Kadler K E, Hojima Y, Prockop D J
Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
J Biol Chem. 1988 Jul 25;263(21):10517-23.
The effects of temperature on the assembly of collagen fibrils were examined in a system in which collagen monomers are generated de novo and in a physiological buffer by specific enzymic cleavage of type I pC-collagen, an intermediate in the normal processing of type I procollagen to type I collagen. Increasing the temperature of the reaction in the range of 29-35 degrees C decreased the turbidity lag and increased the rate of propagation as assayed by turbidity. The effect of temperature on the turbidity propagation rate gave a linear Arrhenius plot with a negative slope. The predicted value of the activation energy of propagation was 113 kJ/mol. However, the effects of temperature on the rate of assembly above 37 degrees C were opposite to the effects seen at temperatures below 37 degrees C. In the range of 37-41 degrees C, the turbidity propagation rate decreased markedly with temperature. Also, the turbidity lag increased. Therefore, much longer times were required for monomers to reach equilibrium with fibrils. A large fraction of the collagen monomers remaining in solution at temperatures above 37 degrees C was sensitive to rapid digestion by trypsin and alpha-chymotrypsin. Cooling the solutions to 25 degrees C made the monomers resistant to protease digestion. The results are consistent with the conclusion that, although formation of collagen fibrils is a classical example of an entropy-driven process of self-assembly, the rate of assembly between 37 and 41 degrees C is limited by reversible micro-unfolding of the monomer.
在一个系统中研究了温度对胶原纤维组装的影响，在该系统中，通过对I型前胶原正常加工为I型胶原过程中的中间体I型pC - 胶原进行特异性酶切，在生理缓冲液中从头生成胶原单体。在29 - 35摄氏度范围内升高反应温度，可缩短浊度滞后时间，并如通过浊度测定的那样增加传播速率。温度对浊度传播速率的影响给出了一条具有负斜率的线性阿伦尼乌斯图。传播活化能的预测值为113 kJ/mol。然而，温度对37摄氏度以上组装速率的影响与37摄氏度以下观察到的影响相反。在37 - 41摄氏度范围内，浊度传播速率随温度显著降低。而且，浊度滞后增加。因此，单体与纤维达到平衡需要更长的时间。在37摄氏度以上温度下留在溶液中的大部分胶原单体对胰蛋白酶和α - 糜蛋白酶的快速消化敏感。将溶液冷却至25摄氏度可使单体对蛋白酶消化具有抗性。这些结果与以下结论一致，即尽管胶原纤维的形成是熵驱动的自组装过程的经典例子，但在37至41摄氏度之间的组装速率受到单体可逆微展开的限制。
