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  • Title: The phosphorylation site of the Kdp-ATPase of Escherichia coli: site-directed mutagenesis of the aspartic acid residues 300 and 307 of the KdpB subunit.
    Author: Puppe W, Siebers A, Altendorf K.
    Journal: Mol Microbiol; 1992 Dec; 6(23):3511-20. PubMed ID: 1474895.
    Abstract:
    The potassium-translocating Kdp-ATPase of Escherichia coli shares common functional properties with eukaryotic P-type ATPases. The KdpB subunit has been identified as the catalytic subunit forming the phosphorylated intermediate. Substitution of Asp-307 in KdpB by Glu, Asn, Gln, Tyr, His, Ala or Ser by site-directed mutagenesis and the subsequent transfer of the point mutations to the chromosome revealed that the mutants were not functioning with respect to cell growth at low K+ concentrations and ATPase activity as well as phosphorylation capacity of the purified Kdp complex. These findings indicate that Asp-307 in KdpB is the phosphorylation site of the Kdp-ATPase. In contrast, replacement of the close but non-conserved Asp-300 by Asn or Glu has no immediate influence on the enzyme functions tested. However, the Km for K+ of the ATPase activity has been increased 30-fold compared with the wild-type enzyme.
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