Role of iron and superoxide for generation of hydroxyl radical, oxidative DNA lesions, and mutagenesis in Escherichia coli.
We measured the generation of hydroxyl radical (OH(.)) and oxidative DNA lesions in aerobically grown Escherichia coli cells lacking in both superoxide dismutases (SodA SodB) and repressor of iron uptake (Fur) using electroparamagnetic resonance and gas chromatography-mass spectrometry with a selected-ion monitoring method. A specific signal corresponding to OH(.) generation and an increase in oxidative DNA lesions such as 7,8-dihydro-8-oxoguanine and 1,2-dihydro-2-oxoadenine were detected in the strain deficient in sodA sodB fur. We showed that iron metabolism deregulation in fur mutant produced a 2.5-fold iron overload. The sodA sodB fur strain was about 100-fold higher mutability than the wild-type strain. The mutation spectrum in the strain was found to induce GC --> TA and AT --> CG transversions predominantly. The hypermutability of the strain was suppressed by the tonB mutation which reduces iron transport. Thus, excess iron and excess superoxide were responsible for OH(.) generation, oxidative DNA lesion formation, and hypermutability in E. coli.
Nunoshiba
T
T
Biological Institute, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
Obata
F
F
Boss
A C
AC
Oikawa
S
S
Mori
T
T
Kawanishi
S
S
Yamamoto
K
K
D001426:Bacterial Proteins / Q000235:genetics; D003087:Colicins / Q000378:metabolism; D004249:DNA Damage; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D016153:Genes, Suppressor; D017665:Hydroxyl Radical / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics; D016296:Mutagenesis; D017354:Point Mutation; D012343:RNA, Transfer / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D012293:Rifampin / Q000378:metabolism; D019097:Spin Trapping; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
D001426:Bacterial Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; C096275:supF tRNA; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli; D013481:Superoxides; D017665:Hydroxyl Radical; D008345:Manganese; D012343:RNA, Transfer; D007501:Iron; C095500:SodA protein, Bacteria; C087504:SodB protein, Bacteria; D013482:Superoxide Dismutase; D012293:Rifampin