Multiple species of Bacillus subtilis DNA alkyltransferase involved in the adaptive response to simple alkylating agents
Multiple species of Bacillus subtilis DNA alkyltransferase involved in the adaptive response to simple alkylating agents
复制标题
多种枯草芽孢杆菌 DNA 烷基转移酶参与对简单烷化剂的适应性反应
作者：
F. Morohoshi;N. Munakata
枯草芽孢杆菌细胞中存在三种甲基接受蛋白，它们从甲基化的DNA中收集甲基。在ada+（精通适应性反应）菌株和6个ada（缺乏适应性反应）突变菌株的细胞中，存在一个20千顿（kDa）蛋白，该蛋白被分配到o6 -甲基鸟嘌呤：DNA甲基转移酶上。另一种o6 -甲基鸟嘌呤：DNA甲基转移酶，其分子大小为22 kDa，在ada+细胞的适应性处理后出现，但在ada突变细胞中没有出现。一个27 kda的甲基化接受蛋白，它更倾向于甲基化聚（dT）而不是甲基化小牛胸腺DNA作为底物，被分配到甲基化磷酸三酯：DNA甲基转移酶。在适应处理后，ada+、ada-3、ada-4和ada-6株细胞中产生了该蛋白，但在ada-1、ada-2和ada-5株细胞中不产生。这些结果支持并扩展了ada突变体可分为两类的命题；一个（ada-4组）仅在诱导合成o6 -甲基鸟嘌呤：DNA甲基转移酶（22-kDa蛋白）方面存在缺陷，另一个（ada-1组）在toto的适应性反应方面存在缺陷。与其他生物对简单烷基化剂的适应性反应的调节机制相比，诱导型和组成型甲基转移酶存在于不同的甲基接受蛋白分子物种中，这一发现令人感兴趣。
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.