Reusch R N, Huang R, Kosk-Kosicka D
Department of Microbiology, Michigan State University, East Lansing 48824, USA.
FEBS Lett. 1997 Aug 4;412(3):592-6. doi: 10.1016/s0014-5793(97)00863-6.
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.
质膜Ca2+泵对于维持真核生物胞质钙离子浓度水平至关重要。我们在此表明，从人红细胞中纯化得到的Ca2+-ATP酶含有两种均聚物，聚（3-羟基丁酸酯）（PHB）和无机多聚磷酸盐（多聚P），它们在大肠杆菌和其他细菌的质膜中形成电压激活的钙通道。此外，我们证明质膜Ca2+-ATP酶可能作为一种多聚磷酸盐激酶发挥作用，即它表现出ATP-多聚磷酸盐转移酶和多聚磷酸盐-ADP转移酶活性。这些发现提示了功能性Ca2+-ATP酶的一种新型超分子结构，以及一种与ATP水解偶联的Ca2+上坡转运新机制。
