title: Amino acid substitutions in the epsilon-subunit of the F1F0-ATPase of Escherichia coli.
abstract: A mutant strain of Escherichia coli was isolated in which Gly-48 of the mature epsilon-subunit of the energy-transducing adenosine triphosphatase was replaced by Asp. This amino acid substitution caused inhibition of ATPase activity (about 70%), loss of ATP-dependent proton translocation and lowered oxidative phosphorylation, but did not affect proton translocation through the F0. Purified F1-ATPase from the mutant strain bound to stripped membranes with the same affinity as the normal F1-ATPase. Partial revertant strains were isolated in which Pro-47 of the epsilon-subunit was replaced by Ser or Thr. Pro-47 and Gly-48 are predicted to be residues 2 and 3 in a Type II beta-turn and the Gly-48 to Asp substitution is predicted to cause a change from a Type II to a Type I or III beta-turn. Space-filling models of the beta-turn (residues 46-49) in the normal, mutant and partial revertant epsilon-subunits indicate that the peptide oxygen between Pro-47 and Gly-48 is in a different position to the peptide oxygen between Pro-47 and Asp-48 and that the substitution of Pro-47 by either Ser or Thr restores an oxygen close to the original position. It is suggested that the peptide oxygen between Pro-47 and Gly-48 of the epsilon-subunit is involved either structurally in inter-subunit H-bonding or directly in proton movements through the F1-ATPase.
mesh_terms: D000483:Alleles; D000596:Amino Acids / Q000032:analysis*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D046911:Macromolecular Substances; D008958:Models, Molecular; D009154:Mutation; D006180:Proton-Translocating ATPases / Q000032:analysis*; D011796:Quinacrine; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid
chemical_list: D000596:Amino Acids; D004269:DNA, Bacterial; D046911:Macromolecular Substances; D013386:Succinates; D019802:Succinic Acid; D006180:Proton-Translocating ATPases; D011796:Quinacrine