自然界中的演化过程,是不断的适应环境的变化,在微妙的差异中,慢慢的发展出方向,因此演化的变化确实存在,但也需历经长久的变化,而一份由美国亚历桑那州立大学 (Arizona State University) 生物设计研究所(Biodesign Institute) John Chaput 博士所主导的研究计划,就在实验室中,尝试着模拟达尔文的演化论,设计出自然界中,要历经三十亿年才能演化出来的蛋白质。
据参与的科学家发表在最新一期 PLoS ONE期刊的论文显示,研究这个题目的目的,除了能够回答许多蛋白质演化的基本问题外,还希望能够因着了解蛋白质演化的关键,设计出具有特殊功能,现代未曾出现的蛋白质,这样的蛋白质,不但具有生物产业上应用的价值,还可以开发新一代的药物。
研究人员在设计的演化过程中,以二十个氨基酸的组合排列,架构出难以数计的蛋白质序列,然而这些序列不见的能够存在于自然界中,最有可能的因素,就是因为结构的不稳定 或是功能的不重要性,往往逃不过模拟演化的过程 研究人员从经验中,慢慢缩小目标 最后选择以黏附ATP的蛋白分子 大小约在 80个氨基酸左右,的蛋白颗粒为目标,并且进一步的利用 3D结晶学的技术,分析最稳定的结构可能,结果研究人员确实发现有两个特殊的氨基酸,具有加强黏着力 易溶于水以及高耐热性的特质,很容易在演化的筛选中存活下来。
科学家表示下一个目标,就是利用这样的一个模拟经验,帮助设计具有治疗作用的功能性蛋白质。
原始出处:
PLoS ONE
Received: March 28, 2007; Accepted: April 25, 2007; Published: May 23, 2007
Structural Insights into the Evolution of a Non-Biological Protein: Importance of Surface Residues in Protein Fold Optimization
Matthew D. Smith1,2, Matthew A. Rosenow1,2, Meitian Wang2, James P. Allen2, Jack W. Szostak3, John C. Chaput1,2*
1 Center for BioOptical Nanotechnology, The Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America, 2 Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States of America, 3 Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
Phylogenetic profiling of amino acid substitution patterns in proteins has led many to conclude that most structural information is carried by interior core residues that are solvent inaccessible. This conclusion is based on the observation that buried residues generally tolerate only conserved sequence changes, while surface residues allow more diverse chemical substitutions. This notion is now changing as it has become apparent that both core and surface residues play important roles in protein folding and stability. Unfortunately, the ability to identify specific mutations that will lead to enhanced stability remains a challenging problem. Here we discuss two mutations that emerged from an in vitro selection experiment designed to improve the folding stability of a non-biological ATP binding protein. These mutations alter two solvent accessible residues, and dramatically enhance the expression, solubility, thermal stability, and ligand binding affinity of the protein. The significance of both mutations was investigated individually and together, and the X-ray crystal structures of the parent sequence and double mutant protein were solved to a resolution limit of 2.8 and 1.65 Å, respectively. Comparative structural analysis of the evolved protein to proteins found in nature reveals that our non-biological protein evolved certain structural features shared by many thermophilic proteins. This experimental result suggests that protein fold optimization by in vitro selection offers a viable approach to generating stable variants of many naturally occurring proteins whose structures and functions are otherwise difficult to study.