Fluorescent probe study of temperature-induced conformational changes in cytochrome oxidase in lecithin vesicle and solubilized systems.
A protein-bound label, N-(1-anilinonaphthyl-4)-maleimide (ANM), was used to investigate conformational changes in bovine heart cytochrome oxidase. The fluidity of cytochrome oxidase vesicles was monitored by a lipophilic probe, 1,6-diphenyl-1,3,5-hexatriene. The fluroescence intensity and emission anisotropy of these probes were examined between 4 and 60 degrees C in enzyme--dipalmitoyllecithin vesicles, in enzyme--dimyristoyllecithin vesicles, in enzyme--dioleoyllecithin vesicles, and in the soluble enzyme. The temperature-dependent changes in these quantities indicated that there were two types of conformational changes in oxidized cytochrome oxidase: one was attributed to an intrinsic enzyme conformation change which occurred around 20 degrees C, and the other was attributed to a conformational change induced by the lipid phase transition. Although ANM-reactive subunits of cytochrome oxidase in these four lecithin vesicle and solubilized systems were different from each other, subunit I always reacted with ANM in preference to other subunits.
D000818:Animals; D002417:Cattle; D004161:Diphenylhexatriene; D003576:Electron Transport Complex IV; D008301:Maleimides; D008433:Mathematics; D009206:Myocardium / Q000201:enzymology; D009281:Naphthalenes; D010713:Phosphatidylcholines; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013696:Temperature
D008301:Maleimides; D009281:Naphthalenes; D010713:Phosphatidylcholines; D004161:Diphenylhexatriene; C010854:N-(1-anilinonaphthalyl)-4-maleimide; D003576:Electron Transport Complex IV