title: Novel components and enzymatic activities of the human erythrocyte plasma membrane calcium pump.
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.
authors.affiliation: Department of Microbiology, Michigan State University, East Lansing 48824, USA. rnreusch@msu.edu
authors.forename: R N
authors.initials: RN
authors.lastname: Reusch
authors.forename: R
authors.initials: R
authors.lastname: Huang
authors.forename: D
authors.initials: D
authors.lastname: Kosk-Kosicka
mesh_terms: D000255:Adenosine Triphosphate / Q000097:blood; D002118:Calcium / Q000097:blood; D015220:Calcium Channels / Q000097:blood* / Q000737:chemistry*; D000252:Calcium-Transporting ATPases / Q000097:blood; D004910:Erythrocyte Membrane / Q000737:chemistry* / Q000201:enzymology*; D006801:Humans; D006885:Hydroxybutyrates / Q000378:metabolism; D010766:Phosphorylation; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000097:blood; D011091:Polyesters / Q000378:metabolism; D011122:Polyphosphates / Q000097:blood; D000091402:Prohibitins; D000094122:Polyhydroxybutyrates
chemical_list: D000255:Adenosine Triphosphate; D002118:Calcium; D015220:Calcium Channels; D000252:Calcium-Transporting ATPases; D006885:Hydroxybutyrates; D017856:Phosphotransferases (Phosphate Group Acceptor); D011091:Polyesters; D011122:Polyphosphates; D000091402:Prohibitins; C000717328:PHB protein, human; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates; C022424:polyphosphate kinase