How the N-terminal xylan-binding domain from C.fimi xylanase D recognises xylan

摘要

Plant cell walls are complex structures, and their function requires them to be strong and resistant to degradation. The structural core of the cell wall is the microfibril, which is made of cellulose (Figure 1a) and is considered to be reasonably crystalline, although with amorphous regions. The microfibrils are crosslinked together by lignin and by a mesh of polysaccharide strands known collectively as hemicelluloses, and consisting of xylans, arabinans and mannans. In contrast to the cellulose microfibrils, hemicellulose is amorphous and often consist of single or weakly associated strands rather than the crystallien bundles of strands seen in microfibrils. Xylan is a polymer of xylose, which is similar to glucose but lacks the C_6 carbon (Figure 1b). In contrast to cellulose, hemicelluloses are often structurally heterogeneous. For example, xylans may be quite heavily derivatised by acetylation or glycosylation. The degree and nature of derivatisation is species-specific.