Extended Data Fig. 10: Likely mechanism of alternating substrate polymerization and comparison with cellulose synthase.

(a) Superimposition of substrate-bound and primed Cv-HAS structures. The close distance between the primer and donor sugar is indicated by grey bars. (b) Contact likelihood between C231 and GlcNAc for the systems in a over the last 125 ns of each simulation. In the case of GlcNAc being in both donor and acceptor positions, both GlcNAc units are less likely to bind C231, and exhibit very high variance regarding binding poses. Of particular note, the chance of both GlcNAc being in the C231 pocket at the same time is very low (ca. 1.5 ± 0.8%). (c) Cv-HAS is superimposed with the Rhodobacter sphaeroides (Rs) BcsA-B complex (PDB: 4P00) based on secondary structure matching. Rs-BcsA-B is coloured grey and Cv-HAS is coloured blue and green for its TM and GT domains. The cellulose polymer associated with Rs-BcsA-B is shown as black sticks.