Abstract
BackgroundNeisseria meningitidis, the causative agent of meningococcal disease, is exposed to high levels of reactive oxygen species inside its exclusive human host. The DNA glycosylase Fpg of the base excision repair pathway (BER) is a central player in the correction of oxidative DNA damage. This study aimed at characterizing the meningococcal Fpg and its role in DNA repair.ResultsThe deduced N. meningitidis Fpg amino acid sequence was highly homologous to other Fpg orthologues, with particularly high conservation of functional domains. As for most N. meningitidis DNA repair genes, the fpg gene contained a DNA uptake sequence mediating efficient transformation of DNA. The recombinant N. meningitidis Fpg protein was over-expressed, purified to homogeneity and assessed for enzymatic activity. N. meningitidis Fpg was found to remove 2,6-diamino-4-hydroxy-5-formamidopyrimidine (faPy) lesions and 7,8-dihydro-8-oxo-2'-deoxyguanosine (8oxoG) opposite of C, T and G and to a lesser extent opposite of A. Moreover, the N. meningitidis fpg single mutant was only slightly affected in terms of an increase in the frequency of phase variation as compared to a mismatch repair mutant.ConclusionCollectively, these findings show that meningococcal Fpg functions are similar to those of prototype Fpg orthologues in other bacterial species.
Highlights
Neisseria meningitidis, the causative agent of meningococcal disease, is exposed to high levels of reactive oxygen species inside its exclusive human host
The Mc formamidopyrimidine-DNA glycosylase (Fpg) predicted structure and the activity pattern detected were similar to those of prototype Fpg orthologues in other species
We examined the activity and specificity of recombinant Mc Fpg purified to homogeneity towards representative substrates resulting from oxidative DNA damage, 8oxoG and faPy, and detected prototype Fpg glycosylase activity
Summary
The causative agent of meningococcal disease, is exposed to high levels of reactive oxygen species inside its exclusive human host. The DNA glycosylase Fpg of the base excision repair pathway (BER) is a central player in the correction of oxidative DNA damage. The meningococcus (Mc), exclusively colonizes the oro- and nasopharynx of humans. It resides as a commensal in approximately 10% of healthy individuals [1], but may become virulent, disseminating into the bloodstream and crossing the blood-brain barrier [2]. Oxidative DNA lesions comprise single- and double strand breaks, abasic (apurinic/apyrimidinic, or AP) sites, and base damages, among which one of the most common is the oxidation product of guanine, 7,8-dihydro-8-oxo-2'deoxyguanosine (8oxoG). The mutagenic 8oxoG can mispair with adenine during replication and cause G:C → T:A transversions [4]. 2,6-diamino-4-hydroxy-5-formamidopyrimidine (faPy) is another oxidative modified form of guanine that inhibits DNA synthesis [5]
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