Naturally occurring PIA/PIB hybrids of Neisseria gonorrhoeae

Gill, Martin J.

doi:10.1016/0378-1097(94)90408-1

Cited by 7 publications

(13 citation statements)

References 13 publications

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“…Individual strains express only one of the two PorB protein groups, either PorB1a or PorB1b (4,6,11,29), which are encoded by the mutually exclusive porB gene alleles, porB1a and porB1b, respectively. Naturally but rarely occurring strains that express PorB1a-PorB1b hybrids have been identified (4,9). Antigenic diversities of PorB between strains form the basis for the widely used serogroup and serovar determination with monoclonal antibodies (MAbs) (14,22), and attempts at identifying the antigenic epitopes of PorB of the serovar-specific MAbs have previously been published (1,3,4,5,16,27).…”

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Molecular Typing of Neisseria gonorrhoeae Isolates by Pyrosequencing of Highly Polymorphic Segments of the porB Gene

et al. 2004

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For prevention and control of gonorrhea, an objective, highly discriminating, and reproducible molecular epidemiological characterization of Neisseria gonorrhoeae is essential. In the present study, in pursuance of providing such qualities, pyrosequencing technology, a fast real-time DNA sequence analysis, was applied to six short, highly polymorphic porB gene segments, with subsequent genetic variant (genovar) determination of the bacterial isolates. The sequencing templates were obtained by real-time PCR amplification, which also included fluorescence melting curve analysis of the entire porB gene in order to determine the genogroup (porB1a or porB1b allele) prior to pyrosequencing analysis. The PSQ 96 MA system used allowed rapid (in approximately 1.5 h) determination of 96 sequences of 20 to 65 correct nucleotides each. The results were reproducible and mostly in concordance with the results of conventional Sanger dideoxy sequencing, with the exception of shorter read lengths and some uncertainty in determining the correct number of identical nucleotides in homopolymeric segments. The number of sequence variants identified in each of the six highly polymorphic segments of the porB1a and porB1b alleles (encoding surface-exposed amino acid loops of the mature PorB protein) ranged from 5 to 11 and from 8 to 39, respectively. Among porB1a isolates (n ‫؍‬ 22) and porB1b isolates (n ‫؍‬ 65), 22 and 64 unique genovars, respectively, were identified. All isolates were typeable. The present results provide evidence of a high discriminatory ability, practically the same as that for sequencing of the entire porB gene. In conclusion, the fast and high-throughput pyrosequencing technology can be used for molecular epidemiological characterization of N. gonorrhoeae.

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Molecular Typing of Neisseria gonorrhoeae Isolates by Pyrosequencing of Highly Polymorphic Segments of the porB Gene

et al. 2004

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“…Any individual strain expresses only one of the groups, either PorB1a or PorB1b (3,5,11,32). However, naturally occurring strains that express PorB1a/PorB1b hybrids have been identified (3,9). The proteins PorB1a and PorB1b are encoded by the mutually exclusive alleles of the porB gene, porB1a and porB1b, respectively (5,11).…”

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Comparison of Serologic and Genetic porB -Based Typing of Neisseria gonorrhoeae : Consequences for Future Characterization

et al. 2003

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Due to temporal changes in the epidemiology of gonorrhea, a precise characterization of Neisseria gonorrhoeae is essential. In the present study genetic heterogeneity in the porB genes of N. gonorrhoeae was examined, and serovar determination was compared to porB gene sequencing. Among 108 N. gonorrhoeae isolates, phylogenetic analysis of the entire porB alleles (924 to 993 bp) identified 87 unique sequences. By analyzing only the four to six most heterogeneous porB gene regions (174 to 363 bp), 86 out of these 87 genetic variants were identified. Consequently, analysis of shorter highly variable regions of the porB gene generates high-level discriminatory ability as well as fast, objective, reproducible, and portable data for epidemiological characterization of N. gonorrhoeae. Regarding putative antigenic epitopes of PorB for Genetic Systems monoclonal antibodies (MAbs), some of the previous findings were confirmed, but new findings were also observed. For several of the MAbs, however, the precise amino acid residues of PorB critical for single-MAb reactivity were difficult to identify. In addition, repeated serovar determination of 108 N. gonorrhoeae isolates revealed discrepancies for 34 isolates, mostly due to nonreproducible reactivity with single MAbs. Thus, the prospects of a genetic typing system with congruent translation of the serovar determination seem to be limited. In conclusion, analysis of short highly variable regions of the porB gene could form the basis for a fast molecular epidemiological tool for the examination of emergence and transmission of N. gonorrhoeae strains within the community.

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“…Sequence changes have been reported for loop domains in different Por1A serovars (32), and recent work indicates that Por1B polypeptides within the same serovar can differ in primary sequences of loops V and VI (others were not assessed) (37). In addition, Por1A-1B mosaics have been identified among clinical isolates (19). Por1A-1B mosaics, in addition to those that we examined, can be constructed by reassortment of Por1A and Por1B loop domains.…”

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Porin polypeptide contributes to surface charge of gonococci

et al. 1997

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Each strain of Neisseria gonorrhoeae elaborates a single porin polypeptide, with the porins expressed by different strains comprising two general classes, Por1A and Por1B. In the outer membrane, each porin molecule folds into 16 membrane-spanning ␤-strands joined by top-and bottom-loop domains. Por1A and Por1B have similar membrane-spanning regions, but the eight surface-exposed top loops (I to VIII) differ in length and sequence. To determine whether porins, and especially their top loop domains, contribute to bacterial cell surface charge, strain MS11 gonococci that were identical except for expressing a recombinant Por1A, Por1B, or mosaic Por1A-1B polypeptide were compared by whole-cell electrophoresis. These porin variants displayed different electrophoretic mobilities that correlated with the net numbers of charged amino acids within surface-exposed loops of their respective porin polypeptides. The susceptibilities of porin variants to polyanionic sulfated polymers correlated roughly with gonococcal surface charge; those porin variants with diminished surface negativity showed increased sensitivity to the polyanionic sulfated compounds. These observations indicate that porin polypeptides in situ contribute to the surface charge of gonococci, and they suggest that the bacterium's interactions with large sulfated compounds are thereby affected.Porin polypeptide is quantitatively prominent in the gonococcal outer membrane (22,27), where it trimerizes and forms water-filled, voltage-regulated, anion-favoring pores that transport charged, hydrophilic atoms and small molecules across the outer membrane (14, 53). Each gonococcal genome contains a single porin gene whose protein product is identical in all variants of a given strain and formerly has been designated major outer membrane protein, principal outer membrane protein, and protein I. Gonococci (Gc) from diverse strains express porin molecules that generally fall into one of two general classes, Por1A and Por1B (5,10,20); these were initially differentiated by their molecular weight, protease susceptibility, and reactivity with monoclonal antibodies (3,16,30). The primary sequences of Por1A and Por1B porin polypeptides are nearly identical in their membrane-spanning regions but are quite different in surface-exposed domains, as predicted (47) and largely confirmed by antibody epitope mapping (5,18,32,49).Several biological attributes of Gc have been correlated with which porin they produce. Por1A organisms predominate among isolates from systemic infections (4, 7), are usually more resistant than Por1B bacteria to killing by normal human sera (24), and are less resistant than Por1B cells to several antibiotics (6); these differences have been confirmed with Gc that express recombinant porin polypeptides (8). The molecular bases for the apparent relationships between porin phenotype and biological behaviors are unknown.Gram-negative bacteria generally exhibit a net negative surface charge (25), whose molecular origins are incompletely defined except for caps...

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Naturally occurring PIA/PIB hybrids of Neisseria gonorrhoeae

Cited by 7 publications

References 13 publications

Molecular Typing of Neisseria gonorrhoeae Isolates by Pyrosequencing of Highly Polymorphic Segments of the porB Gene

Molecular Typing of Neisseria gonorrhoeae Isolates by Pyrosequencing of Highly Polymorphic Segments of the porB Gene

Comparison of Serologic and Genetic porB -Based Typing of Neisseria gonorrhoeae : Consequences for Future Characterization

Porin polypeptide contributes to surface charge of gonococci

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