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标题：Identification of a novel family of carbohydrate-binding modules with broad ligand specificity
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作者：Cheng-Jie Duan ; Yu-Liang Feng ; Qi-Long Cao 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2016
卷号：6
DOI：10.1038/srep19392
出版社：Springer Nature
摘要：Most enzymes that act on carbohydrates include non-catalytic carbohydrate-binding modules (CBMs) that recognize and target carbohydrates. CBMs bring their appended catalytic modules into close proximity with the target substrate and increase the hydrolytic rate of enzymes acting on insoluble substrates. We previously identified a novel CBM (CBM_C5614-1) at the C-terminus of endoglucanase C5614-1 from an uncultured microorganism present in buffalo rumen. In the present study, that the functional region of CBM_C5614-1 involved in ligand binding was localized to 134 amino acids. Two representative homologs of CBM_C5614-1, sharing the same ligand binding profile, targeted a range of β-linked polysaccharides that adopt very different conformations. Targeted substrates included soluble and insoluble cellulose, β-1,3/1,4-mixed linked glucans, xylan, and mannan. Mutagenesis revealed that three conserved aromatic residues (Trp-380, Tyr-411, and Trp-423) play an important role in ligand recognition and targeting. These results suggest that CBM_C5614-1 and its homologs form a novel CBM family (CBM72) with a broad ligand-binding specificity. CBM72 members can provide new insight into CBM-ligand interactions and may have potential in protein engineering and biocatalysis.