DESIGN OF MOLECULAR INTEGRATED ELEMENTS BASED ON THE FLEXIBLE HIGHER ORDER STRUCTURE

为了建立完整分子系统的设计和构建原则，我们对生物分子系统的结构和工作设计进行了研究。本研究以动物脂肪酸合成酶和α-2-巨球蛋白为模型系统，两者都是功能元件完整的多功能巨蛋白。在脂肪酸合成酶的情况下，不同部分反应的七种酶被整合成具有明确目的的单一功能单元。当整合到两个活性中心中的七种酶在20 nm × 15 nm × 7 nm的有限空间内工作时，我们发现两个活性中心存在协同的触发器式运动。这样的运动可能是流体动力学耦合与溶剂粘度和波动的活性-粘度关系的实验结果清楚地表明。大规模整合蛋白质的结构域和亚基的粘度依赖性运动将容易地与整个反应的化学速率决定步骤耦合。发现蛋白质运动部分与添加到蛋白质水溶液中的粘原分子之间的流体动力学耦合强烈地依赖于粘原分子的大小。这一发现将在未来被用来估计蛋白质部分移动元素的大小。在α-2-巨球蛋白的大规模亚基重排中也表明了蛋白质运动与溶剂的类似流体动力学耦合。在本研究中，我们明确了集成系统的元素与溶剂之间的流体动力学耦合是在分子水平上设计集成系统时需要考虑的一个非常重要的因素。

With the aim to establish the designing and constructing principles of integrated molecular system, we studied the structure and working design of biological molecular systems. The model system of our work was animal fatty acid synthetase and alpha-2-macroglobuin, both are multi-functional giant proteins with integrated functional elements. In the case of fatty acid synthetase, seven-enzymes of different partial reactions are integrated into a single functional unit with a definite purpose. When the seven enzymes integrated into two active centers work in a limited space of 20nmxl5nmx7nm, we found that there is a concerted flip-flop type movement of two active centers. Such a movement is probably hydrodynamically coupled with the solvent viscosity and fluctuation as the experimental results on the activity-viscosity relationship clearly indicated. The viscosity dependent movement of the domains and subunits of integrated proteins in large scale will easily be coupled with the chemical rate determining step of the entire reaction. The hydrodynamic coupling between the moving parts of proteins and viscogen molecules added to the aqueous solution of protein was found to be acutely dependent on the size of viscogen. This finding will be exploited in future to estimate the size of the moving elements on the part of the proteins. Similar hydrodynamic coupling of protein movement with solvent is also indicated in the large scale subunit rearrangement of alpha-2- macroglobulin. In this study we made it clear that the hydrodynamic coupling between the elements of integrated system with the solvent is a very important factor to be considered in the design of integrated system on the molecular level.