Head J F, Spielberg S, Kaminer B
Biochem J. 1983 Mar 1;209(3):797-802. doi: 10.1042/bj2090797.
We have isolated two Ca2+-binding proteins from squid optic lobes, each of which is also able to bind phenothiazines in a Ca2+-dependent manner. These proteins have each been purified and partly characterized. One of the proteins corresponds to calmodulin, in that it has a similar amino acid content to bovine brain calmodulin, including a single residue of trimethyl-lysine, it co-migrates with bovine calmodulin both on alkaline-urea- and on sodium dodecyl sulphate (SDS)/polyacrylamide-gel electrophoresis, and will activate calmodulin-dependent phosphodiesterase. The second protein has the same subunit molecular weight as calmodulin, as determined by SDS/polyacrylamide-gel electrophoresis, Mr 17 000, but migrates more slowly than this protein on alkaline-urea-gel electrophoresis. It has an amino acid composition distinct from calmodulin, containing no trimethyl-lysine, its CNBr fragments migrate on alkaline gels in a pattern distinct from those of calmodulin and it shows little ability to activate phosphodiesterase. The u.v.-absorption spectra of the proteins indicate the absence of tryptophan and the presence of a high phenylalanine/tyrosine ratio in each. Both proteins also bind 3-4 calcium ions/mol at 0.1 mM-free Ca2+ and each binds chlorpromazine in a Ca2+-dependent manner.
我们从鱿鱼视叶中分离出了两种钙结合蛋白，它们每一种都能以钙依赖的方式结合吩噻嗪类药物。这两种蛋白均已被纯化并进行了部分特性鉴定。其中一种蛋白与钙调蛋白相对应，因为它的氨基酸组成与牛脑钙调蛋白相似，包括一个三甲基赖氨酸残基，在碱性尿素和十二烷基硫酸钠（SDS）/聚丙烯酰胺凝胶电泳中它与牛钙调蛋白迁移率相同，并且能激活钙调蛋白依赖性磷酸二酯酶。通过SDS/聚丙烯酰胺凝胶电泳测定，第二种蛋白的亚基分子量与钙调蛋白相同，为17000，但在碱性尿素凝胶电泳中其迁移速度比该蛋白慢。它的氨基酸组成与钙调蛋白不同，不含三甲基赖氨酸，其溴化氰片段在碱性凝胶上的迁移模式与钙调蛋白不同，并且它激活磷酸二酯酶的能力较弱。蛋白质的紫外吸收光谱表明每种蛋白都不含色氨酸且苯丙氨酸/酪氨酸比例较高。两种蛋白在游离钙离子浓度为0.1 mM时每摩尔还能结合3 - 4个钙离子，并且每种蛋白都以钙依赖的方式结合氯丙嗪。
