Kremneva E V, Nikolaeva O P, Gusev N B, Levitsky D I
Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, 119071, Russia.
Biochemistry (Mosc). 2003 Jul;68(7):802-9. doi: 10.1023/a:1025043202615.
Differential scanning calorimetry (DSC) was used to study the effect of troponin (Tn) and its isolated components on the thermal unfolding of skeletal muscle tropomyosin (Tm) bound to F-actin. It is shown that in the absence of actin the thermal unfolding of Tm is expressed in two well-distinguished thermal transitions with maxima at 42.8 and 53.8 degrees C. Interaction with F-actin affects the character of thermal unfolding of Tm leading to appearance of a new Tm transition with maximum at about 48 degrees C, but it has no influence on the thermal denaturation of F-actin stabilized by aluminum fluoride, which occurs within the temperature region above 70 degrees C. Addition of troponin leads to significant increase in the cooperativity and enthalpy of the thermal transition of the actin-bound Tm. The most pronounced effect of Tn was observed in the absence of calcium. To elucidate how troponin complex affects the properties of Tm, we studied the influence of its isolated components, troponin I (TnI) and troponin T (TnT), on the thermal unfolding of actin-bound Tm. Isolated TnT and TnI do not demonstrate cooperative thermal transitions on heating up to 100 degrees C. However, addition of TnI, and especially of TnT, to the F-actin-Tm complex significantly increased the cooperativity of the thermal unfolding of actin-bound tropomyosin.
差示扫描量热法（DSC）用于研究肌钙蛋白（Tn）及其分离组分对与F-肌动蛋白结合的骨骼肌原肌球蛋白（Tm）热解折叠的影响。结果表明，在没有肌动蛋白的情况下，Tm的热解折叠表现为两个明显区分的热转变，最大值分别在42.8和53.8摄氏度。与F-肌动蛋白的相互作用影响Tm热解折叠的特征，导致出现一个新的Tm转变，最大值约在48摄氏度，但对由氟化铝稳定的F-肌动蛋白的热变性没有影响，F-肌动蛋白的热变性发生在70摄氏度以上的温度区域。添加肌钙蛋白会导致与肌动蛋白结合的Tm热转变的协同性和焓显著增加。在没有钙的情况下观察到Tn的最显著效果。为了阐明肌钙蛋白复合物如何影响Tm的性质，我们研究了其分离组分肌钙蛋白I（TnI）和肌钙蛋白T（TnT）对与肌动蛋白结合的Tm热解折叠的影响。分离的TnT和TnI在加热至100摄氏度时未表现出协同热转变。然而，向F-肌动蛋白-Tm复合物中添加TnI，尤其是TnT，显著增加了与肌动蛋白结合的原肌球蛋白热解折叠的协同性。
