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Sequence analysis and relationships between meningococcal class 3 serotype proteins and other porins from pathogenic
M J Ward1, P R Lambden, J E Heckels
1Department of Microbiology, Southampton University Medical School, Southampton General Hospital, UK.
Abstract:
The presence of highly conserved regions within previously determined porin gene sequences from Neisseria meningitidis and Neisseria gonorrhoeae permitted the construction of oligonucleotide primers for PCR amplification of other neisserial porin genes. Although two separate porin genes (porA and porB) are present in N. meningitidis only a single fragment, corresponding to porB, could be amplified from this species. The amplified porB genes from four different meningococcal serotypes, which express the class 3 outer membrane protein, were sequenced. Amplified fragments corresponding to porin genes from N. lactamica and N. sicca were also sequenced. In common with the known neisserial porins, models of the organisation of the predicted proteins indicated trans-membrane structures with eight surface exposed loops. In the meningococcal class 3 proteins the main regions of sequence variation, which must be responsible for serotype specificity, were located on loops 5 and 7. A phylogenetic analysis of the family of porins from the Neisseria confirmed the close relationship of the meningococcal class 3 protein with the gonococcal PIA protein, while the gonococcal PIB protein was shown to be closely related to the N. lactamica porin. The close relationship seen between porins of the pathogenic and non-pathogenic Neisseriae identified no obvious virulence-associated regions in the proteins, but did suggest that the current nomenclature for neisserial porin genes may need reviewing.
Insights
Highly conserved regions in Neisseria porin genes allowed PCR amplification and sequencing. Analysis revealed conserved structures and identified key variation sites in meningococcal class 3 porins, suggesting nomenclature review.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Porins are outer membrane proteins crucial for Neisseria species.
- Conserved regions in Neisseria meningitidis and Neisseria gonorrhoeae porin genes facilitate primer design.
- Understanding porin diversity is key to Neisseria pathogenesis and classification.
Purpose of the Study:
- To amplify and sequence porin genes from various Neisseria species using PCR.
- To analyze the sequence variation and structural organization of Neisseria porins.
- To investigate the phylogenetic relationships among Neisseria porins and their implications for classification.
Main Methods:
- Polymerase Chain Reaction (PCR) amplification using conserved oligonucleotide primers.
- DNA sequencing of amplified porin gene fragments (porB).
- Bioinformatic analysis including protein structure modeling and phylogenetic analysis.
Main Results:
- Successfully amplified and sequenced porB genes from N. meningitidis serotypes expressing class 3 outer membrane protein.
- Sequenced porin genes from N. lactamica and N. sicca.
- Identified conserved trans-membrane structures with eight surface-exposed loops; sequence variations in loops 5 and 7 correlated with serotype specificity in meningococcal class 3 porins.
- Phylogenetic analysis revealed close relationships between meningococcal class 3 porins and gonococcal PIA, and between gonococcal PIB and N. lactamica porins.
Conclusions:
- The study successfully characterized porin genes across different Neisseria species.
- Sequence variations in specific loops (5 and 7) are critical for serotype specificity in N. meningitidis class 3 porins.
- The close evolutionary relationship between pathogenic and non-pathogenic Neisseria porins suggests that current gene nomenclature may require revision.