Pavlov D A, Sobieszek A, Levitsky D I
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899, Russia.
Biochemistry (Mosc). 1998 Aug;63(8):952-62.
The thermal unfolding of turkey gizzard smooth muscle myosin subfragment 1 (S1) and heavy meromyosin (HMM) in the absence of added nucleotides, in the presence of ADP, and in S1 or HMM ternary complexes with ADP and Pi analogs, orthovanadate (Vi), beryllium fluoride (BeFx), or aluminum fluoride (AlF4-), have been studied by differential scanning calorimetry (DSC). It has been shown that the formation of these ternary complexes causes significant structural changes in S1 or in the heads of HMM which are reflected in a pronounced increase of the protein thermal stability. The effect of BeFx was less distinct than that of AlF4- or Vi. Phosphorylation of regulatory light chains (RLC) in S1 or in HMM had practically no influence on these effects. In general, the changes caused by various Pi analogs in smooth muscle S1 or HMM were similar to those observed earlier with skeletal muscle S1 devoid of RLC. It is concluded that RLC and their phosphorylation do not significantly affect the character of structural changes induced in motor domains of the HMM heads by the formation of ternary complexes HMM--ADP--Vi, HMM--ADP--AlF4-, and HMM--ADP--BeFx--stable analogs of the intermediate states of the HMM ATPase reaction, HMM.ADP.Pi and HMM. ATP.
通过差示扫描量热法（DSC）研究了火鸡砂囊平滑肌肌球蛋白亚片段1（S1）和重酶解肌球蛋白（HMM）在未添加核苷酸、存在ADP以及在与ADP和磷酸类似物、原钒酸盐（Vi）、氟化铍（BeFx）或氟化铝（AlF4-）形成的S1或HMM三元复合物中的热解折叠情况。结果表明，这些三元复合物的形成会导致S1或HMM头部发生显著的结构变化，这表现为蛋白质热稳定性的显著提高。BeFx的作用不如AlF4-或Vi明显。S1或HMM中调节轻链（RLC）的磷酸化对这些作用几乎没有影响。总体而言，各种磷酸类似物在平滑肌S1或HMM中引起的变化与早期在不含RLC的骨骼肌S1中观察到的变化相似。得出的结论是，RLC及其磷酸化不会显著影响由HMM-ADP-Vi、HMM-ADP-AlF4-和HMM-ADP-BeFx（HMM ATPase反应中间状态HMM.ADP.Pi和HMM.ATP的稳定类似物）三元复合物的形成在HMM头部运动结构域中诱导的结构变化特征。
