Post-translational modifications of meningococcal pili. Identification of common substituents: glycans and alpha-glycerophosphate--a review.

Neisseria meningitidis elaborate filamentous adhesins, pili or fimbriae, which belong to the type-4 structural group of pili also found on other bacterial pathogens such as Neisseria gonorrhoeae, Pseudomonas aeruginosa, Moraxella bovis and Dichelobacter nodosus. Meningococcal pili readily undergo structural variations which arise as a result of inter- and intra-genomic recombinational events. Structural variations often result in variations in bacterial adhesion mediated by pili. Studies on structure/function relationship of meningococcal pili have shown that pili are post-translationally modified and contain unusual covalently-linked substituents. The presence of glycans was shown by the use of specific carbohydrate labelling, chemical deglycosylation and by introducing galE mutations; the latter studies confirmed the presence of galactose on pili. Mass spectrometric and other analysis of pilin-derived tryptic peptides and linked substituents were used to determine the structure of an unusual O-linked trisaccharide, Gal beta1-4 Gal alpha1-3[2,4-diacetamido-2,4,6-trideoxyhexose]. Similar studies have also identified, perhaps a unique substituent, alpha-glycerophosphate, which is attached to Ser93 by a phosphodiester linkage.