title: Organization in the membrane of the N-terminal proton-translocating domain of the beta subunit of the pyridine nucleotide transhydrogenase of Escherichia coli.
abstract: The proton-translocating transmembrane pyridine nucleotide transhydrogenase of Escherichia coli is composed of two types of subunits, alpha and beta. The beta subunit has several membrane-spanning segments in the N-terminal region followed by a cytosolic C-terminal domain bearing a binding site for NADP(H). The N-terminal region contains at least one residue involved in the process of transmembrane proton translocation. Using site-directed mutagenesis cysteine residues were introduced at selected sites into the N-terminal region of the beta subunit. The pattern of labelling of these residues with 3-(N-maleimidyl propionyl)biocytin and other sulfhydryl reagents has shown that a model in which the N-terminal region of the beta subunit spans the membrane in eight segments is more likely than a previously proposed six segment model (Holmberg et al. (1994) Biochemistry 33, 7691-7700). The preferred model accounts for the site of labelling of a glutamate residue (Glu124) in the N-terminal domain by N,N-dicyclohexylcarbodiimide.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada.
authors.forename: N A
authors.initials: NA
authors.lastname: Glavas
authors.forename: C
authors.initials: C
authors.lastname: Hou
authors.forename: P D
authors.initials: PD
authors.lastname: Bragg
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002462:Cell Membrane / Q000201:enzymology; D003545:Cysteine / Q000737:chemistry; D004926:Escherichia coli / Q000201:enzymology*; D017136:Ion Transport; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009249:NADP / Q000378:metabolism; D009250:NADP Transhydrogenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011522:Protons; D013439:Sulfhydryl Reagents
chemical_list: D011522:Protons; D013439:Sulfhydryl Reagents; D009249:NADP; D009250:NADP Transhydrogenases; D003545:Cysteine