title: The glucosyl-1-phosphate transferase WchA (Cap8E) primes the capsular polysaccharide repeat unit biosynthesis of Streptococcus pneumoniae serotype 8.
abstract: The gene wchA (cap8E) belongs to the cps8 locus that is involved in biosynthesis of the capsular polysaccharide (CPS) repeat unit (RU) of the virulent Streptococcus pneumoniae serotype 8. We report here the biochemical characterization of the membrane-associated protein WchA (Cap8E), overexpressed in Escherichia coli BL21(DE3)/pLysS. Our results demonstrate that the recombinant enzyme transfers in vitro a glucosyl-1-phosphate from UDP-glucose to an endogenous phosphoryl-polyprenol, thereby priming the RU biosynthetic pathway of S. pneumoniae CPS 8. We also show that the C-terminal half of WchA is the glycosyltransferase domain as observed for the galactosyl-1-phosphate transferase WbaP from Salmonella enterica, previously described to prime the first step of O-antigen biosynthesis. These results demonstrate that WchA plays a prominent function in the capsule biosynthesis and explain the key role it occupies in the pneumococcal capsule variation.
authors.affiliation: Laboratoire Adaptation et Pathogénie des Micro-organismes, CNRS UMR 5163, Institut Jean Roget, Faculté de Médecine Pharmacie, Domaine de La Merci, 38700 La Tronche, France. ludovic.pelosi@ujf-grenoble.fr
authors.forename: Ludovic
authors.initials: L
authors.lastname: Pelosi
authors.forename: Manel
authors.initials: M
authors.lastname: Boumedienne
authors.forename: Nehmé
authors.initials: N
authors.lastname: Saksouk
authors.forename: Johannes
authors.initials: J
authors.lastname: Geiselmann
authors.forename: Roberto A
authors.initials: RA
authors.lastname: Geremia
mesh_terms: D016667:Bacterial Capsules / Q000096:biosynthesis*; D001483:Base Sequence; D002855:Chromatography, Thin Layer; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D014644:Genetic Variation; D005960:Glucosides / Q000378:metabolism; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D007553:Isotope Labeling; D008969:Molecular Sequence Data; D019081:O Antigens / Q000096:biosynthesis; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000235:genetics; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000378:metabolism*
chemical_list: D005960:Glucosides; D019081:O Antigens; D011135:Polysaccharides, Bacterial; C121798:pneumococcal polysaccharide, type 8; D016695:Glycosyltransferases