title: AP endonuclease paralogues with distinct activities in DNA repair and bacterial pathogenesis.
abstract: Oxidative stress is a principal cause of DNA damage, and mechanisms to repair this damage are among the most highly conserved of biological processes. Oxidative stress is also used by phagocytes to attack bacterial pathogens in defence of the host. We have identified and characterised two apurinic/apyrimidinic (AP) endonuclease paralogues in the human pathogen Neisseria meningitidis. The presence of multiple versions of DNA repair enzymes in a single organism is usually thought to reflect redundancy in activities that are essential for cellular viability. We demonstrate here that these two AP endonuclease paralogues have distinct activities in DNA repair: one is a typical Neisserial AP endonuclease (NApe), whereas the other is a specialised 3'-phosphodiesterase Neisserial exonuclease (NExo). The lack of AP endonuclease activity of NExo is shown to be attributable to the presence of a histidine side chain, blocking the abasic ribose-binding site. Both enzymes are necessary for survival of N. meningitidis under oxidative stress and during bloodstream infection. The novel functional pairing of NExo and NApe is widespread among bacteria and appears to have evolved independently on several occasions.
authors.affiliation: Centre for Structural Biology, Division of Molecular Biosciences, Faculty of Natural Sciences, Imperial College London, London, UK.
authors.forename: Elisabeth P
authors.initials: EP
authors.lastname: Carpenter
authors.forename: Anne
authors.initials: A
authors.lastname: Corbett
authors.forename: Hellen
authors.initials: H
authors.lastname: Thomson
authors.forename: Jolanta
authors.initials: J
authors.lastname: Adacha
authors.forename: Kirsten
authors.initials: K
authors.lastname: Jensen
authors.forename: Julien
authors.initials: J
authors.lastname: Bergeron
authors.forename: Ioannis
authors.initials: I
authors.lastname: Kasampalidis
authors.forename: Rachel
authors.initials: R
authors.lastname: Exley
authors.forename: Megan
authors.initials: M
authors.lastname: Winterbotham
authors.forename: Christoph
authors.initials: C
authors.lastname: Tang
authors.forename: Geoff S
authors.initials: GS
authors.lastname: Baldwin
authors.forename: Paul
authors.initials: P
authors.lastname: Freemont
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D019295:Computational Biology; D018360:Crystallography, X-Ray; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006639:Histidine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009345:Neisseria meningitidis / Q000145:classification / Q000235:genetics / Q000472:pathogenicity; D018384:Oxidative Stress; D010802:Phylogeny; D017433:Protein Structure, Secondary; D051381:Rats; D017208:Rats, Wistar; D016415:Sequence Alignment; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006639:Histidine; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase