Beta-gamma subunit interaction is required for catalysis by H(+)-ATPase (ATP synthase). Beta subunit amino acid replacements suppress a gamma subunit mutation having a long unrelated carboxyl terminus.
The mechanisms of energy coupling and catalytic co-operativity are not yet understood for H(+)-ATPase (ATP synthase). An Escherichia coli gamma subunit frameshift mutant (downstream of Thr-gamma 277) could not grow by oxidative phosphorylation because both mechanisms were defective (Iwamoto, A., Miki, J., Maeda, M., and Futai, M. (1990) J. Biol. Chem. 265, 5043-5048). The defect(s) of the gamma frameshift was obvious, because the mutant subunit had a carboxyl terminus comprising 16 residues different from those in the wild type. However, in this study, we surprisingly found that an Arg-beta 52-->Cys or Gly-beta 150-->Asp replacement could suppress the deleterious effects of the gamma frameshift. The membranes of the two mutants (gamma frameshift/Cys-beta 52 with or without a third mutation, Val-beta 77-->Ala) exhibited increased oxidative phosphorylation, together with 70-100% of the wild type ATPase activity. Similarly, the gamma frameshift/Asp-beta 150 mutant could grow by oxidative phosphorylation, although this mutant had low membrane ATPase activity. These results suggest that the beta subunit mutation suppressed the defects of catalytic cooperativity and/or energy coupling in the gamma mutant, consistent with the notion that conformational transmission between the two subunits is pertinent for this enzyme.
Jeanteur-De Beukelaer
C
C
Division of Biological Science, Osaka University, Japan.
Omote
H
H
Iwamoto-Kihara
A
A
Maeda
M
M
Futai
M
M
D000595:Amino Acid Sequence; D001120:Arginine; D001224:Aspartic Acid; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine; D017931:DNA Primers; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D016368:Frameshift Mutation; D005998:Glycine; D007700:Kinetics; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009876:Operon; D010085:Oxidative Phosphorylation; D010957:Plasmids; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D017433:Protein Structure, Secondary; D006180:Proton-Translocating ATPases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping
D017931:DNA Primers; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D001224:Aspartic Acid; D001120:Arginine; D006180:Proton-Translocating ATPases; D003545:Cysteine; D005998:Glycine