Identification of the Clostridial cellulose synthase and characterization of the cognate glycosyl hydrolase, CcsZ
Fig 2
The ccsZABHI gene cluster shares predicted structural and functional similarity, but not homology, to the Gram-negative O-acetylated cellulose synthase.
Proteins are coloured as in Fig 1. (A) The model of the P. fluorescens SBW25 cellulose synthase based on Spiers et al. [11] that contains putative O-acetyltransferases resembling those of the alginate biosynthesis pathway in P. aeruginosa. (B) Our proposed model of the cellulose synthase from selected Clostridia. The synthases we identified (CcsA) contain the hallmark GT-2 and PilZ domains of Gram-negative cellulose synthases, in addition to CcsB, a membrane-bound extracellular protein of unknown function. O-Acetylation of cellulose in this pathway is likely carried out by CcsH and CcsI, which resemble PatA1 and PatB1 from B. cereus, as well as WssH and WssI from P. fluorescens SBW25, and cleavage is carried out by the GH-5 enzyme CcsZ reported here.