Kravets A N, Solonin A S, Zakharova M V, Tarutina Z E
Mol Gen Mikrobiol Virusol. 1992 Jul-Aug(7-8):4-7.
Over 60 producing strains of restriction endonucleases type II have been found among 500 different strains, mostly Enterobacteriaceae. The strain Citrobacter freundii 4111 produces restriction endonuclease CfrBI, a new isoschisomer of StyI. The genes of the restriction-modification system CfrBI were located on the multicopy plasmid pZE8 containing the Co1E1-type replicon and cloned to E. coli K802. The deletion variant of 3.2-kb pZE8 which contains intact restriction-modification and a DNA fragment responsible for autonomous plasmid replication was selected among the recombinant plasmids. The strain with higher R. CfrBI production (at least 10,000,000 U/g cells, which is 500-fold higher than the wild strain) was constructed.
在500种不同菌株中发现了60多种II型限制性内切酶产生菌株，其中大部分是肠杆菌科细菌。弗氏柠檬酸杆菌4111菌株产生限制性内切酶CfrBI，它是StyI的一种新的同裂酶。限制性修饰系统CfrBI的基因位于含有ColE1型复制子的多拷贝质粒pZE8上，并克隆到大肠杆菌K802中。在重组质粒中筛选出了3.2-kb pZE8的缺失变体，它含有完整的限制性修饰和负责质粒自主复制的DNA片段。构建了具有更高CfrBI产量的菌株（至少10000000 U/g细胞，比野生菌株高500倍）。
