权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Coarse Graining Methods for Studies of Structural Changes in Intermediate States of Membrane Proteins

研究膜蛋白中间态结构变化的粗粒度方法

基本信息

批准号：
11480188
负责人：
MITAKU Shigeki
金额：
$ 10.11万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

The function of a protein is expressed through the structural change or fluctuation. In this work, we studied experimentally and theoretically the mechanism of the structural change of membrane proteins, using bacteriorhodopsin as a model system of the membrane protein.We measured the denaturation behaviors of bacteriorhodopsin, a typical intrinsic membrane protein, changing the temperature and the light illumination conditions. At room temperature, the structure of bacteriorhodopsin recovered from photointermediate states to the ground state, while the recovery from the excited states was incomplete at the temperature around 50 ℃. We could conclude from extensive photobleaching experiments at various temperatures that the structure of bacteriorhodopsin is partly stabilized by polar loop segments which particularly contribute to the recovering process of the photocycle. Further experiments of the photobleaching at high temperature for mutated and chemically modified bacteriorhodopsin w … More ill lead to the physical mechanism of the photocycle.A novel method for theoretical structure prediction was developed on the basis of the preivious results of denaturation experiments. Supposing that seven transmembrane helices are continuum rods with the polarity distribution of their surfaces, we calculated the interaction energy of a seven-helix system. The positioning and orientation of seven helices could be predicted by minimizing the interaction energy. The most preferable configuration of helices was very similar to the actual structure of bacteriorhodopsin. In the framework of this method, the protonation and deprotonation of amino acid residues within the helical regions strongly affect the helix configuration. In fact, the calculation suggested that the positioning and the tilting of helices change during the photocycle in accordance with the structural analyzes of intermediate states of bacteriorhodopsin. The problem of the contribution of loop segments to the structural change should be solved for the understanding of the functioning mechanism. Less

蛋白质的功能是通过结构的变化或波动来表达的。本文以细菌视紫红质作为膜蛋白的模型系统，从实验和理论两方面研究了膜蛋白结构变化的机制。我们测量了细菌视紫红质（细菌视紫红质是一种典型的内在膜蛋白）在温度和光照条件下的变性行为。在室温下，细菌视紫红质的结构从光中间态恢复到基态，而在50℃左右的温度下，从激发态的恢复是不完全的。通过在不同温度下进行的大量光漂白实验，我们可以得出结论，细菌视紫红质的结构在一定程度上是由极性环段稳定的，这尤其有助于光循环的恢复过程。进一步对突变和化学修饰的细菌视紫红质进行高温光漂白实验，将进一步揭示光循环的物理机制。在前人变性实验结果的基础上，提出了一种新的理论结构预测方法。假设7个跨膜螺旋是具有表面极性分布的连续棒，我们计算了7螺旋体系的相互作用能。通过最小化相互作用能，可以预测七个螺旋的位置和方向。最理想的螺旋构型与细菌视紫红质的实际结构非常相似。在这种方法的框架内，螺旋区域内氨基酸残基的质子化和去质子化强烈影响螺旋构型。事实上，根据细菌视紫红质中间态的结构分析，计算表明螺旋的位置和倾斜在光循环过程中发生了变化。为了理解其作用机理，必须解决环段对结构变化的贡献问题。少