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首页> 外文期刊>Journal of Molecular Biology >CRYSTAL STRUCTURE OF THE ASPARTIC PROTEINASE FROM RHIZOMUCOR MIEHEI AT 2.15 ANGSTROM RESOLUTION
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CRYSTAL STRUCTURE OF THE ASPARTIC PROTEINASE FROM RHIZOMUCOR MIEHEI AT 2.15 ANGSTROM RESOLUTION

机译：米氏根瘤菌在2.15埃分辨率下天冬氨酸蛋白酶的晶体结构

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摘要

The crystal structure of the aspartic proteinase from Rhizomucor miehei (RMP, EC 3. 4. 23. 23) has been refined to 2.15 Angstrom resolution to a crystallographic R-value of 0.215 and an R-free of 0.281. The root-mean-square (r.m.s.) error for the atomic coordinates estimated from a Luzzati plot is 0.2 Angstrom. The r.m.s. deviations for the bond distances and bond angles from ideality are 0.01 Angstrom and 1.7 degrees, respectively. RMP contains two domains that consist predominantly of beta-sheets. A large substrate-binding cleft is clearly visible between the two domains, and the two catalytic residues Asp38 and Asp237 are located in the middle of the cleft with a water molecule bridging the carboxyl groups of Asp38 and Asp237. Due to crystal packing, the C-terminal domain is more mobile than the N-terminal domain. Most of the aspartic proteinases (except renin) reach their maximum activity at acidic pH. We propose that the optimum pH of each aspartic proteinase is determined by the electrostatic potential at the active site, which, in turn, is determined by the positions and orientations of all the residues near the active site. RMP is the most glycosylated among the aspartic proteinases. The carbohydrate moieties are Linked to Asn79 and Asn188. Asn79 is in the middle of a beta-strand and Asn188 is on a surface loop in contrast to the previous hypothesis proposed by Brown and Yada that they are both on surface beta-turns. RMP has a very high thermal stability. The high thermal stability is probably due to the high level of glycosylation. We propose that the highly flexible carbohydrates act as heat reservoirs to stabilize the conformation of RMP and therefore give the enzyme a high level of thermal stability. Three-dimensional structural and sequence alignments of RMP with other aspartic proteinases show that RMP is most structurally homologous to that of Mucor pusillus (MPP), and differs from other fungal enzymes as much as it does from the mammalian enzymes. This suggests that RMP and MPP diverged from the main stream of aspartic proteinases at an early stage of evolution. The present study adds a second member to this subfamily of aspartic proteinases. (C) 1997 Academic Press Limited. [References: 50]
机译：来自Rhizomucor miehei（RMP，EC 3. 4. 23. 23）的天冬氨酸蛋白酶的晶体结构已被精制至2.15埃分辨率，晶体学R值为0.215，无R值为0.281。根据Luzzati图估算的原子坐标的均方根（r.m.s.）误差为0.2埃。 r.m.s.键距和键角与理想度的偏差分别为0.01埃和1.7度。 RMP包含两个域，主要由β-sheets组成。在两个结构域之间清晰可见大的底物结合裂隙，两个催化残基Asp38和Asp237位于裂隙的中间，水分子桥接了Asp38和Asp237的羧基。由于晶体堆积，C端结构域比N端结构域更具流动性。大多数天冬氨酸蛋白酶（肾素除外）在酸性pH值下均达到最大活性。我们建议，每种天冬氨酸蛋白酶的最佳pH值取决于活性位点的静电势，而静电势又取决于活性位点附近所有残基的位置和方向。 RMP是天冬氨酸蛋白酶中糖基化程度最高的。碳水化合物部分连接至Asn79和Asn188。与Brown和Yada先前提出的两者都在表面β转角上的假设相反，Asn79在β链中间，而Asn188在表面环上。 RMP具有很高的热稳定性。高的热稳定性可能是由于高水平的糖基化。我们建议高度灵活的碳水化合物充当热库来稳定RMP的构象，因此赋予酶高水平的热稳定性。 RMP与其他天冬氨酸蛋白酶的三维结构和序列比对表明，RMP在结构上与Mucor pusillus（MPP）最为同源，并且与其他真菌酶的区别与哺乳动物酶的不同。这表明在进化的早期，RMP和MPP与天冬氨酸蛋白酶的主流分开了。本研究为该天冬氨酸蛋白酶亚家族增加了第二个成员。 （C）1997 Academic Press Limited。 [参考：50]

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