Sweet Talk: Protein Glycosylation in Bacterial Interaction With the Host

Pathogenic bacteria encode virulent glycosyltransferases that conjugate various glycans onto substrate proteins via the N- or O-linkage. The HMW system in nontypeable Haemophilus influenzae and the Pgl system in Campylobacter jejuni glycosylate bacterial surface or periplasmic proteins at the eukaryotic-like Asn-X-Ser/Thr motif. The NleB effector from enterobacteria mediates arginine GlcNAcylation of host death-domain proteins to block inflammation, representing an atypical N-glycosylation. The large clostridial cytotoxins and related glucosyltransferase toxins from Legionella and Photorhabdus monoglycosylate a serine/threonine or tyrosine in host Rho GTPase or elongation factor 1A (eEF1A). The emerging bacterial autotransporter heptosyltransferase (BAHT) family of heptosyltransferases also catalyses O-glycosylation and modifies autotransporters for adhesion to the host. These glycosylations, diverse in linkages and glycan structures, determine appropriate functioning of bacterial virulence factors or hijack host cellular processes in pathogenesis.

TrendsBacteria have evolved chemically diverse glycosylation systems for pathogenesis.Bacterial glycosylation not only allows adhesion to the host cell but also functions to modulate crucial host cellular processes.An enteropathogenic Escherichia coli (EPEC) type III effector NleB catalyses arginine GlcNAcylation of host death-domain proteins to block cell death and suppress inflammation.The Photorhabdus asymbiotica protein toxin (PaTox) modifies Rho GTPase by GlcNAcylation of a tyrosine residue.A large bacterial autotransporter heptosyltransferase (BAHT) family mediates O-linked hyperheptosylation of bacterial autotransporters through an unprecedented structural mechanism.The serine-rich repeat protein (SRRP) Fap1 from an oral streptococcal bacterium is sequentially modified by multiple glycosyltransferases, of which dGT1 adopts a glycosyltransferase fold different from all known ones.