title: Multiple species of Bacillus subtilis DNA alkyltransferase involved in the adaptive response to simple alkylating agents.
abstract: Three molecular species of methyl-accepting proteins exist in Bacillus subtilis cells, which collect methyl groups from methylated DNA. A 20-kilodalton (kDa) protein was constitutively present in the cells of the ada+ (proficient in adaptive response) strain as well as in those of six ada (deficient in adaptive response) mutant strains and was assigned to the O6-methylguanine:DNA methyltransferase. Another species of O6-methylguanine:DNA methyltransferase, which had a molecular size of 22 kDa, emerged after adaptive treatment of the ada+ but not any of the ada mutant cells. A 27-kDa methyl-accepting protein, which preferred methylated poly(dT) to methylated calf thymus DNA as a substrate, was assigned to the methylphosphotriester:DNA methyltransferase. It was produced, after adaptive treatment, in the cells of ada+, ada-3, ada-4, and ada-6 strains but not in the cells of ada-1, ada-2, or ada-5 strains. These results support and extend our proposition that ada mutants can be classified into two groups; one (the ada-4 group) is defective only in the inducible synthesis of O6-methylguanine:DNA methyltransferase (22-kDa protein), and the other (the ada-1 group) is deficient in the adaptive response in toto. The finding that inducible and constitutive methyltransferases reside in different molecular species of methyl-accepting proteins is intriguing compared with the regulatory mechanisms of the adaptive response to simple alkylating agents in other organisms.
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects / Q000201:enzymology*; D004790:Enzyme Induction; D007700:Kinetics; D008769:Methylnitronitrosoguanidine / Q000378:metabolism / Q000494:pharmacology*; D008770:Methylnitrosourea / Q000378:metabolism / Q000494:pharmacology; D008780:Methyltransferases / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D019853:O(6)-Methylguanine-DNA Methyltransferase; D013379:Substrate Specificity
chemical_list: D008769:Methylnitronitrosoguanidine; D008770:Methylnitrosourea; D008780:Methyltransferases; C045666:methylphosphotriester methyltransferase; D019853:O(6)-Methylguanine-DNA Methyltransferase