Calorimetric evaluation of the existence of separate domains in bovine prothrombin.
Calorimetric evaluation of the existence of separate domains in bovine prothrombin.
复制标题
牛凝血酶原中单独结构域的存在的量热评估。
DOI：
10.1021/bi00504a003
复制
发表时间：
1981
期刊：
影响因子：
2.9
通讯作者：
Castellino,FJ
中科院分区：
文献类型：
--
作者：
Ploplis,VA;Strickland,DK;Castellino,FJ
Victoria A. Ploplis,* Dudley K. Strickland, § and Francis J. Castellino* abstract: At least two endothermal (denaturing) transitions, at 53.1 ą 1.5 C and 58.2 ą 1.5 C, of a total AH of 324 ą 12 kcal mol'1, are observed, by differential scanning calori-metry (DSC), for solutions of bovine prothrombin. Studies with the appropriate isolated fragments show that the lowtemperature transition arises from the prethrombin 1 portion of the molecule and the higher temperature transitionorigi-nates from the fragment 1 region. We have compared the transition temperature midpoints, Tm, the total AH values of the thermal transitions, and the ratio of the calorimetric to van’t Hoff enthalpies of these isolated regions of prothrombin with those of the prothrombin molecule. The data obtained strongly suggest that they exist as independent domains in the intact bovine prothrombin molecule. On the other hand, when prethrombin 1 is digested to fragment 2 and prethrombin 2, DSC experiments performed on the isolated components, in the presence or absence of Ca2+, strongly support the con-clusion that these regions contribute in a cooperative fashion to the structure of intact prethrombin 1(and prothrombin). Addition of saturating (5 mM) levels of Ca2+ to intact bovine prothrombin results in essentially no change in the Tm of the prethrombin 1 domain, an increase in the Tm of the fragment 1 domain, and a decrease in the total AH of the thermal transitions. Further, the endotherm for the prethrombin 1 region is markedly sharpened in the presence of Ca2+. Ad-dition of Ca2+ causes no alteration in the Tm of 52.6 ą 1.5 C or the AH of 200 ą 10 kcal mol" 1 of isolated prethrombin 1, and the sharpening effect induced by Ca2+ in the prethrombin1 region of bovine prothrombin was not observed with isolated prethrombin 1. The Tm of the fragment 1 region of intact bovine prothrombin is increased to 64.8 ą 1.5 C upon addition of 5 mM Ca2+ to the solution. Similar changes are also noted in isolated fragment 1 as a result of addition of Ca2+. Here, the Tm of fragment 1 of 58.5 ą 1.5 C and the AH of fragment1 of 134 ą 10 kcal mol'1 are altered to 64.5 ą 1.5 C and 102 ą 10 kcal mol'1, respectively, as a result of addition of 5 mM
