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Genes Cells. 2003 Dec;8(12):941-50.

Suppression of spontaneous and hydrogen peroxide-induced mutations by a MutT-type nucleotide pool sanitization enzyme, the Escherichia coli Orf135 protein.

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Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.



We recently found that the Escherichia coli Orf135 protein, a MutT-type enzyme, hydrolysed 2-hydroxy-dATP (2-OH-dATP), and less efficiently, 8-hydroxy-dGTP.


In this study, we examined the effects of the absence of the orf135 gene. Frequencies of spontaneous and H2O2-induced mutations were two- to three-fold higher in the orf135- strain than in the wild-type strain. These mutations include various mutations involving a G:C-->T:A transversion, the same type of mutation elicited by 2-OH-dATP. Over-expression of the Orf135 protein suppressed mutations even in the wild-type strain, as well as in the orf135- strain.


The mutator phenotype of bacteria lacking the Orf135 protein suggests that this protein is involved in the suppression of mutations induced by oxidized deoxynucleotides in vivo and that various MutT-type enzymes contribute to nucleotide pool sanitization.

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