Takagi T, Konishi K
J Biochem. 1984 Jun;95(6):1603-15. doi: 10.1093/oxfordjournals.jbchem.a134773.
The isotypes of sarcoplasmic Ca2+ binding protein (SCP) were purified from shrimp tail muscle. SCP exists in a dimeric form. One sample of shrimp contained only alpha A chain, whereas another contained alpha B and beta chains, and a heterodimer of alpha B beta which was not analyzed precisely. The amino acid sequences of the two alpha chains were determined. The two alpha chains are composed of 190 and 192 amino acid residues, respectively. The sequences of the two alpha chains differed in only four amino acids out of 192 residues. The sequences indicate that the alpha chain has three Ca2+-binding sites which are common to EF-hand type Ca2+-binding protein. In the absence of added Ca2+ and Mg2+, the amounts of bound Ca2+ in alpha A, alpha B, and beta chains were 3.0, 3.3, and 2.4 mol/22,000 g protein, respectively. Thus, it is suggested that all three isotypes of shrimp SCP have three Ca2+-binding sites which have high affinity to Ca2+. The sequence homology of shrimp SCP with other EF-hand type Ca2+-binding proteins is very low. The protein having the greatest homology with this SCP was cod parvalbumin; the sequence homology is 18%.
从虾尾肌肉中纯化出肌浆钙结合蛋白（SCP）的同种型。SCP以二聚体形式存在。一个虾样本仅含有αA链，而另一个含有αB链和β链，以及未精确分析的αBβ异二聚体。测定了两条α链的氨基酸序列。两条α链分别由190和192个氨基酸残基组成。两条α链的序列在192个残基中仅4个氨基酸不同。序列表明α链具有三个与EF手型钙结合蛋白共有的钙结合位点。在未添加Ca2+和Mg2+的情况下，αA、αB和β链中结合的Ca2+量分别为3.0、3.3和2.4 mol/22,000 g蛋白质。因此，提示虾SCP的所有三种同种型都具有对Ca2+具有高亲和力的三个钙结合位点。虾SCP与其他EF手型钙结合蛋白的序列同源性非常低。与该SCP具有最高同源性的蛋白质是鳕鱼副肌球蛋白；序列同源性为18%。
