Penniston J T, Enyedi A
Department of Biochemistry and Molecular Biology, Mayo Foundation, Rochester, MN 55905, USA.
J Membr Biol. 1998 Sep 15;165(2):101-9. doi: 10.1007/s002329900424.
The plasma membrane calcium pump, which ejects Ca2+ from the cell, is regulated by calmodulin. In the absence of calmodulin, the pump is relatively inactive; binding of calmodulin to a specific domain stimulates its activity. Phosphorylation of the pump with protein kinase C or A may modify this regulation. Most of the regulatory functions of the enzyme are concentrated in a region at the carboxyl terminus. This region varies substantially between different isoforms of the pump, causing substantial differences in regulatory properties. The pump shares some motifs of the carboxyl terminus with otherwise unrelated proteins: The calmodulin-binding domain is a modified IQ motif (a motif which is present in myosins) and the last 3 residues of isoform 4b are a PDZ target domain. The pump is ubiquitous, with isoforms 1 and 4 of the pump being more widely distributed than 2 and 3. In some kinds of cells isoform 1 or 4 is missing, and is replaced by another isoform.
将钙离子从细胞中排出的质膜钙泵受钙调蛋白调节。在没有钙调蛋白的情况下，该泵相对不活跃；钙调蛋白与特定结构域的结合会刺激其活性。蛋白激酶C或A对该泵的磷酸化作用可能会改变这种调节。该酶的大多数调节功能集中在羧基末端的一个区域。该区域在泵的不同亚型之间有很大差异，导致调节特性存在显著差异。该泵与其他不相关的蛋白质在羧基末端有一些基序：钙调蛋白结合结构域是一个修饰的IQ基序（一种存在于肌球蛋白中的基序），亚型4b的最后3个残基是一个PDZ靶结构域。该泵普遍存在，泵的亚型1和4比2和3分布更广泛。在某些类型的细胞中，亚型1或4缺失，由另一种亚型替代。
