DIRECT ENTHALPY MEASUREMENTS OF FACTOR-X AND PROTHROMBIN ASSOCIATION WITH SMALL AND LARGE UNILAMELLAR VESICLES
DIRECT ENTHALPY MEASUREMENTS OF FACTOR-X AND PROTHROMBIN ASSOCIATION WITH SMALL AND LARGE UNILAMELLAR VESICLES
复制标题
DOI：
10.1021/bi00188a033
复制
发表时间：
1994-06-07
期刊：
影响因子：
2.9
通讯作者：
NELSESTUEN, GL
中科院分区：
文献类型：
--
作者：
PLAGER, DA;NELSESTUEN, GL
采用等温滴定量热法测定钙依赖性蛋白构象变化及随后凝血因子X和凝血酶原与磷脂囊泡相互作用的焓。还确定了囊泡大小的影响。蛋白构象变化伴随因子X和凝血酶原分别为-12 +/- 1和-7 ~ -15 kcal/mol。凝血酶原值的范围是由使用不同的蛋白质制剂引起的，可能是由于这种蛋白质的不理想行为；当加入钙的时候。X因子和凝血酶原与磷脂酰丝氨酸(PS)/磷脂酰胆碱（PC）大单层囊泡（LUVs，直径120 nm）的表观结合焓（Delta H-assoc）接近0 kcal/mol，而与PS/PC小单层囊泡（SUVs，直径40 nm）的表观结合焓（Delta H-assoc）分别为-9 +/- 3和-7 +/- 2 kcal/mol。这种差异似乎与钙与这些囊泡结合的δ h相辅相成。也就是说，钙与suv的相互作用是热的，与luv的相互作用是放热的。虽然这些性质可能表明钙与luv结合的程度与suv有相当大的差异，但通过平衡透析检测到suv和luv结合的钙量几乎没有差异。无论如何，结果表明蛋白质与luv的结合主要是熵驱动的，而与suv的结合主要是焓驱动的。钙依赖因子X或凝血酶原与suv结合的放热过程可能是由蛋白质诱导的磷脂包装/钙相互作用的变化引起的，可能与钙与磷脂结合方式的变化有关。
Isothermal titration calorimetry was used to determine the enthalpy for the calcium-dependent protein conformation change and subsequent interaction of blood clotting factor X and prothrombin with phospholipid vesicles. The effect of vesicle size was also determined. The protein conformation change was accompanied by -12 +/- 1 and -7 to -15 kcal/mol for factor X and prothrombin, respectively. The range of values for prothrombin arose from use of different protein preparations and may be due to non-ideal behavior of this protein;when calcium was added. The apparent enthalpy of association (Delta H-assoc) of both factor X and prothrombin with phosphatidylserine (PS)/phosphatidylcholine (PC) large unilamellar vesicles (LUVs, 120 nm diameter) was shown to be near 0 kcal/mol In comparison, Delta H-assoc for interaction with PS/PC small unilamellar vesicles (SUVs; 40 nm diameter) was -9 +/- 3 and -7 +/- 2 kcal/mol for factor X and prothrombin, respectively. This difference appeared complementary to Delta H-assoc for calcium binding to these vesicles. That is, the interaction of calcium was athermic with SUVs and exothermic with LUVs. While such properties might suggest a considerable difference in the mariner: of calcium binding to LUVs versus SUVs, little difference in the quantity of calcium bound to SUVs and LUVs was detected by equilibrium dialysis. In any event, the results indicate that protein binding to LUVs was primarily entropy driven whereas binding to SUVs was primarily enthalpy driven. The exothermic process for calcium-dependent factor X or prothrombin binding to SUVs may result from protein-induced changes in the phospholipid packing/calcium interaction, possibly related to changes in how calcium is bound to the phospholipid.