| Summary: | <p>Abstract</p> <p>Background</p> <p>It has been speculated that the γ-glutamyl transpeptidase (<it>ggt</it>) gene is present only in <it>Neisseria meningitidis </it>and not among related species such as <it>Neisseria gonorrhoeae </it>and <it>Neisseria lactamica</it>, because <it>N. meningitidis </it>is the only bacterium with GGT activity. However, nucleotide sequences highly homologous to the meningococcal <it>ggt </it>gene were found in the genomes of <it>N. gonorrhoeae </it>isolates.</p> <p>Results</p> <p>The gonococcal homologue (<it>ggt </it>gonococcal homologue; <it>ggh</it>) was analyzed. The nucleotide sequence of the <it>ggh </it>gene was approximately 95 % identical to that of the meningococcal <it>ggt </it>gene. An open reading frame in the <it>ggh </it>gene was disrupted by an ochre mutation and frameshift mutations induced by a 7-base deletion, but the amino acid sequences deduced from the artificially corrected <it>ggh </it>nucleotide sequences were approximately 97 % identical to that of the meningococcal <it>ggt </it>gene. The analyses of the sequences flanking the <it>ggt </it>and <it>ggh </it>genes revealed that both genes were localized in a common DNA region containing the <it>fbp-ggt </it>(or <it>ggh)-glyA-opcA-dedA-abcZ </it>gene cluster. The expression of the <it>ggh </it>RNA could be detected by dot blot, RT-PCR and primer extension analyses. Moreover, the truncated form of <it>ggh-</it>translational product was also found in some of the gonococcal isolates.</p> <p>Conclusion</p> <p>This study has shown that the gonococcal <it>ggh </it>gene is a pseudogene of the meningococcal <it>ggt </it>gene, which can also be designated as Ψ<it>ggt</it>. The gonococcal <it>ggh </it>(Ψ<it>ggt</it>) gene is the first identified bacterial pseudogene that is transcriptionally active but phenotypically silent.</p>
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