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Escherichia coli Dps interacts with DnaA protein to impede initiation: a model of adaptive mutation
Author(s) -
Chodavarapu Sundari,
Gomez Ruben,
Vicente Matias,
Kaguni Jon M.
Publication year - 2008
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 - 10.1111/j.1365-2958.2008.06127.x
Subject(s) - dnaa , biology , sos response , plasmid , oxidative stress , mutation , genetics , dna damage , dna , dna replication , microbiology and biotechnology , mutagenesis , escherichia coli , gene , biochemistry , origin of replication
Summary During exponential growth, the level of Dps transiently increases in response to oxidative stress to sequester and oxidize Fe 2+ , which would otherwise lead to hydroxyl radicals that damage the bacterial chromosome. We report that Dps specifically interacts with DnaA protein by affinity chromatography and a solid phase binding assay, requiring the N‐terminal region of DnaA to interact. In vitro , Dps inhibits DnaA function in initiation by interfering with strand opening of the replication origin. Comparing isogenic dps + and dps :: kan strains by flow cytometry and by quantitative polymerase chain reaction assays at either the chromosomally encoded level, or at an elevated level encoded by an inducible plasmid, we show that Dps causes less frequent initiations. Results from genetic experiments support this conclusion. We suggest that Dps acts as a checkpoint during oxidative stress to reduce initiations, providing an opportunity for mechanisms to repair oxidative DNA damage. Because Dps does not block initiations absolutely, duplication of the damaged DNA is expected to increase the genetic variation of a population, and the probability that genetic adaptation leads to survival under conditions of oxidative stress.