二甲基砷酸盐缓冲剂在蛋白质晶体学中新应用的研究

项目名称： 二甲基砷酸盐缓冲剂在蛋白质晶体学中新应用的研究

项目编号： No.31200641

项目类型： 青年科学基金项目

立项/批准年度： 2013

项目学科： 生物物理、生化与生物分子学、生物力学与组织工程

项目作者： 刘祥

作者单位： 天津市国际生物医药联合研究院

项目金额： 23万元

中文摘要： 二甲基砷酸盐作为蛋白质纯化和结晶的缓冲溶液得到广泛使用，而其它方面的特点则很少被触及。蛋白质结构数据库（PDB）中的统计值显示，有近3500个蛋白质的结晶条件中使用了二甲基砷酸盐，超过200个结构模型中包含了二甲基砷酸盐，其中67个结构中二甲基砷酸盐与蛋白表面的半胱氨酸以共价键形式相结合。 这些统计数字说明二甲基砷酸盐存在着作为蛋白质表面半胱氨酸的共价修饰的潜在可能，特别是其中含有的砷元素对于蛋白质晶体学结构解析有着更为特殊的意义。 与砷元素同一周期的硒元素可以通过硒代甲硫氨酸的方式被引入到蛋白质结晶学中，成为蛋白质结构解析最重要和最广泛的反常信号来源。砷元素与硒元素反常信号的特征相似，并可以通过共价修饰半胱氨酸方式很容易地被引入蛋白质中，这使得二甲基砷酸盐具有通过反常散射信号解析蛋白质晶体相位的潜力。 希望通过此项研究实现二甲基砷酸盐特异性修饰在蛋白质晶体数据解析中发挥作用。

中文关键词： 砷元素；二甲基砷；蛋白质结晶；氯二甲基亚砷；基质金属蛋白酶

英文摘要： Although cacodylic buffer is widely used in protein purification and crystallization, people have not paid much attention to its other functions during research. In fact, according to statistics in Protein Data Bank (PDB), nearly 3500 protein structure entries have cacodylic buffer in their crystallization conditions, and over 200 models have located cacodylic coordinates in their structures. More importantly, in 67 PDB entries cacodylic acid molecules were covalently bound to cysteines on protein surface. All these data proved that the cacodylic buffer would be a potential candidate in protein structure determination. The most powerful method in de novo protein structure determination is using anomalous signal generated by Se-Methionines (Se-Mets), which were genetically incorporated into protein. In contrast, arsenic, the potential anomalous scattering factor, was overlooked for a long time. Actually, arsenic locates besides selenium in the periodic table and they shared similar f prime and f double prime in their own absorption edge (Theoretically the absorption edge of As is about 1.04?, while Se is about 0.98?). It is very convenient to collect arsenic anomalous signal in a Se-dedicated synchrotron beamline. The modification of cacodylic buffer on cysteines could be an important way to incorporate a

英文关键词： arsenic；cacodylic acid；protein crystallization；dimethylchloroarsine；matrix metalloproteinases