别构酶ATCase与底物分子协同结合过程的构象变化特性

The Features of the Conformational Changes During the Cooperative Interaction of ATCase with Substrates

利用可描述协同结合特性的动力学方法,得到了反映单个别构酶ATCase分子的结合分数与底物浓度之间的关系式.表明在确定的底物浓度条件下,单个别构酶ATCase分子处于确定的构象态,随着底物浓度的增加,别构酶ATCase分子将经历一系列中间态达到饱和构象态,S型结合分数曲线实际上显示了单个别构酶ATCase分子与底物分子的协同结合特性.利用所得模型分析了调节物分子对底物协同结合过程的影响,合理解释了结合分数曲线随调节物浓度变化而发生改变的实验结果,与别构酶ATCase分子具有的结构及所产生的生物学功能是自给的.

On the basis of analyzing the features of the interaction between ATCase and specific substrates, the process of the interaction of an ATCase with substrates can be treated as a cooperative reversible binding one. The curve of the fractional saturation of ATCase versus the substrate concentrations can be obtained by means of kinetic methods. It shows that an ATCase molecule in the constant substrate concentration is at a fixed conformational state. The conformation for an ATCase molecule undergoes a series of the intermediately conformational states from the form without bound substrate to saturated one as substrate concentrations increase. The S-shaped curve of fractional saturation for ATCase actually represents the real cooperatively interactive effect that occurs in an ATCase molecule as substrates are bound. The effect of regulatory molecule on the cooperative process of substrate binding has been investigated by using the above model.The results explained the fout which has been experimentally found that the curve of the fractional saturation for ATCase can shift with the change in substrate concentrations.The above conclusions are self-consistent with molecular structure of and biological function of ATCase.