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Serine Phosphorylation Regulates the P-type Potassium pump KdpFABC

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

INSTRUMENT(S): QExactive HF ThermoScientific

ORGANISM(S): Escherichia Coli

SUBMITTER: Thomas A. Neubert

PROVIDER: MSV000084906 | MassIVE | Wed Feb 05 12:45:00 GMT 2020

REPOSITORIES: MassIVE

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Serine Phosphorylation Regulates the P-type Potassium pump KdpFABC

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