Serine phosphorylation regulates the P-type potassium pump KdpFABC

Elife. 2020 Sep 21;9:e55480. doi: 10.7554/eLife.55480.

Abstract

KdpFABC is an ATP-dependent K+ pump that ensures bacterial survival in K+-deficient environments. Whereas transcriptional activation of kdpFABC expression is well studied, a mechanism for down-regulation when K+ levels are restored has not been described. Here, we show that KdpFABC is inhibited when cells return to a K+-rich environment. The mechanism of inhibition involves phosphorylation of Ser162 on KdpB, which can be reversed in vitro by treatment with serine phosphatase. Mutating Ser162 to Alanine produces constitutive activity, whereas the phosphomimetic Ser162Asp mutation inactivates the pump. Analyses of the transport cycle show that serine phosphorylation abolishes the K+-dependence of ATP hydrolysis and blocks the catalytic cycle after formation of the aspartyl phosphate intermediate (E1~P). This regulatory mechanism is unique amongst P-type pumps and this study furthers our understanding of how bacteria control potassium homeostasis to maintain cell volume and osmotic potential.

Keywords: E. coli; biochemistry; chemical biology; membrane transport; molecular biophysics; p-type atpase; potassium homeostasis; serine phosphorylation; structural biology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism*
  • Cation Transport Proteins / chemistry
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Mutation / genetics
  • P-type ATPases / chemistry
  • P-type ATPases / genetics
  • P-type ATPases / metabolism*
  • Phosphorylation / genetics
  • Potassium / metabolism*
  • Serine / metabolism*

Substances

  • Cation Transport Proteins
  • Escherichia coli Proteins
  • Serine
  • Adenosine Triphosphatases
  • potassium translocating Kdp-ATPase, E coli
  • P-type ATPases
  • Potassium