Structural studies of a two-domain chitinase from Streptomyces griseus HUT6037
Structural studies of a two-domain chitinase from Streptomyces griseus HUT6037
复制标题
DOI：
10.1016/j.jmb.2006.02.013
复制
发表时间：
2006-04-28
影响因子：
5.6
通讯作者：
Nonaka, T
中科院分区：
文献类型：
--
作者：
Kezuka, Y;Ohishi, M;Nonaka, T
几丁质酶C（Chitinase C，ChiC）是第一个在非高等植物中发现的糖苷水解酶家族19几丁质酶。通过接头肽连接的N-末端几丁质结合结构域和C-末端催化结构域构成ChiC。我们确定了全长ChiC的晶体结构，这是该家族中两个结构域几丁质酶的唯一代表。催化结构域具有富含α-螺旋的折叠，并具有包含催化位点的深裂缝，并且与植物几丁质酶的催化结构域相比，结构域表面上缺少三个环。几丁质结合结构域是一种全β蛋白，其表面上排列着两个色氨酸残基（Trp 59和Trp 60）。我们建议的结合机制的三-N-乙酰壳三糖到几丁质结合域的分子动力学（MID）模拟的基础上。在这种机制中，配体分子通过两个堆积相互作用和两个氢键很好地结合在表面暴露的结合位点上，并且只有Trp 59和Trp 60参与结合。此外，Trp 60侧链的灵活性，这可能涉及调整结合表面，以适应表面的结晶甲壳素的卡方2角的旋转，显示。(c)2006爱思唯尔有限公司保留所有权利。
Chitinase C (ChiC) from Streptomyces griseus HUT6037 was the first glycoside hydrolase family 19 chitinase that was found in an organism other than higher plants. An N-terminal chitin-binding domain and a C-terminal catalytic domain connected by a linker peptide constitute ChiC. We determined the crystal structure of full-length ChiC, which is the only representative of the two-domain chitinases in the family. The catalytic domain has an alpha-helix-rich fold with a deep cleft containing a catalytic site, and lacks three loops on the domain surface compared with the catalytic domain of plant chitinases. The chitin-binding domain is an all-beta protein with two tryptophan residues (Trp59 and Trp60) aligned on the surface. We suggest the binding mechanism of tri-N-acetylchitotriose onto the chitin-binding domain on the basis of molecular dynamics (MID) simulations. In this mechanism, the ligand molecule binds well on the surface-exposed binding site through two stacking interactions and two hydrogen bonds and only Trp59 and Trp60 are involved in the binding. Furthermore, the flexibility of the Trp60 side-chain, which may be involved in adjusting the binding surface to fit the surface of crystalline chitin by the rotation of chi 2 angle, is shown. (c) 2006 Elsevier Ltd. All rights reserved.