Meningococcal pilin: a glycoprotein substituted with digalactosyl 2,4-diacetamido-2,4,6-trideoxyhexose.
Neisseria meningitidis pili are filamentous protein structures that are essential adhesins in capsulate bacteria. Pili of adhesion variants of meningococcal strain C311 contain glycosyl residues on pilin (PilE), their major structural subunit. Despite the presence of three potential N-linked glycosylation sites, none appears to be occupied in these pilins. Instead, a novel O-linked trisaccharide substituent, not previously found as a constituent of glycoproteins, is present within a peptide spanning amino acid residues 45 to 73 of the PilE molecule. This structure contains a terminal 1-4-linked digalactose moiety covalently linked to a 2,4-diacetamido-2,4,6-trideoxyhexose sugar which is directly attached to pilin. Pilins derived from galactose epimerase (galE) mutants lack the digalactosyl moiety, but retain the diacetamidotrideoxyhexose substitution. Both parental (#3) pilins and those derived from a hyper-adherent variant (#16) contained identical sugar substitutions in this region of pilin, and galE mutants of #3 were similar to the parental phenotype in their adherence to host cells. These studies have confirmed our previous observations that meningococcal pili are glycosylated and provided the first structural evidence for the presence of covalently linked carbohydrate on pili. In addition, they have revealed a completely novel protein/saccharide linkage.
Stimson
E
E
Department of Paediatrics, University of Oxford, John Radcliffe Hospital, UK.
Virji
M
M
Makepeace
K
K
Dell
A
A
Morris
H R
HR
Payne
G
G
Saunders
J R
JR
Jennings
M P
MP
Barker
S
S
Panico
M
M
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D001483:Base Sequence; D002238:Carbohydrate Epimerases / Q000378:metabolism; D002240:Carbohydrate Sequence; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000737:chemistry*; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000737:chemistry*; D016415:Sequence Alignment; D014312:Trisaccharides / Q000032:analysis*; D014534:UDPglucose 4-Epimerase
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; D014312:Trisaccharides; C074063:pilE protein, Neisseria gonorrhoeae; D036781:Fimbriae Proteins; D002238:Carbohydrate Epimerases; D014534:UDPglucose 4-Epimerase; C020551:galactose epimerase