20220407 Lowary TL Epub

The biosynthetic origin of ribofuranose in bacterial polysaccharides

The biosynthetic origin of ribofuranose in bacterial polysaccharides

Nat Chem Biol. 2022 May; 18(5):530-537. Epub 2022 Apr 7.
doi: 10.1038/s41589-022-01006-6


Kelly SD, Williams DM, Nothof JT, Kim T, Lowary TL, Kimber MS*, Whitfield C*


Bacterial surface polysaccharides are assembled by glycosyltransferase enzymes that typically use sugar nucleotide or polyprenyl-monophosphosugar activated donors. Characterized representatives exist for many monosaccharides but neither the donor nor the corresponding glycosyltransferases have been definitively identified for ribofuranose residues found in some polysaccharides. Klebsiella pneumoniae O-antigen polysaccharides provided prototypes to identify dual-domain ribofuranosyltransferase proteins catalyzing a two-step reaction sequence. Phosphoribosyl-5-phospho-D-ribosyl-α-1-diphosphate serves as the donor for a glycan acceptor-specific phosphoribosyl transferase (gPRT), and a more promiscuous phosphoribosyl-phosphatase (PRP) then removes the residual 5'-phosphate. The 2.5-Å resolution crystal structure of a dual-domain ribofuranosyltransferase ortholog from Thermobacillus composti revealed a PRP domain that conserves many features of the phosphatase members of the haloacid dehalogenase family, and a gPRT domain that diverges substantially from all previously characterized phosphoribosyl transferases. The gPRT represents a new glycosyltransferase fold conserved in the most abundant ribofuranosyltransferase family.