Szilagyi L, Lu R C
Biochim Biophys Acta. 1982 Dec 20;709(2):204-11. doi: 10.1016/0167-4838(82)90462-9.
The interactions of actin with myosin subfragment-1 and tropomyosin were explored by comparing the reactivities of lysine residues in F-actin alone with those in F-actin complexed to the other proteins. Limited reductive methylation was carried out on F-actin and the F-actin complexes with [14C]HCHO and [3H]HCHO, respectively. After dissociation from the other components, [3H]actin was combined with [14C]actin and 3H/14C of each lysine residue was measured. Myosin subfragment-1 reduced the reactivities of Lys-335 and Lys-372, while tropomyosin reduced those of Lys-237, -325, 327 and -335. When troponin was present in the absence of Ca2+, the effect of tropomyosin on Lys-335 remained the same, but its reactivity was completely restored upon the addition of Ca2+. Thus, the results suggest that different parts of actin are affected by the interaction with myosin subfragment-1 and tropomyosin, but the region containing Lys-335 is commonly affected by the presence of either of them. The change in reactivity is attributable either to a direct steric effect or to an induced conformational effect.
通过比较单独的F-肌动蛋白中赖氨酸残基与与其他蛋白质复合的F-肌动蛋白中赖氨酸残基的反应性，研究了肌动蛋白与肌球蛋白亚片段-1和原肌球蛋白的相互作用。分别用[14C]甲醛和[3H]甲醛对F-肌动蛋白及F-肌动蛋白复合物进行有限的还原甲基化。从其他组分解离后，将[3H]肌动蛋白与[14C]肌动蛋白混合，并测定每个赖氨酸残基的3H/14C。肌球蛋白亚片段-1降低了Lys-335和Lys-372的反应性，而原肌球蛋白降低了Lys-237、-325、327和-335的反应性。当在没有Ca2+的情况下存在肌钙蛋白时，原肌球蛋白对Lys-335的影响保持不变，但加入Ca2+后其反应性完全恢复。因此，结果表明肌动蛋白的不同部分受与肌球蛋白亚片段-1和原肌球蛋白相互作用的影响，但含有Lys-335的区域通常受它们中任何一个的存在影响。反应性的变化可归因于直接的空间效应或诱导的构象效应。
