PMID:15159387

Citation	Grabar, TB and Cain, BD (2004) Genetic complementation between mutant b subunits in F1F0 ATP synthase. J. Biol. Chem. 279:31205-11
Abstract	In Escherichia coli, a parallel homodimer of identical b subunits constitutes the peripheral stalk of F(1)F(0) ATP synthase. Although the two b subunits have long been viewed as a single functional unit, the asymmetric nature of the enzyme complex suggested that the functional roles of each b subunit should not necessarily be considered equivalent. Previous mutagenesis studies of the peripheral stalk suffered from the fact that mutations in the uncF(b) gene affected both of the b subunits. We developed a system to express and study F(1)F(0) ATP synthase complexes containing two different b subunits. Two mutations already known to inactivate the F(1)F(0) ATP synthase complex have been studied using this experimental system. An evolutionarily conserved arginine, b(Arg-36), was known to be crucial for F(1)F(0) ATP synthase function, and the last four C-terminal amino acids had been shown to be important for enzyme assembly. Experiments expressing one of the mutants with a wild type b subunit demonstrated the presence of heterodimers in F(1)F(0) ATP synthase complexes. Activity assays suggested that the heterodimeric F(1)F(0) complexes were functional. When the two defective b subunits were expressed together and in the absence of any wild type b subunit, an active F(1)F(0) ATP synthase complex was assembled. This mutual complementation between fully defective b subunits indicated that each of the two b subunits makes a unique contribution to the functions of the peripheral stalk, such that one mutant b subunit is making up for what the other is lacking.
Links	PubMed Online version:10.1074/jbc.M404420200
Keywords	Bacterial Proton-Translocating ATPases/chemistry; Bacterial Proton-Translocating ATPases/genetics; Bacterial Proton-Translocating ATPases/metabolism; Dimerization; Escherichia coli/enzymology; Escherichia coli/genetics; Escherichia coli/growth & development; Genes, Bacterial; Genetic Complementation Test; Models, Molecular; Mutagenesis; Mutation; Protein Structure, Quaternary; Protein Subunits; Recombinant Proteins/chemistry; Recombinant Proteins/genetics; Recombinant Proteins/metabolism
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