Gubler M, Braguglia D, Meyer J, Piekarowicz A, Bickle T A
Department of Microbiology, Basel University, Switzerland.
EMBO J. 1992 Jan;11(1):233-40. doi: 10.1002/j.1460-2075.1992.tb05046.x.
EcoR124 and EcoDXXI are allelic type I restriction-modification (R-M) systems whose specificity genes consist of common structural elements: two variable regions are separated by a constant, homologous region containing a number of repetitive sequence elements. In vitro recombination of variable and constant elements has led to fully active, hybrid R-M systems exhibiting new and predictable target site specificities. Methylation of synthetic DNA sequences with purified, hybrid modification methylases was used to confirm the proposed recognition sequences. The results clearly demonstrate the correlation between protein domains and target site specificity. Our data suggest that a bacterial population may switch the recognition sequences of its type I R-M system by single recombination events and thus is able to maintain a prokaryotic analogue of the immune system of variable specificity.
EcoR124和EcoDXXI是等位基因I型限制-修饰（R-M）系统，其特异性基因由常见的结构元件组成：两个可变区被一个恒定的同源区隔开，该同源区包含许多重复序列元件。可变元件和恒定元件的体外重组产生了具有完全活性的杂交R-M系统，这些系统表现出新的、可预测的靶位点特异性。使用纯化的杂交修饰甲基化酶对合成DNA序列进行甲基化，以确认所提出的识别序列。结果清楚地证明了蛋白质结构域与靶位点特异性之间的相关性。我们的数据表明，细菌群体可能通过单次重组事件切换其I型R-M系统的识别序列，从而能够维持可变特异性免疫系统的原核类似物。
