title: Assembly of multimeric proteins. Effect of mutations in the alpha-subunit on membrane assembly and activity of pyridine nucleotide transhydrogenase.
abstract: The pyridine nucleotide transhydrogenase of Escherichia coli is an inner membrane protein of two different subunits (alpha and beta). It functions as a proton pump. The highly hydrophilic carboxy-terminal tail of ten amino acid residues in the alpha-subunit determines the correct folding and proper assembly of the beta-subunit leading to a functional enzyme. Premature termination of the alpha-subunit six amino acid residues from the carboxy-terminal end abolishes the activity completely. Although the two subunits are still assembled into the membrane, the conformation of the beta-subunit is perturbed. Systematic truncation and site-directed substitutions revealed that at least one positive charge in the carboxy-terminal region is required for efficient assembly of the two subunits to give a functional enzyme, while a phenylalanine residue, essential for activity, has no apparent effect on the extent of assembly of the two subunits.
authors.affiliation: Department of Biochemistry, University of British Columbia, Vancouver, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Ahmad
authors.forename: N A
authors.initials: NA
authors.lastname: Glavas
authors.forename: P D
authors.initials: PD
authors.lastname: Bragg
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000201:enzymology; D010450:Endopeptidases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009250:NADP Transhydrogenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D046911:Macromolecular Substances; D008565:Membrane Proteins; D009250:NADP Transhydrogenases; D010450:Endopeptidases