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Induction of an AP endonuclease activity in Streptococcus mutans during growth at low pH
Author(s) -
Hahn K.,
Faustoferri R. C.,
Quivey R. G.
Publication year - 1999
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1999.01292.x
Subject(s) - biology , streptococcus mutans , endonuclease , exonuclease , mutant , biochemistry , wild type , enzyme , microbiology and biotechnology , dna , polymerase , bacteria , genetics , gene
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 α‐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 ≈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.