Plasma membrane Ca2+ pump isoforms 2a and 2b are unusually responsive to calmodulin and Ca2+
Plasma membrane Ca2+ pump isoforms 2a and 2b are unusually responsive to calmodulin and Ca2+
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DOI：
10.1074/jbc.272.29.17981
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发表时间：
1997-07-18
影响因子：
4.8
通讯作者：
Penniston, JT
中科院分区：
文献类型：
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作者：
Elwess, NL;Filoteo, AG;Penniston, JT
构建了大鼠质膜钙泵的全长a和b变体，并在COS-7细胞中表达了这些异构体，为了表征这些异构体，测定了微粒体部分的钙转运，rPMCA2a和rPMCA2b对钙调蛋白的亲和力都比相应的hPMCA4高得多，rPMCA2b在迄今测试的异构体中亲和力最高，当分析到相对较高的钙调蛋白浓度时，rPMCA2b和rPRMCA2a显示出更高的表观钙亲和力；即，当钙浓度低于hPMCA4b时，它们对钙的亲和力更高。这表明，这两个变体的大鼠异构体2将倾向于保持较低的细胞内游离钙水平的表达，这两个变体也显示出更高的基础活性水平(在完全没有钙调素)比hPMCA4b，这一特性将加强他们的能力，以保持较低的细胞内游离钙浓度，实验旨在确定更高的来源的rPMCA2b的表观钙亲和力较高的来源表明，它来自羧基末端的性质，而不是任何催化核心的差异。
The full-length a and b variants of the rat plasma membrane calcium pump, isoform 2 (rPMCA2a and rPMCA2b), were constructed and expressed in COS-7 cells, To characterize these isoforms, calcium transport was determined in a microsomal fraction, Both rPMCA2a and rPMCA2b had a much higher affinity for calmodulin than the corresponding forms of hPMCA4, and rPMCA2b had the highest affinity among the isoforms that have been tested so far, When analyzed at a relatively high calmodulin concentration, rPMCA2b and, to a lesser extent, rPRMCA2a showed higher apparent calcium affinity; i.e. they were more active at lower Ca2+ concentrations than hPMCA4b. This indicates that these two variants of rat isoform 2 will tend to maintain a lower free cytosolic Ca2+ level in cells where they are expressed, Both variants also showed a higher level of basal activity (in the complete absence of calmodulin) than hPMCA4b, a property which would reinforce their ability to maintain a low free cytosolic Ca2+ concentration, Experiments designed to determine the source of the higher apparent Ca2+ affinity of rPMCA2b showed that it came from the properties of the carboxyl terminus, rather than from any difference in the catalytic core.