Ca2+ Induces Spontaneous Dephosphorylation of a Novel P5A-type ATPase

Danny Mollerup Sorensen, Annette B. Moller, Mia K. Jakobsen, Michael Krogh Jensen, Peter Vangheluwe, Morten Jeppe Buch-Pedersen, Michael G. Palmgren

Research output: Contribution to journalJournal articleResearchpeer-review


P5 ATPases constitute the least studied group of P-type ATPases, an essential family of ion pumps in all kingdoms of life. Although P5 ATPases are present in every eukaryotic genome analyzed so far, they have remained orphan pumps, and their biochemical function is obscure. We show that a P5A ATPase from barley, HvP5A1, locates to the endoplasmic reticulum and is able to rescue knock-out mutants of P5A genes in both Arabidopsis thaliana and Saccharomyces cerevisiae. HvP5A1 spontaneously forms a phosphorylated reaction cycle intermediate at the catalytic residue Asp-488, whereas, among all plant nutrients tested, only Ca2+ triggers dephosphorylation. Remarkably, Ca2+-induced dephosphorylation occurs at high apparent [Ca2+] (K-i = 0.25 mM) and is independent of the phosphatase motif of the pump and the putative binding site for transported ligands located in M4. Taken together, our results rule out that Ca2+ is a transported substrate but indicate the presence of a cytosolic low affinity Ca2+-binding site, which is conserved among P-type pumps and could be involved in pump regulation. Our work constitutes the first characterization of a P5 ATPase phosphoenzyme and points to Ca2+ as a modifier of its function.

Original languageEnglish
JournalJournal of Biological Chemistry
Issue number34
Pages (from-to)28336-28348
Publication statusPublished - 2012
Externally publishedYes


  • Dicotyledones Angiospermae Spermatophyta Plantae (Angiosperms, Dicots, Plants, Spermatophytes, Vascular Plants) - Cruciferae [25880] Arabidopsis thaliana species
  • Fungi Plantae (Fungi, Microorganisms, Nonvascular Plants, Plants) - Ascomycetes [15100] Saccharomyces cerevisiae species
  • Monocotyledones Angiospermae Spermatophyta Plantae (Angiosperms, Monocots, Plants, Spermatophytes, Vascular Plants) - Gramineae [25305] Hordeum vulgare species barley common
  • Arabidopsis thaliana P5A gene [Cruciferae] mutant
  • Saccharomyces cerevisiae P5A gene [Ascomycetes] mutant
  • calcium ion 14127-61-8
  • HvP5A1 phosphorylation, aspartic acid-488, P5A-type ATPase
  • 03502, Genetics - General
  • 03504, Genetics - Plant
  • 10062, Biochemistry studies - Nucleic acids, purines and pyrimidines
  • 10069, Biochemistry studies - Minerals
  • 10802, Enzymes - General and comparative studies: coenzymes
  • 51518, Plant physiology - Enzymes
  • Enzymology
  • Molecular Genetics
  • enzyme activity
  • Biochemistry and Molecular Biophysics
  • endoplasmic reticulum
  • BAJ85414 GenBank, EMBL, DDJB nucleotide sequence
  • CA497971 GenBank, EMBL, DDJB nucleotide sequence
  • CB877529 GenBank, EMBL, DDJB nucleotide sequence


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