The DMPC lipid phase transition influences differently the first and the second electron transfer reactions in bacterial reaction centers.
Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were incorporated in dimyristoylphosphatidylcholine (DMPC) liposomes. The first and second electron transfer rates (k(AB)(1) and k(AB)(2), respectively) between the first and the second quinone electron acceptors have been measured as a function of temperature, across the phase transition of DMPC (23 degrees C). The Eyring plots of k(AB)(1) display straight lines. In contrast, the Eyring plots for k(AB)(2) in proteoliposomes show a break at about 23.5 degrees C. This physical discrimination between the two electron transfer reactions demonstrates that the stiffness of the lipid environment of the RCs and/or the protein-protein interactions influence the parameters governing k(AB)(2), but not the gating process limiting k(AB)(1).
Taly
Antoine
A
Centre de Génétique Moléculaire, Bâtiment 24, CNRS, 91198 Gif-sur-Yvette, France.
Baciou
Laura
L
Sebban
Pierre
P
D020285:Cryoelectron Microscopy; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D004579:Electron Transport; D007700:Kinetics; D008560:Membrane Fluidity; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism* / Q000648:ultrastructure; D011510:Proteolipids / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D012242:Rhodobacter sphaeroides / Q000378:metabolism / Q000648:ultrastructure; D013696:Temperature
D045322:Photosynthetic Reaction Center Complex Proteins; D011510:Proteolipids; C020485:proteoliposomes; D004134:Dimyristoylphosphatidylcholine