Chiesi M, Vorherr T, Falchetto R, Waelchli C, Carafoli E
Department of Research, Pharmaceuticals Division, CIBA-GEIGY Limited, Basel, Switzerland.
Biochemistry. 1991 Aug 13;30(32):7978-83. doi: 10.1021/bi00246a015.
The Ca2+ pumps of the plasma membrane (PM ATPase) and of sarcoplasmic reticulum (SR ATPase) share a number of structural and functional properties. A major difference is the regulatory mechanism. The PM ATPase contains a C-terminal autoinhibitory domain; calmodulin binds to it, removing the inhibition. The SR ATPase contains a domain that interacts with the inhibitor protein phospholamban when the latter is in the nonphosphorylated state; phosphorylation of phospholamban removes the inhibition. Peptides corresponding to the autoinhibitory domain of the PM ATPase were synthesized and found to inhibit the SR ATPase. A 28-residue peptide (C28W), containing the entire autoinhibitory domain, was the most powerful (IC50 = 15 microM; lmax greater than 90%). The inhibition was Ca2+ dependent and more pronounced at submicromolar Ca2+ concentrations. C28W is about 50% homologous to the cytosolic domain of phospholamban, the hydrophilic portion of which was found to interact directly with calmodulin (Kd = about 700 nM). However, while calmodulin reversed the inhibition of the SR ATPase by C28W, it failed to reverse that induced by nonphosphorylated phospholamban.
质膜的Ca2+泵（PM ATPase）和肌浆网的Ca2+泵（SR ATPase）具有许多结构和功能特性。一个主要区别在于调节机制。PM ATPase含有一个C末端自身抑制结构域；钙调蛋白与之结合，解除抑制。SR ATPase含有一个结构域，当抑制蛋白受磷蛋白处于非磷酸化状态时，该结构域与之相互作用；受磷蛋白的磷酸化解除抑制。合成了与PM ATPase自身抑制结构域对应的肽段，发现其可抑制SR ATPase。一种包含整个自身抑制结构域的28个残基的肽（C28W）作用最强（IC50 = 15 microM；最大抑制率大于90%）。这种抑制作用依赖于Ca2+，在亚微摩尔Ca2+浓度时更为明显。C28W与受磷蛋白的胞质结构域约有50%的同源性，已发现受磷蛋白的亲水部分可直接与钙调蛋白相互作用（解离常数Kd约为700 nM）。然而，虽然钙调蛋白可逆转C28W对SR ATPase的抑制作用，但它不能逆转非磷酸化受磷蛋白所诱导的抑制作用。
