Differential scanning calorimetry of the unfolding of myosin subfragment 1, subfragment 2, and heavy meromyosin.
Differential scanning calorimetry of the unfolding of myosin subfragment 1, subfragment 2, and heavy meromyosin.
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DOI：
10.1021/bi00462a018
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发表时间：
1990-03
期刊：
影响因子：
2.9
通讯作者：
J. Shriver;U. Kamath
中科院分区：
文献类型：
--
作者：
J. Shriver;U. Kamath
用差示扫描量热法（DSC）研究了兔骨骼肌重酶解肌球蛋白（HMM）及其亚片段1和亚片段2的热去折叠。在重肌球蛋白的DSC扫描中观察到两个不同的吸热峰。第一个吸热峰，在0.1 M KCl中pH 7.9时Tm为41 ℃，基于分离的亚片段2的扫描，将其归属于HMM的亚片段2结构域的解折叠。亚片段2结构域的展开在分离形式和HMM中都是可逆的。亚片段2在HMM中的解折叠可以拟合为具有161 kcal/mol的Δ Hvh和Δ Hcal的单个两态转变，表明亚片段2在HMM中作为单个结构域存在。亚片段2的解折叠的特征在于约30，000 cal/（deg.mol）的非常大的Δ Cp。在核苷酸的存在下，具有48摄氏度的Tm的高温HMM吸热移动到更高的温度，表明该峰对应于亚片段1结构域的解折叠。通过与分离的亚片段1的比较证实了这一分配。AMPPNP的稳定作用明显大于ADP。钒酸盐捕获的ADP物质比M.AMPPNP稍微更稳定，Tm为58 ℃。亚片段1的展开，无论是在孤立的形式和HMM中，是不可逆的。在HMM的亚片段1结构域和新鲜制备的亚片段1复合物的DSC扫描中仅注意到单个吸热。（250字处删节）
The thermal unfolding of rabbit skeletal heavy meromyosin (HMM), myosin subfragment 1, and subfragment 2 has been studied by differential scanning calorimetry (DSC). Two distinct endotherms are observed in the DSC scan of heavy meromyosin. The first endotherm, with a Tm of 41 degrees C at pH 7.9 in 0.1 M KCl, is assigned to the unfolding of the subfragment 2 domain of HMM based on scans of isolated subfragment 2. The unfolding of the subfragment 2 domain is reversible both in the isolated form and in HMM. The unfolding of subfragment 2 in HMM can be fit as a single two-state transition with a delta Hvh and delta Hcal of 161 kcal/mol, indicating that subfragment 2 exists as a single domain in HMM. The unfolding of subfragment 2 is characterized by an extraordinarily large delta Cp of approximately 30,000 cal/(deg.mol). In the presence of nucleotides, the high-temperature HMM endotherm with a Tm of 48 degrees C shifts to higher temperature, indicating that this peak corresponds to the unfolding of the subfragment 1 domain. This assignment has been confirmed by comparison with isolated subfragment 1. The stabilizing effect of AMPPNP was significantly greater than that of ADP. The vanadate-trapped ADP species was slightly more stable than M.AMPPNP with a Tm at 58 degrees C. The unfolding of subfragment 1, both in the isolated form and in HMM, was irreversible. Only a single endotherm was noted in the DSC scans of the subfragment 1 domain of HMM and in freshly prepared subfragment 1 complexes.(ABSTRACT TRUNCATED AT 250 WORDS)