Structural Insight of a Trimodular Halophilic Cellulase with a Family 46 Carbohydrate-Binding Module.
Structural Insight of a Trimodular Halophilic Cellulase with a Family 46 Carbohydrate-Binding Module.
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具有 46 族碳水化合物结合模块的三模块嗜盐纤维素酶的结构洞察。
DOI：
10.1371/journal.pone.0142107
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Ma Y
中科院分区：
文献类型：
--
作者：
Zhang H;Zhang G;Yao C;Junaid M;Lu Z;Zhang H;Ma Y
纤维素酶是生物燃料工业中使用的关键酶。典型的纤维素酶含有通过柔性接头连接至碳水化合物结合模块（CBM）的催化结构域。在这里，我们报道了一种非典型三模块化纤维素酶的结构，该酶具有催化结构域、CBM46 结构域和它们之间的刚性 CBM_X 结构域。催化结构域显示出GH5家族的特征，而CBM46结构域具有三明治样结构。催化结构域和 CBM46 结构域形成延伸的底物结合裂口，其中几个色氨酸残基充分暴露。诱变测定表明这些残基对于酶活性至关重要。凝胶亲和电泳表明这些色氨酸残基参与多糖底物结合。此外，静电势分析表明，CelB 的几乎整个溶剂可及表面都带负电，这与该酶的嗜盐性质一致。
Cellulases are the key enzymes used in the biofuel industry. A typical cellulase contains a catalytic domain connected to a carbohydrate-binding module (CBM) through a flexible linker. Here we report the structure of an atypical trimodular cellulase which harbors a catalytic domain, a CBM46 domain and a rigid CBM_X domain between them. The catalytic domain shows the features of GH5 family, while the CBM46 domain has a sandwich-like structure. The catalytic domain and the CBM46 domain form an extended substrate binding cleft, within which several tryptophan residues are well exposed. Mutagenesis assays indicate that these residues are essential for the enzymatic activities. Gel affinity electrophoresis shows that these tryptophan residues are involved in the polysaccharide substrate binding. Also, electrostatic potential analysis indicates that almost the entire solvent accessible surface of CelB is negatively charged, which is consistent with the halophilic nature of this enzyme.