al-Awadhi S, Welch S G, Smith K E, Williams R A
Department of Biochemistry, Faculty of Basic Medical Science, St Bartholomew's, Queen Mary and Westfield College, University of London, UK.
FEMS Microbiol Lett. 1998 Mar 15;160(2):205-8. doi: 10.1111/j.1574-6968.1998.tb12912.x.
Isolates of thermophilic bacteria from desert soil in Kuwait, heavily contaminated with crude oil, have been screened for the presence of restriction endonuclease activity. One of the isolates (B7S), identified as Bacillus stearothermophilus, showed a high level of restriction endonuclease activity when a cell-free extract was incubated with lambda bacteriophage DNA at 65 degrees C. A type II restriction endonuclease (BstB7SI) has been partially purified from this isolate. BstB7SI recognises the six-base sequence RCCGGY (R = A or G; Y = T or C) and hydrolyses the phosphodiester bond in both strands of the DNA substrate between the first and second bases of the recognition sequence 5'-R decreases CCGGY-3'producing four-base 5' overhangs. BstB7SI is therefore an isoschizomer of the mesophilic prototype restriction endonuclease Cfr10I. BstB7SI has a pH optimum of 9.7, requires 10 mM MgCl2 and 75 mM NaCl for maximum activity, and retains full enzyme activity when incubated for 5 min at temperatures up to 70 degrees C.
从科威特被原油严重污染的沙漠土壤中分离出的嗜热细菌菌株，已针对限制内切酶活性的存在进行了筛选。其中一个菌株（B7S）被鉴定为嗜热脂肪芽孢杆菌，当无细胞提取物在65℃下与λ噬菌体DNA一起孵育时，显示出高水平的限制内切酶活性。已从该菌株中部分纯化出一种II型限制内切酶（BstB7SI）。BstB7SI识别六碱基序列RCCGGY（R = A或G；Y = T或C），并水解DNA底物两条链中识别序列5'-RCCGGY-3'的第一个和第二个碱基之间的磷酸二酯键，产生四碱基5'突出端。因此，BstB7SI是嗜温原型限制内切酶Cfr10I的同裂酶。BstB7SI的最适pH为9.7，最大活性需要10 mM MgCl2和75 mM NaCl，并且在高达70℃的温度下孵育5分钟时仍保留全部酶活性。
