title: O6-methylguanine-DNA methyltransferase in wild-type and ada mutants of Escherichia coli.
abstract: O(6)-Methylguanine-DNA methyltransferase is induced in Escherichia coli during growth in low levels of N-methyl-N'-nitro-N-nitrosoguanidine. We have developed a sensitive assay for quantitating low levels of this activity with a synthetic DNA substrate containing 3H-labeled O(6)-methylguanine as the only modified base. Although both wild-type and adaptation-deficient (ada) mutants of E. coli contained low but comparable numbers (from 13 to 60) of the enzyme molecules per cell, adaptation treatment caused a significant increase of the enzyme in the wild type but not in the ada mutants, suggesting that the ada mutation is in a regulatory locus and not in the structural gene for the methyltransferase.
mesh_terms: D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005798:Genes, Bacterial; D005809:Genes, Regulator; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D019853:O(6)-Methylguanine-DNA Methyltransferase
chemical_list: D006147:Guanine; C008449:O-(6)-methylguanine; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase