title: Chemical labeling studies on bovine heart mitochondrial cytochrome c oxidase dispersed in nonionic detergents.
abstract: In order to investigate the structural interactions of nonionic detergents with bovine heart mitochondrial cytochrome c oxidase (COX), a series of hydrophilic chemical modification reagents were used to map regions on COX which are not shielded by dodecyl beta-D-maltoside (DM), Triton X-100 (TX-100), and Tween 80 (TW-80). Low levels of incorporation of the chemical reagents [35S]benzenediazoniumsulfonate (DABS) and N-succinimidyl [3H]propionate (SP) into COX dispersed in TW-80 indicate that the bulky headgroup and hydrophobic moiety of this detergent effectively shield the enzyme from the aqueous environment. Subunits II and Va/Vb [nomenclature of Merle, P., & Kadenbach, B. (1982) Eur. J. Biochem. 125, 239-244] show an increased reactivity to [35S]DABS and [3H]SP in TW-80 and may reflect an increased exposure of these subunits to the aqueous phase in comparison to COX dispersed in TX-100 or DM. More [35S]DABS is incorporated into COX in DM than TX-100-dispersed enzyme; DABS heavily labels subunits III, VIa, and VIb in DM. While COX in TX-100 is more reactive with [3H]SP than DM-dispersed enzyme, there is no difference in the distribution of label (either DABS or SP) within the subunits of COX in DM or TX-100. Increased surface exposure of COX in TX-100 is indicated by an enhanced sensitivity of COX electron-transfer activity in enzyme chemically modified by the cross-linking reagent N-succinimidyl 3-[(4-azidophenyl)dithio]propionate (SADP) in TX-100 as compared to enzyme chemically cross-linked in the other detergents.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biochemistry, School of Medicine, Wright State University, Dayton, Ohio 45435.
authors.forename: L A
authors.initials: LA
authors.lastname: Estey
authors.forename: A J
authors.initials: AJ
authors.lastname: Lincoln
authors.forename: L J
authors.initials: LJ
authors.lastname: Prochaska
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002850:Chromatography, Gel; D003902:Detergents / Q000494:pharmacology*; D003979:Diazonium Compounds / Q000378:metabolism; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000302:isolation & purification / Q000378:metabolism*; D005960:Glucosides / Q000494:pharmacology; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D011136:Polysorbates / Q000494:pharmacology; D011422:Propionates / Q000378:metabolism; D013425:Sulfanilic Acids / Q000378:metabolism
chemical_list: D003902:Detergents; D003979:Diazonium Compounds; D005960:Glucosides; D011136:Polysorbates; D011422:Propionates; D013425:Sulfanilic Acids; C021749:N-succinimidyl propionate; D011092:Polyethylene Glycols; C040358:dodecyl maltoside; D017830:Octoxynol; D003576:Electron Transport Complex IV; C000469:diazobenzenesulfonic acid