Cachia P J, Van Eyk J, Ingraham R H, McCubbin W D, Kay C M, Hodges R S
Biochemistry. 1986 Jun 17;25(12):3553-62. doi: 10.1021/bi00360a013.
Recent studies using bee and wasp venom peptides have led to the hypothesis that proper complex formation with calmodulin (CaM) requires the presence of a basic amphiphilic helix on the surface of the target protein [Cox, J. A. (1984) Fed. Proc., Fed. Am. Soc. Exp. Biol. 43, 3000]. We have tested this hypothesis by examining CaM and troponin C (TnC) complex formation with two basic peptides, the wasp venom tetradecapeptide mastoparan and the physiologically relevant synthetic troponin I (TnI) inhibitory peptide [104-115], using far-ultraviolet circular dichroism as a secondary structure probe. Complex formation between mastoparan and either CaM or TnC results in an increase in helical content, whereas the helical content of TnI inhibitory peptide does not increase when bound to either protein. Significantly, mastoparan is 78% alpha-helical in a 50% solution of the helix-inducing solvent trifluoroethanol and has a high helix-forming potential according to the Chou-Fasman rules while TnI inhibitory peptide contains none and is not predicted to have any. We interpret these data as indicating that these peptides exhibit substantially different secondary structures upon binding to CaM or TnC. The ability of mastoparan to regulate the acto-subfragment 1-tropomyosin ATPase has also been examined. Mastoparan and TnI inhibitory peptide inhibited 31% and 45% of the activity, respectively. TnC and CaM promote differing degrees of Ca2+-sensitive release of inhibition by both peptides. Sequence comparison suggests that the basic residues present in both peptides are important for binding. However, we conclude that an alpha-helical structure is not a prerequisite for the binding of target proteins to CaM and TnC.
最近使用蜜蜂和黄蜂毒液肽的研究提出了一种假说，即与钙调蛋白（CaM）形成适当的复合物需要靶蛋白表面存在一个碱性两亲性螺旋[考克斯，J.A.（1984年）《联邦程序》，美国实验生物学联合会会刊43，3000]。我们通过使用远紫外圆二色性作为二级结构探针，研究CaM和肌钙蛋白C（TnC）与两种碱性肽（黄蜂毒液十四肽mastoparan和生理相关的合成肌钙蛋白I（TnI）抑制肽[104 - 115]）的复合物形成，对这一假说进行了测试。mastoparan与CaM或TnC之间的复合物形成导致螺旋含量增加，而TnI抑制肽与任何一种蛋白质结合时螺旋含量都不增加。值得注意的是，mastoparan在50%的螺旋诱导溶剂三氟乙醇溶液中78%为α螺旋，根据周-法斯曼规则具有很高的螺旋形成潜力，而TnI抑制肽不含α螺旋且预计也不会有。我们将这些数据解释为表明这些肽在与CaM或TnC结合时表现出显著不同的二级结构。还研究了mastoparan调节肌动蛋白亚片段1 - 原肌球蛋白ATP酶的能力。mastoparan和TnI抑制肽分别抑制了31%和45%的活性。TnC和CaM促进两种肽对钙敏感性抑制的不同程度释放。序列比较表明，两种肽中存在的碱性残基对结合很重要。然而，我们得出结论，α螺旋结构不是靶蛋白与CaM和TnC结合的先决条件。
