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  • Title: Fo portion of Escherichia coli H+-ATPase. Carboxyl-terminal region of the b subunit is essential for assembly of functional Fo.
    Author: Takeyama M, Noumi T, Maeda M, Futai M.
    Journal: J Biol Chem; 1988 Nov 05; 263(31):16106-12. PubMed ID: 2903150.
    Abstract:
    Six chromosomal uncF mutants of Escherichia coli defective in the b subunit of H+-ATPase (156 amino acid residues) were identified (KF92, Met-1----Val; KF164, Gln-64----end; KF61 and KF144, Gln-104----end; KF138, Gln-106----end; and KF79, Gln-123----end). The membranes of all these mutants had low ATPase activities (less than 5% of that of the wild type), and no functional H+ pathway, although the truncated b subunits were integrated into these membranes. These findings suggest that about 30 carboxyl-terminal amino acid residues of the b subunit are essential for formation of the F1-binding site and H+ pathway. For examination of the role(s) of the carboxyl-terminal region(s) or residue(s) of the b subunit, recombinant plasmids carrying truncated uncF genes of various lengths were constructed by in vitro muta-genesis and introduced into a recA1 derivative of strain KF92 (Met-1----Val). Analyses of the membranes from the resulting strains demonstrated that almost the entire carboxyl-terminal region of the b subunit is necessary for formation of functional Fo, since loss of the carboxyl-terminal residue resulted in significant reduction of both F1 binding and H+ translocation, and loss of two or more residues abolished both activities completely.
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