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Novel components and enzymatic activities of the human erythrocyte plasma membrane calcium pump
Author(s) -
Reusch Rosetta N,
Huang Ruiping,
Kosk-Kosicka Danuta
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)00863-6
Subject(s) - polyphosphate , atpase , plasma membrane ca2+ atpase , membrane , atp hydrolysis , chemistry , biochemistry , calcium , enzyme , biophysics , calcium pump , biology , phosphate , organic chemistry
The plasma membrane Ca 2+ pump is essential for the maintenance of cystolic calcium ion concentration levels in eukaryotes. Here we show that the Ca 2+ ‐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 Ca 2+ ‐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 Ca 2+ ‐ATPase, and a new mechanism of uphill Ca 2+ extrusion coupled to ATP hydrolysis.