Golitsina N L, Bobkov A A, Dedova I V, Pavlov D A, Nikolaeva O P, Orlov V N, Levitsky D I
A. N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Russia.
J Muscle Res Cell Motil. 1996 Aug;17(4):475-85. doi: 10.1007/BF00123363.
The effects of various modifications of rabbit skeletal myosin subfragment 1 on the thermal denaturation of subfragment 1 in ternary complexes with Mg-ADP and orthovanadate (V1) or beryllium fluoride (BeFx) have been studied by differential scanning calorimetry. It has been shown that specific modifications of SH1 group of Cys-707 by different sulfhydryl reagents, trinitrophenylation of Lys-83, and reductive methylation of lysine residues promote the decomposition of the S1.ADP.Vi complex and change the character of structural transitions of the subfragment 1 molecule induced by the formation of this complex, but they have much less or no influence on subfragment 1 thermal stability in the S1.ADP.BeFx complex. Thus, the differential scanning calorimetric studies on modified subfragment 1 preparations reveal a significant difference between S1.ADP.Vi and S1.ADP.BeFx complexes. It is suggested that S1.ADP.Vi and S1.ADP.BeFx complexes represent structural analogues of different transition states of the ATPase cycle, namely the intermediate states S1**.ADP.Pi and S1*.ATP, respectively. It is also proposed that during formation of the S1.ADP.Vi complex the region containing both Cys-707 and Lys-83 plays an important role in the spread of conformational changes from the active site of subfragment 1 ATPase throughout the structure of the entire subfragment 1 molecule. In such a case, the effects of reductive methylation of lysine residues on the subfragment 1 structure in the S1.ADP.Vi complex are related to the modification of Lys-83.
通过差示扫描量热法研究了兔骨骼肌肌球蛋白亚片段1的各种修饰对其与Mg-ADP和原钒酸盐（V1）或氟化铍（BeFx）形成的三元复合物中亚片段1热变性的影响。结果表明，不同巯基试剂对Cys-707的SH1基团进行特异性修饰、Lys-83的三硝基苯化以及赖氨酸残基的还原甲基化促进了S1.ADP.Vi复合物的分解，并改变了由该复合物形成诱导的亚片段1分子结构转变的特征，但它们对S1.ADP.BeFx复合物中亚片段1的热稳定性影响很小或没有影响。因此，对修饰后的亚片段1制剂进行的差示扫描量热研究揭示了S1.ADP.Vi和S1.ADP.BeFx复合物之间的显著差异。有人提出，S1.ADP.Vi和S1.ADP.BeFx复合物分别代表ATP酶循环不同过渡态的结构类似物，即中间态S1**.ADP.Pi和S1*.ATP。还提出，在形成S1.ADP.Vi复合物的过程中，包含Cys-707和Lys-83的区域在亚片段1 ATP酶活性位点的构象变化扩展到整个亚片段1分子结构中起着重要作用。在这种情况下，赖氨酸残基的还原甲基化对S1.ADP.Vi复合物中亚片段1结构的影响与Lys-83的修饰有关。
