Stevens F C, Walsh M, Ho H C, Teo T S, Wang J H
J Biol Chem. 1976 Aug 10;251(15):4495-500.
In previous studies we have shown that the activation of bovine heart cyclic nucleotide phosphodiesterase by purified protein activator is completely dependent on the presence of Ca2+ and that the protein activator Ca2+ complex is probably the true activator for the enzyme (Teo, T.S. and Wang, J.H. (1973) J. Biol. Chem. 248, 5930-5955). More recent studies have led us to believe that the mechanism of the Ca2+ activation of phosphodiesterase resembles that of the Ca2+ activation of muscle contraction and that the protein activator may play a role similar to troponin. In the present study we show that the protein activator resembles rabbit muscle troponin C in amino acid composition, molecular weight, isoelectric point, and ultraviolet absorption spectrum. Preliminary structural studies also indicate that these two proteins may have evolved from a common ancestral protein through gene duplication. This argument is strengthened by the finding that the tryptic peptide map of the bovine heart protein activator is indistinguishable from that of the bovine brain phosphodiesterase activator protein for which preliminary sequence information also suggests homology to troponin C (Watterson, D.M., Harrelson, W.G., Jr., Keller, P.M., Sharief, F., and Vanaman, T.C. (1976) J. Biol. Chem. 251, 4501-4513).
在先前的研究中我们已经表明，纯化的蛋白激活剂对牛心脏环核苷酸磷酸二酯酶的激活完全依赖于Ca2+的存在，并且蛋白激活剂-Ca2+复合物可能是该酶真正的激活剂（Teo, T.S.和Wang, J.H. (1973) J. Biol. Chem. 248, 5930-5955）。最近的研究使我们相信，磷酸二酯酶的Ca2+激活机制类似于肌肉收缩的Ca2+激活机制，并且蛋白激活剂可能发挥类似于肌钙蛋白的作用。在本研究中我们表明，蛋白激活剂在氨基酸组成、分子量、等电点和紫外吸收光谱方面类似于兔肌肉肌钙蛋白C。初步的结构研究还表明，这两种蛋白质可能通过基因复制从一个共同的祖先蛋白质进化而来。牛心脏蛋白激活剂的胰蛋白酶肽图与牛脑磷酸二酯酶激活蛋白的胰蛋白酶肽图无法区分，这一发现进一步支持了这一观点，对于牛脑磷酸二酯酶激活蛋白，初步的序列信息也表明其与肌钙蛋白C具有同源性（Watterson, D.M., Harrelson, W.G., Jr., Keller, P.M., Sharief, F., and Vanaman, T.C. (1976) J. Biol. Chem. 251, 4501-4513）。
