title: Correlation between active form and dimeric structure of mitochondrial nicotinamide nucleotide transhydrogenase from beef heart.
abstract: The active form of purified mitochondrial nicotinamide nucleotide transhydrogenase from beef heart was investigated by crosslinking with dimethylsuberimidate and SDS-PAGE, with or without pretreatment with the inactivating detergent Triton X-100. In the absence of detergent, crosslinked isomers of the dimeric form of 208-235 kDa were obtained. Addition of detergent led to the simultaneous loss of the dimers and the bulk of the activity. Removal of the detergent led to a partial restoration of both activity and the dimeric forms. The results suggest that the active form is a dimer, and that the detergent-dependent conversion to the largely inactive monomer is reversible. It is proposed that the mechanism of inactivation of transhydrogenase by Triton X-100 involves a disruption of essential hydrophobic interactions between the membrane-spanning regions of the monomers.
authors.affiliation: Department of Molecular Biology, University of Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Ormö
authors.forename: B
authors.initials: B
authors.lastname: Persson
authors.forename: J
authors.initials: J
authors.lastname: Rydström
mesh_terms: D000818:Animals; D002417:Cattle; D004120:Dimethyl Suberimidate / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D009250:NADP Transhydrogenases / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D004120:Dimethyl Suberimidate; D009250:NADP Transhydrogenases