biostudies-literatureGriffiths RBiotechnology and Biological Sciences Research Council708-717https://www.ebi.ac.uk/biostudies/studies/S-EPMC12809243biostudies-literatureUnknown81(Pt 12)The accessory secretion (aSec) system is a protein export pathway that is uniquely present in Gram-positive bacteria and is dedicated to the secretion of large, glycosylated cell wall-anchored adhesins called serine-rich repeat proteins (SRRPs). Strain-specific glycosylation of SRRPs has previously been reported in Limosilactobacillus reuteri and attributed to GtfC, a glycosyltransferase belonging to family 113, with LrGtfC_100-23 from L. reuteri rat strain 100-23C showing specificity for UDP-Glc, while LrGtfC₅₃₆₀₈ from L. reuteri pig strain ATCC 53608, which differs at only ten amino-acid positions, shows a preference for UDP-GlcNAc. However, the structural basis underpinning GtfC sugar-donor specificity remains unclear. Here, we report X-ray crystal structures of theActa crystallographica. Section D, Structural biologyA structural basis for the strain-dependent UDP-sugar specificity of glycosyltransferase C from the Limosilactobacillus reuteri accessory secretion system.PMC12809243BB/R012490/1BB/X011054/1BB/M011216/1Juge NGriffiths RAshworth GHemmings APfalzgraf HDong CLatousakis DfalseA structural basis for the strain-dependent UDP-sugar specificity of glycosyltransferase C from the Limosilactobacillus reuteri accessory secretion system.The accessory secretion (aSec) system is a protein export pathway that is uniquely present in Gram-positive bacteria and is dedicated to the secretion of large, glycosylated cell wall-anchored adhesins called serine-rich repeat proteins (SRRPs). Strain-specific glycosylation of SRRPs has previously been reported in Limosilactobacillus reuteri and attributed to GtfC, a glycosyltransferase belonging to family 113, with LrGtfC_100-23 from L. reuteri rat strain 100-23C showing specificity for UDP-Glc, while LrGtfC₅₃₆₀₈ from L. reuteri pig strain ATCC 53608, which differs at only ten amino-acid positions, shows a preference for UDP-GlcNAc. However, the structural basis underpinning GtfC sugar-donor specificity remains unclear. Here, we report X-ray crystal structures of the2025-01-01T00:00:00Z2025 Dec2026-06-06T16:02:40.725Z2026-06-02T03:09:49.864ZS-EPMC128092434119065810.1107/S2059798325008782