[大肠杆菌C中DNA胞嘧啶甲基转移酶的分离及性质]

[Isolation and properties of DNA-cytosine methyltransferase from Escherichia coli C].

作者信息

Bogdarina I G, Bur'ianov Ia I, Baev A A

出版信息

Mol Biol (Mosk). 1979 Mar-Apr;13(2):281-91.

Abstract

The method of isolation and partial purification of DNA-cytosine-methyltransferase (DC-methylase) from E. coli C is described. The enzyme underwent approximately 100-fold purification. The obtained preparation of DC-methylase can be additionally considerably purified by sedimentation in sucrose gradient. Native molecular weight of DC-methylase from E. coli C. is 70,000. The activity of enzyme does not depend on the Mg2+ ions. DC-methylase E. coli C provides DNA of lambda phage in vitro with full resistance against restriction endonuclease EcoRII. In DNA methylated by DC-methylase the modified cytosine, mainly in C-MC and C-MC-T sequences, corresponds to the pyrimidine sequences of specific site EcoRII. DNA of lambda.B phage contains approximately 80 sites for modification by DC-methylase E. coli C. The results obtained point to the same specificity in vitro of DNA-cytosine-methylase E. coli C and DNA-methylase EcoRII.

摘要

本文描述了从大肠杆菌C中分离和部分纯化DNA-胞嘧啶甲基转移酶（DC-甲基化酶）的方法。该酶经过了约100倍的纯化。所得的DC-甲基化酶制剂可通过蔗糖梯度沉降进一步显著纯化。大肠杆菌C的DC-甲基化酶的天然分子量为70,000。该酶的活性不依赖于Mg2+离子。大肠杆菌C的DC-甲基化酶在体外使λ噬菌体的DNA对限制性内切酶EcoRII具有完全抗性。在由DC-甲基化酶甲基化的DNA中，修饰的胞嘧啶主要存在于C-MC和C-MC-T序列中，与特定位点EcoRII的嘧啶序列相对应。λ.B噬菌体的DNA含有约80个可被大肠杆菌C的DC-甲基化酶修饰的位点。所得结果表明大肠杆菌C的DNA-胞嘧啶甲基化酶和EcoRII DNA-甲基化酶在体外具有相同的特异性。