Novel components and enzymatic activities of the human erythrocyte plasma membrane calcium pump

FEBS Lett. 1997 Aug 4;412(3):592-6. doi: 10.1016/s0014-5793(97)00863-6.

Abstract

The plasma membrane Ca2+ pump is essential for the maintenance of cystolic calcium ion concentration levels in eukaryotes. Here we show that the Ca2+-ATPase, purified from human erythrocytes, contains two homopolymers, poly(3-hydroxybutyrate) (PHB) and inorganic polyphosphate (polyP), which form voltage-activated calcium channels in the plasma membranes of Escherichia coli and other bacteria. Furthermore, we demonstrate that the plasma membrane Ca2+-ATPase may function as a polyphosphate kinase, i.e. it exhibits ATP-polyphosphate transferase and polyphosphate-ADP transferase activities. These findings suggest a novel supramolecular structure for the functional Ca2+-ATPase, and a new mechanism of uphill Ca2+ extrusion coupled to ATP hydrolysis.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adenosine Triphosphate / blood
  • Calcium / blood
  • Calcium Channels / blood*
  • Calcium Channels / chemistry*
  • Calcium-Transporting ATPases / blood
  • Erythrocyte Membrane / chemistry*
  • Erythrocyte Membrane / enzymology*
  • Humans
  • Hydroxybutyrates / metabolism
  • Phosphorylation
  • Phosphotransferases (Phosphate Group Acceptor) / blood
  • Polyesters / metabolism
  • Polyphosphates / blood

Substances

  • Calcium Channels
  • Hydroxybutyrates
  • Polyesters
  • Polyphosphates
  • poly-beta-hydroxybutyrate
  • Adenosine Triphosphate
  • Phosphotransferases (Phosphate Group Acceptor)
  • polyphosphate kinase
  • Calcium-Transporting ATPases
  • Calcium