title: Apparent dependence of interactions between cytochrome b5 and cytochrome b5 reductase upon translational diffusion in dimyristoyl lecithin liposomes.
abstract: Dimyristoyl lecithin liposomes, containing cytochrome b5 reductase (NADH:ferricytochrome b5 oxidoreductase, EC 1.6.2.2) and varying amounts of cytochrome b5, were used to measure flavoprotein catalysis alone and catalysis requiring electron transfer between the reductase and cytochrome as a function of temperature. Whereas flavoprotein catalysis showed a simple linear temperature dependence in an Arrhenius plot, the reaction involving electron transfer between the two bound enzymes showed a marked, 4-fold, change in rate at the crystalline-liquid crystalline phase transition of the hydrocarbon chains of the lecithin vesicles and a second, minor change involving the minor transition. These data represent strong evidence that protein-protein interactions in this membrane model system are dependent upon translational diffusion of nonpolar segments of the proteins in the hydrocarbon region of the phospholipid bilayer.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002850:Chromatography, Gel; D003579:Cytochrome Reductases / Q000378:metabolism; D003580:Cytochromes / Q000378:metabolism; D004579:Electron Transport; D007700:Kinetics; D008081:Liposomes; D008099:Liver / Q000201:enzymology; D008297:Male; D008854:Microscopy, Electron; D009227:Myristic Acids; D010713:Phosphatidylcholines; D011485:Protein Binding; D013696:Temperature; D013816:Thermodynamics
chemical_list: D003580:Cytochromes; D008081:Liposomes; D009227:Myristic Acids; D010713:Phosphatidylcholines; D003579:Cytochrome Reductases