江浙蝮蛇毒碱性磷脂酶A_2新单斜晶型晶体结构测定  

Structure Determination of Basic Phospholipase A_2 from the Venom of Agkistrodon halys Pallas in A New Monoclinic Crystal Form

作　　者：赵克浩[1] 柴笑梅 宋时英[1] 林政炯[1] 周元聪[2] 

机构地区：[1]中国科学院生物物理研究所生物大分子国家重点实验室,北京100101 [2]中国科学院上海生物化学研究所,上海200031

出　　处：《生物化学与生物物理学报》2001年第4期409-414,共6页

基　　金：中国科学院重大项目资助 (KJ 95 1 A1 6 0 1)&&

摘　　要：江浙蝮蛇毒碱性磷脂酶A2 具有溶血和抗凝血活性。在不含正辛基吡喃葡糖苷 (n octylβ o glucopyra noside ,简称 β OG)结晶条件下 ,培养出该酶新单斜晶型晶体。采用X射线晶体学方法 ,成功地解出了不对称单位含 4个分子的新单斜晶型结构。在分子置换研究中运用自身与交叉旋转函数的联合分析 ,在结构修正中使用非晶体学对称性制约 ,最终结构模型具有可接受的晶体学R因子和合理的立体化学参数。与已报道的结合 β OG的单斜晶型结构类似 ,新晶型中分子也形成具有二重对称性的、被界面识别部位连接的二体 ,两个二体再通过非晶体学二重轴联系形成一个赝 2 2 2对称的四聚体。结晶条件改变对四体在晶胞中的堆砌产生重要影响 ,导致晶胞参数的显著变化 ,然而对二体和四体本身影响较小 。Basic phospholipase A 2 from the venom of Agkistrodon halys Pallas ( Agkistrodin blomhoffii brevicaudus) exhibits hemolytic and anti coagulant activities. A new monoclinic crystal form with four molecules per asymmetric unit was grown in the absence of n octyl β o glucopyranoside (β OG). The enzyme structure was determined by the molecular replacement method. The combined analysis of self and cross rotation function was used and non crystallographic symmetry restraints were imposed to the structure refinement. The final model gave an acceptable crystallographic R factor and reasonable stereochemistry. Two molecules formed an interfacial recognition site linked dimer and two such dimers constituted a tetramer having pseudo 222 symmetry. Structural comparison with previously reported monoclinic forms, in which β OG was bound, showed that the variation of crystallization conditions had effects on the crystal packing, leading to significant changes of the cell parameters. Nevertheless, the structures of both the dimer and tetramer in the two crystal forms closely resembled to each other, indicating that the oligomers found in the monoclinic crystal forms were stable.

关 键 词：蛇毒磷酯酶A2 X射线晶体学 三维结构 寡聚体 

分 类 号：Q55[生物学—生物化学]