Interactions of the actin and nucleotide binding sites on myosin subfragment 1.
Interactions of the actin and nucleotide binding sites on myosin subfragment 1.
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肌球蛋白亚片段 1 上肌动蛋白和核苷酸结合位点的相互作用。
DOI：
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发表时间：
1976
影响因子：
4.8
通讯作者：
S. Highsmith
中科院分区：
文献类型：
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作者：
S. Highsmith
在0.15M KCl4℃、pH 7.0条件下，用时间分辨荧光去偏振法测定了不同核苷酸(N)对肌球蛋白亚段1(S-1)和纯F-肌动蛋白(A)结合的影响。测定了ADP镁盐、腺基-5‘-酰亚胺二磷酸AMP-P(NH)P和PPI的缔合常数K’a、K‘n和K’n。根据其与肌动蛋白结合部位的相互作用，绘制了S-1的核苷酸结合部位图。各亚基对ATP结合的β-和γ-磷酰基的影响最大。相互作用的定量度量-相互作用自由能定义为-RT ln(Ka/K‘a)。ADP的K‘a为2.7×10(5)M-1，相互作用自由能为-4.67kJ·M-1。AMP-P(NH)P和PPI的降幅要大得多。在有镁离子存在的情况下，腺苷二磷酸、S-1和肌动蛋白存在三元复合体，AMP-P(NH)P和PPI的测定表明，三磷酸腺苷也可能形成三元复合体。根据这些结果，对(S-1)-肌动蛋白解离的机理进行了讨论。
The effects of selected nucleotides (N) on the binding of myosin subfragment 1 (S-1) and pure F-actin (A) were measured by time-resolved fluorescence depolarization for 0.15 M KCl, pH 7.0 at 4 degrees. The association constants K'A, KN, and K'N in the scheme (see article), were determined for the magnesium salts of ADP, adenyl-5'-yl imidodiphosphate AMP-P(NH)P, and PPi. The nucleotide binding site on S-1 was "mapped" with respect to its interaction on the actin binding site. The subsites were the beta- and gamma-phosphoryl groups of ATP bind had the largest effects. A quantitative measure of the interaction, the interaction free energy, was defined as -RT ln (KA/K'A). For ADP, K'A was 2.7 X 10(5) M-1 and the interaction free energy was -4.67 kJ M-1. For AMP-P(NH)P and PPi it was much larger. A ternary complex was shown to exist for ADP, S-1, and actin in the presence of Mg2+ and evidence from AMP-P(NH)P and PPi measurements indicated that ATP also likely forms a ternary complex. The mechanism of (S-1)-actin dissociation is discussed in light of these results.