Departamento de Física, Instituto de Ciências Exatas, Naturais e Educação, Universidade Federal do Triângulo Mineiro, Av. Frei Paulino, 30 - Bairro Abadia Uberaba, MG 38025-180, Brazil.
Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador Sãocarlense, 400, São Carlos SP 13566-590, Brazil.
Biochim Biophys Acta Gen Subj. 2019 Jun;1863(6):1015-1026. doi: 10.1016/j.bbagen.2019.03.013. Epub 2019 Mar 19.
Cellulases from glycoside hydrolase family 7 (GH7) play crucial roles in plant lignocellulose deconstruction by fungi, but structural information available for GH7 fungal endoglucanases is limited when compared to the number of known sequences in the family. Here, we report the X-ray structure of the glycosylated catalytic domain (CD) of Trichoderma harzianum endoglucanase, ThCel7B, solved and refined at 2.9 Å resolution. Additionally, our extensive molecular dynamics simulations of this enzyme in complex with a variety of oligosaccharides provide a better understanding of its promiscuous hydrolytic activities on plant cell wall polysaccharides. The simulations demonstrate the importance of the hydrogen bond between substrate O2 hydroxyl in the subsite -1 and a side chain of catalytic Glu196 which renders ThCel7B capable to catalytically cleave cello and xylooligosaccharides, but not mannooligosaccharides. Moreover, detailed structural analyses and MD simulations revealed an additional binding pocket, suitable for accommodation of oligosaccharide decorations and/or substrates with mixed glycoside bonds that abuts onto the binding cleft close to subsite +2.
糖苷水解酶家族 7（GH7）的纤维素酶在真菌对植物木质纤维素的解构中起着至关重要的作用，但与该家族中已知序列的数量相比，可用的 GH7 真菌内切葡聚糖酶的结构信息有限。在这里，我们报告了哈茨木霉内切葡聚糖酶 ThCel7B 的糖基化催化结构域（CD）的 X 射线结构，其分辨率为 2.9Å。此外，我们对该酶与各种寡糖的广泛分子动力学模拟提供了对其在植物细胞壁多糖上的混杂水解活性的更好理解。模拟表明，在底物 -1 位的 O2 羟基和催化 Glu196 的侧链之间形成氢键的重要性，使 ThCel7B 能够催化切割纤维二糖和木二糖，但不能切割甘露寡糖。此外，详细的结构分析和 MD 模拟揭示了一个额外的结合口袋，适合容纳寡糖修饰物和/或具有混合糖苷键的底物，该口袋与靠近 +2 位的结合裂隙相邻。
