Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, 20521 Turku, Finland.
Department of Mycology, Shandong Agricultural University, Taian, Shandong 271018, China.
Biochim Biophys Acta Proteins Proteom. 2017 Aug;1865(8):1030-1038. doi: 10.1016/j.bbapap.2017.05.002. Epub 2017 May 4.
Crystal structures of a β-1,3-glucanase from the thermophilic fungus Chaetomium thermophilum were determined at 1.20 and 1.42Å resolution in the free and glucose-bound form, respectively. This is the third structure of a family 55 glycoside hydrolase (GH55) member and the second from a fungus. Based on comparative structural studies and site-directed mutagenesis, Glu654 is proposed as the catalytic acid residue. The substrate binding cleft exhibits restricted access on one side, rendering the enzyme as an exo-β-1,3-glucanase as confirmed also by thin layer chromatography experiments. A lack of stacking interactions was found at the substrate binding cleft, suggesting that interactions at positions -1, +1 and +2 are sufficient to orientate the substrate. A binding pocket was identified that could explain binding of branched laminarin and accumulation of laminaritriose.
嗜热真菌嗜热毛壳菌β-1,3-葡聚糖酶的晶体结构分别在自由态和葡萄糖结合态下解析到 1.20 和 1.42Å 的分辨率。这是家族 55 糖苷水解酶（GH55）成员的第三个结构，也是第二个来自真菌的结构。基于比较结构研究和定点突变，推测 Glu654 为催化酸残基。底物结合裂隙的一侧呈现出受限的通道，使该酶成为外切-β-1,3-葡聚糖酶，这也通过薄层层析实验得到了证实。在底物结合裂隙处未发现堆积相互作用，表明在位置-1、+1 和+2 的相互作用足以定向底物。鉴定出一个结合口袋，可解释支链昆布多糖和昆布三糖的结合。
