绿豆胰蛋白酶抑制剂┐猪胰蛋白酶复合物的四方晶体结构  

Tetragonal Crystal Structure of Mung Bean Inhibitorporcine Trypsin Complex

作　　者：刘小舟[1,2] 刘博 卢光莹 卫新成 华子千 戚正武[1,2] 

机构地区：[1]北京大学生命科学学院蛋白质工程及植物基因工程国家重点实验室 [2]中国科学院上海生物化学研究所

出　　处：《生物化学与生物物理学报》1998年第4期357-362,共6页

摘　　要：本文报道了绿豆胰蛋白酶抑制剂－猪胰蛋白酶（１∶２）复合物的四方晶体的结构测定。晶体属于Ｉ４２２空间群，衍射分辨率为０．２５ｎｍ，共确定了绿豆抑制剂５６个残基的空间位置。与已报道的三方晶体结构相比，其中的抑制剂分子的结构基本相同，并且抑制剂－酶三元复合物在四方晶体中也处于堆积无序状态，即复合物按两种取向进行堆积：Ｔａ∶ＭａＭｂ∶Ｔｂ和Ｔｂ∶ＭｂＭａ∶Ｔａ（Ｔａ，Ｔｂ为胰蛋白酶，Ｍａ为抑制剂结合环Ⅰ，Ｍｂ为抑制剂结合环Ⅱ）。但四方晶体结构比三方晶体结构多测定了一个抑制剂残基Ｐｒｏ１１的位置，同时，四方晶体中的抑制剂不存在膺β－折叠片层结构，其构象与三方晶体中的抑制剂相比有所变化。分析表明抑制剂的两个刚性的结构域之间的连接肽具有一定的柔性，并因此形成不同的晶型。此外，绿豆抑制剂与其他Ｂｏｗｍａｎ－Ｂｉｒｋ抑制剂相比。Crystal structure of the mung bean inhibitorporcine trypsin (1∶2) ternary complex in the tetragonal crystal with space group I422 was determined at 0.25 nm resolution. 56 residues of the mung bean inhibitor were resolved among which one more residue Pro11 was determined than the previously reported structure in the trigonal crystal of the same complex. The structure of the inhibitor in the tetragonal crystal is similar to that in the trigonal crystal and the complexes in tetragonal crystal is also in packing disorder as in trigonal crystal, i.e., the complexes pack in two orientations Ta∶MaMb∶Tb and Tb∶MbMa∶Ta (Ta, Tb=trypsin, Ma, Mb=loopⅠand loopⅡof mung bean inhibitor respectively). But there are some differences in the two crystal forms. First, the inhibitor in the tetragonal crystal has no pseudoβsheet structure which the trigonal crystal has. Second, its conformation is somewhat different from that in the trigonal crystal. Analysis showed that the linkage peptides between the two rigid domains of the inhibitor were flexible, which also accounted for the formation of different crystal forms of this complex. Moreover, comparing mung bean inhibitor to other BowmanBirk inhibitors showed that the two doublestranded antiparallel βsheets and the reactive binding loops were highly conservative.

关 键 词：猪胰蛋白酶 复合地 晶体结构 MBI 

分 类 号：Q556.3[生物学—生物化学]