Enyedi A, Verma A K, Heim R, Adamo H P, Filoteo A G, Strehler E E, Penniston J T
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905.
J Biol Chem. 1994 Jan 7;269(1):41-3.
The plasma membrane Ca2+ pump is a calmodulin-regulated P-type ATPase that is an essential element in controlling intracellular Ca2+ concentration. Studies on the gene structure of this pump have revealed an alternate splice option that changes the structure of the calmodulin-binding domain. This change in the structure of the enzyme results in a reduced calmodulin affinity. Tests of the enzyme's activity in the presence of a high calmodulin concentration, approximating that found inside living cells, show that this reduced calmodulin affinity causes a reduced apparent affinity of the enzyme for Ca2+. This shift in the Ca2+ activation occurs in a Ca2+ concentration range crucial to cellular function and is probably the physiologically important consequence of the alternate splice.
质膜钙泵是一种受钙调蛋白调节的P型ATP酶，是控制细胞内钙浓度的关键要素。对该泵基因结构的研究揭示了一种可变剪接方式，这种方式改变了钙调蛋白结合域的结构。酶结构的这种变化导致钙调蛋白亲和力降低。在高钙调蛋白浓度（接近活细胞内的浓度）条件下对该酶活性进行测试，结果表明钙调蛋白亲和力降低会导致该酶对钙离子的表观亲和力下降。钙离子激活的这种变化发生在对细胞功能至关重要的钙离子浓度范围内，可能是可变剪接在生理上的重要结果。
