RESUMO
AniA of the pathogenic Neisseria is glycosylated in its C-terminal repeat region by the pilin glycosylation (pgl) pathway. AniA appears to be unique among bacterial nitrite reductases as it contains an N-terminal extension that includes a lipid modification site as well as a C-terminal extension that is glycosylated. Immunising with various glycoforms of the AniA protein demonstrated a strong humoral immune response to the basal monosaccharide. In addition, when animals were immunised with a truncated form of AniA, completely lacking the glycosylated C-terminal region, the antibody response was directed against AniA regardless of the glycosylation state of the protein. Immuno-SEM confirmed that AniA is expressed on the cell surface in Neisseria gonorrhoeae. Antisera generated against a truncated, non-glycosylated, recombinant form of the AniA protein are capable of blocking nitrite reductase function in a whole cell assay. We propose that recombinant modified AniA has potential as a vaccine antigen for N. gonorrhoeae.
Assuntos
Anticorpos Bloqueadores/biossíntese , Antígenos de Bactérias/imunologia , Proteínas da Membrana Bacteriana Externa/imunologia , Neisseria gonorrhoeae/imunologia , Nitrito Redutases/imunologia , Anticorpos Bloqueadores/imunologia , Antígenos de Bactérias/genética , Antígenos de Bactérias/metabolismo , Proteínas da Membrana Bacteriana Externa/genética , Proteínas da Membrana Bacteriana Externa/metabolismo , Vacinas Bacterianas/genética , Vacinas Bacterianas/imunologia , Glicosilação , Neisseria gonorrhoeae/enzimologia , Nitrito Redutases/genética , Nitrito Redutases/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Proteínas Recombinantes/metabolismoRESUMO
O-glycosylation of proteins in Neisseria meningitidis is catalyzed by PglL, which belongs to a protein family including WaaL O-antigen ligases. We developed two hidden Markov models that identify 31 novel candidate PglL homologs in diverse bacterial species, and describe several conserved sequence and structural features. Most of these genes are adjacent to possible novel target proteins for glycosylation. We show that in the general glycosylation system of N. meningitidis, efficient glycosylation of additional protein substrates requires local structural similarity to the pilin acceptor site. For some Neisserial PglL substrates identified by sensitive analytical approaches, only a small fraction of the total protein pool is modified in the native organism, whereas others are completely glycosylated. Our results show that bacterial protein O-glycosylation is common, and that substrate selection in the general Neisserial system is dominated by recognition of structural homology.