Effects of troponin on thermal unfolding of actin-bound tropomyosinстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация: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 53.8degreesC. Interaction with F-actin affects the character of thermal unfolding of Tin leading to appearance of a new Tm transition with maximum at about 48degreesC, but it has no influence on the thermal denaturation of F-actin stabilized by aluminum fluoride, which occurs within the temperature region above 70degreesC. Addition of troponin leads to significant increase in the cooperativity and enthalpy of the thermal transition of the actin-bound Tin. 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 100degreesC. 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.