydrophobic mismatch influencing the structure-function relationship of the reaction center from photosynthetic bacterium Rhodobacter sphaeroides

摘要: The photosynthetic organisms consist a cluster of membrane bound protein-pigment complexes, which utilize absorbed photons to drive electron transfer reactions convert light energy into chemical energy. In the bacterial reaction center from Rhodobacter sphaeroides , induces an primary donor, special pair two bacteriochorophylls forming dimer, through series intermediate acceptors and quinone Q A reversibly-bound B . Reaction centers have been reconstituted various liposomes, with varying fatty acid chain lengths C 12 18 resulting in different hydrophobic thicknesses lipid bilayer. Compensations are expected both protein if not matched. Lipid-protein interactions were explored identified due this mismatch by studying phase behavior probing function protein. optimal thickness for membrane, using saturated phospholipids incorporate center, was found be equivalent carbon length 14 Prolonged illumination induced conformational rearrangements structure. Lipid environment, acidic pH, long illumination, low temperature favored formation long-lived charge separated state. This light-adapted conformation had lifetime up 8.9 hours, is three million times as much dark-adapted state flash excitations.