title: Selectivity in rhodopsin-phospholipid interactions.
abstract: This series of experiments systematically evaluated the effect of phospholipid headgroup structure on the interaction between rhodopsin and phospholipids. Two types of experiments were reported. First, ESR experiments involving spin-labeled phosphatidylserine, phosphatidic acid, and phosphatidylcholine demonstrated that, in the fluid-isotropic phase of dimyristoylphosphatidylcholine (DMPC)-rhodopsin membranes, the relative order of rhodopsin-induced immobilization was phosphatidic acid greater than phosphatidylcholine greater than phosphatidylserine. Second, the effect of rhodopsin incorporation on the dimyristoylphosphatidylserine (DMPS) gel to liquid-crystalline phase transition was analyzed with ESR techniques. A partial, binary phase diagram for the DMPS-rhodopsin system at pH 7.0 was constructed by studying the partitioning of Tempo between polar and hydrophobic domains as a function of temperature and system composition. A main result of this analysis was the finding that rhodopsin broadens and reduces the amplitude of the DMPS phase transition to a much smaller extent than it does the DMPC phase transition. When interpreted in terms of theoretical treatments of integral protein-lipid interactions, this indicates that rhodopsin has a lower affinity for DMPS than DMPC.
mesh_terms: D000818:Animals; D002417:Cattle; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D008027:Light; D008560:Membrane Fluidity; D010712:Phosphatidic Acids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D012168:Retinal Pigments / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism* / Q000528:radiation effects; D013113:Spin Labels; D013329:Structure-Activity Relationship
chemical_list: D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D010743:Phospholipids; D012168:Retinal Pigments; D013113:Spin Labels; C042859:dimyristoylphosphatidylserine; D012243:Rhodopsin; D004134:Dimyristoylphosphatidylcholine