Cells
Publication:

Mutational analysis of the function of the a-subunit of the F0F1-APPase of Escherichia coli (1990)

Author(s): S. M. Howitt;R. N. Lightowlers;F. Gibson;G. B. Cox

  • : Mutational analysis of the function of the a-subunit of the F0F1-APPase of Escherichia coli

Abstract: In a model proposed for the structure of the a-subunit of the Escherichia coli F0F1-ATPase (Howitt, S.M., Gibson, F. and Cox, G.B. (1988) Biochim. Biophys. Acta 936, 74-80), a cluster of charged residues, including one arginine and four aspartic acid residues, lie on the periplasmic side of the membrane. On the cytoplasmic side, three pairs of lysine residues and an arginine residue are present. Site-directed mutagenesis was used to investigate the roles of these residues. It was found that none was directly involved in the proton pore. However, the substitutions of Asp-124 or Asp-44 by asparagine or Arg-140 by glutamine had similar effects in that the membranes from such mutants from which the F1-ATPase was removed were proton-impermeable. A combination of the Asp-44 mutation with either the Asp-124 or Arg-140 mutations in the same strain resulted in complete loss of oxidative phosphorylation. It was tentatively concluded that Asp-124 and Arg-140 form a salt bridge, as did Asp-44 with an unknown residue, and these salt bridges were concerned with the maintenance of correct a-subunit structure. Further support for this conclusion was obtained when second site revertants of a Glu-219 to histidine mutant were found to have either histidine or leucine replacing Arg-140. Thus, the lack of the Asp-124/Arg-140 salt bridge might enable repositioning of the helices of the a-subunit such that His-219 becomes a functional component of the proton pore.

Notes: 0006-3002 Journal Article

  • Short Title: Mutational analysis of the function of the a-subunit of the F0F1-APPase of Escherichia coli
  • Date: Feb 2
  • Journal: Biochim Biophys Acta
  • Volume: 1015
  • Issue: 2
  • Pages: 264-8
  • Publication type: Article
  • Bibliographic status: Published

Keywords: Base Sequence DNA Mutational Analysis Escherichia coli/*enzymology Membrane Proteins/genetics/physiology/ultrastructure Molecular Sequence Data Proton-Translocating ATPases/*genetics/physiology Research Support, Non-U.S. Gov't Structure-Activity Relationship

Staff

Professor Robert Lightowlers
Director, ICaMB and Professor of Molecular Neuroscience