Malencik D A, Heizmann C W, Fischer E H
Biochemistry. 1975 Feb 25;14(4):715-21. doi: 10.1021/bi00675a011.
As part of a study on the evolutionary aspects of control mechanisms, a number of structural muscle components from the Pacific dogfish (Squalus acanthias) are described. These include troponin, tropomyosin, actin, and myosin. Troponin (mol wt 108.000) was resolved into its constitutive subunits, repeated by a 20,500 mol wt fragment which binds 2 mol of Ca2+/mol with a KDiss of 0.91 mum, and an inhibitory component of 30,000 and a 58,000 component which are necessary for the calcium sensitivity of actomyosin ATPase. Tropomyosin and actin share many properties with their counterparts from higher vertebrates. Proteins similar to parvalbumins, i.e., the low molecular weight calcium-binding proteins widely distributed in fish, amphibians, and mammalian muscle, could be generated from troponin and its calcium-binding subunit by limited proteolysis. The appearance of immunological cross-reactivity and other similar features suggested some identity, but differences in the amino acid analysis exclude the possiblity that parvalbumins occur as breakdown products of troponin. The close relationship between parvalbumins and the calcium-binding subunit brings additional evidence that these proteins have arisen through divergent evolution.
作为一项关于控制机制进化方面研究的一部分，本文描述了来自太平洋角鲨（棘鲨）的一些肌肉结构成分。这些成分包括肌钙蛋白、原肌球蛋白、肌动蛋白和肌球蛋白。肌钙蛋白（分子量108,000）被分解为其组成亚基，由一个分子量为20,500的片段重复组成，该片段以0.91μm的解离常数结合2摩尔Ca2+/摩尔，还有一个30,000的抑制成分和一个58,000的成分，它们对于肌动球蛋白ATP酶的钙敏感性是必需的。原肌球蛋白和肌动蛋白与其高等脊椎动物的对应物具有许多共同特性。类似于小清蛋白的蛋白质，即广泛分布于鱼类、两栖类和哺乳类肌肉中的低分子量钙结合蛋白，可以通过有限的蛋白水解作用从肌钙蛋白及其钙结合亚基产生。免疫交叉反应性和其他类似特征的出现表明存在一定的同一性，但氨基酸分析的差异排除了小清蛋白作为肌钙蛋白分解产物出现的可能性。小清蛋白与钙结合亚基之间的密切关系提供了额外的证据，表明这些蛋白质是通过趋异进化产生的。
