title: Induction of an AP endonuclease activity in Streptococcus mutans during growth at low pH.
abstract: The oral microbe Streptococcus mutans uses adaptive mechanisms to withstand the fluctuating pH levels in its natural environment. The regulation of protein synthesis is part of the mechanism of acid adaptation and tolerance in S. mutans. Here, we demonstrate that the organism's acid-inducible protein repertoire includes an AP endonuclease activity. This abasic site-specific endonuclease activity is present at greater levels in cells grown at low pH than in cells grown at pH 7, and is apparently independent of the RecA protein. Experiments using tetrahydrofuran or alpha-deoxyadenosine-containing substrates indicate that the activity induced at low pH may be similar to the activity of exonuclease III from E. coli. Acid-adapted S. mutans also shows an increased survival rate after exposure to near-UV radiation in both the wild type and a recA strain. Far-UV radiation resistance is observed in the wild type only. The endonuclease activity was purified approximately 500-fold from an S. mutans recA mutant strain grown at pH 5. Initial characterization revealed a 3' to 5' exonuclease activity, and showed additional functional similarities to DNA repair enzymes from other organisms.
authors: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, NY 14642, USA.
authors: K
authors: K
authors: Hahn
authors: R C
authors: RC
authors: Faustoferri
authors: R G
authors: RG
authors: Quivey
mesh_terms: D002122:Calcium Chloride / Q000494:pharmacology; D019757:Carbon-Oxygen Lyases / Q000302:isolation & purification / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000494:pharmacology; D004790:Enzyme Induction; D005947:Glucose / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D015636:Magnesium Chloride / Q000494:pharmacology; D011938:Rec A Recombinases / Q000378:metabolism; D013295:Streptococcus mutans / Q000201:enzymology* / Q000254:growth & development*; D013997:Time Factors; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D002614:Chelating Agents; D015636:Magnesium Chloride; D004247:DNA; D004492:Edetic Acid; D011938:Rec A Recombinases; D043223:Deoxyribonuclease IV (Phage T4-Induced); D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D005947:Glucose; D002122:Calcium Chloride