钙诱导肌钙蛋白C二聚化。

Calcium-induced dimerization of troponin-C.

作者信息

Margossian S S, Stafford W F

出版信息

J Biol Chem. 1982 Feb 10;257(3):1160-5.

Abstract

Calcium-dependent self-association of rabbit skeletal troponin-C was investigated by equilibrium ultracentrifugation. Troponin-C which was homogeneous by the criterion of polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate was shown to undergo reversible dimerization (K2,app = 1.7 X 10(3) M-1) even in the presence of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) (0.1-1.0 M KCl, 0.01 M imidazole, 0.005 M potassium phosphate, 0.4 mM EGTA (pH 7.0), 1.0 mM dithiothreitol). The existence of a monomer-dimer reaction under these conditions could be demonstrated as long as the effects of the Donnan equilibrium were taken into account. The value of the observed second virial coefficient was consistent with the value expected from troponin-C at this pH. The dimerization could be enhanced by the addition of calcium to 0.1 mM (K2,app = 1.2 X 10(4) M-1). A monomer molecular weight of 18,700 was estimated from a "two-species" plot of the data. The effect of calcium was completely reversible.

摘要

通过平衡超速离心法研究了兔骨骼肌肌钙蛋白-C的钙依赖性自我缔合。在十二烷基硫酸钠存在下，经聚丙烯酰胺凝胶电泳鉴定为均一的肌钙蛋白-C，即使在存在乙二醇双（β-氨基乙醚）-N，N，N'，N'-四乙酸（EGTA）（0.1 - 1.0 M KCl，0.01 M咪唑，0.005 M磷酸钾，0.4 mM EGTA（pH 7.0），1.0 mM二硫苏糖醇）的情况下，也显示出可逆的二聚化（K2,app = 1.7×10³ M⁻¹）。只要考虑到唐南平衡的影响，就可以证明在这些条件下存在单体-二聚体反应。观察到的第二维里系数的值与该pH下肌钙蛋白-C预期的值一致。加入钙至0.1 mM可增强二聚化（K2,app = 1.2×10⁴ M⁻¹）。根据数据的“双物种”图估计单体分子量为18,700。钙的作用是完全可逆的。