Open AccessO6-methylguanine-DNA methyltransferase in wild-type and ada mutants of Escherichia coli
Author(s) -
Sankar Mitra,
Bimal C. Pal,
Robert S. Foote
Publication year - 1982
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.152.1.534-537.1982
Subject(s) - biology , escherichia coli , methyltransferase , mutant , microbiology and biotechnology , dna , mutation , dna methyltransferase , enzyme , biochemistry , gene , methylation
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.