In both plants and bacteria, a number of cellulose synthase (CesA)/ cellulose synthase-like (Csl) proteins from the glycosyltransferase family 2 (GT2) have been identified that synthesize different classes of β-glucans. These proteins can synthesize solely (1,3)-β-linkages to produce curdlan, (1,4)-β-glucosidic linkages to produce cellulose, or a combination of the two linkages to produce mixed-linkage β-glucans (MLGs). The availability of a crystal structure for a bacterial CesA has allowed for an understanding of which residues are vital for the transfer of a glucose sugar to a glucan chain, yet it is not clear which residues are critical for the formation of specific linkages. To explore the specificity of these GT2 proteins we have utilised: 1) sequence and phylogenetic analyses to identify the conservation status of residues across all types of Csl proteins, 2) homology modelling to produce a model of a curdlan synthase (CrdS) using the CesA crystal structure as a template, and 3) molecular dynamics (MD) in order to identify residues that have key interactions between the trans-membrane channel of both the BcsA crystal structure and the CrdS homology model, and their natural β-glucan products. Motifs critical to the specific activities were found in certain secondary structures, with these regions and specific residues now the focus of experimental approaches in which mutated forms are heterologously expressed and their catalytic activities determined.

Modelling the structure and dynamics of bacterial cellulose synthase-like proteins to identify motifs critical for their specific functions

256th National Meeting (2018)

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