Unique modifications with phosphocholine and phosphoethanolamine define alternate antigenic forms of Neisseria gonorrhoeae type IV pili.
Several major bacterial pathogens and related commensal species colonizing the human mucosa express phosphocholine (PC) at their cell surfaces. PC appears to impact host-microbe biology by serving as a ligand for both C-reactive protein and the receptor for platelet-activating factor. Type IV pili of Neisseria gonorrhoeae (Ng) and Neisseria meningitidis, filamentous protein structures critical to the colonization of their human hosts, are known to react variably with monoclonal antibodies recognizing a PC epitope. However, the structural basis for this reactivity has remained elusive. To address this matter, we exploited the finding that the PilE pilin subunit in Ng mutants lacking the PilV protein acquired the PC epitope independent of changes in pilin primary structure. Specifically, we show by using mass spectrometry that PilE derived from the pilV background is composed of a mixture of subunits bearing O-linked forms of either phosphoethanolamine (PE) or PC at the same residue, whereas the wild-type background carries only PE at that same site. Therefore, PilV can influence pilin structure and antigenicity by modulating the incorporation of these alternative modifications. The disaccharide covalently linked to Ng pilin was also characterized because it is present on the same peptides bearing the PE and PC modifications and, contrary to previous reports, was found to be linked by means of 2,4-diacetamido-2,4,6-trideoxyhexose. Taken together, these findings provide new insights into Ng type IV pilus structure and antigenicity and resolve long-standing issues regarding the nature of both the PC epitope and the pilin glycan.
Hegge
Finn Terje
FT
Centre for Molecular Biology and Neuroscience, University of Oslo, 0316 Oslo, Norway.
Hitchen
Paul G
PG
Aas
Finn Erik
FE
Kristiansen
Heidi
H
Løvold
Cecilia
C
Egge-Jacobsen
Wolfgang
W
Panico
Maria
M
Leong
Weng Yee
WY
Bull
Victoria
V
Virji
Mumtaz
M
Morris
Howard R
HR
Dell
Anne
A
Koomey
Michael
M
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D000939:Epitopes; D004983:Ethanolamines / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000737:chemistry* / Q000276:immunology; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009344:Neisseria gonorrhoeae / Q000276:immunology / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010767:Phosphorylcholine / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism
D000942:Antigens, Bacterial; D000939:Epitopes; D004983:Ethanolamines; D010455:Peptides; D021122:Protein Subunits; D010767:Phosphorylcholine; D036781:Fimbriae Proteins; C005448:phosphorylethanolamine