Nesterenko V F, Bur'ianov Ia I, Baev A A
Biokhimiia. 1979 Jan;44(1):130-41.
DNA-cytosine-methylase I was isolated and purified to homogeneity. The yield made up to about 30% of total activity. The enzyme molecular weight as determined by centrifugation in a sucrose gradient, by gel filtration and by electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate was found to be 45,000. The Michaelis constant was 1,8 . 10(-6) M for SAM and 2 . 10(-4) M for DNA. DNA-cytosine-methylase I modifies phage lambda DNA in 60 sites. This modification does not protect DNA from the effects of restriction endonucleases HpaII and BsuRI. The enzyme methylates DNA in the nucleotide sequence: 5'...Pur-MC-C-G-G-Pyr...3'.
DNA胞嘧啶甲基化酶I被分离纯化至同质。产量约占总活性的30%。通过在蔗糖梯度中离心、凝胶过滤以及在十二烷基硫酸钠存在下的聚丙烯酰胺凝胶电泳测定，该酶的分子量为45,000。对SAM的米氏常数为1.8×10⁻⁶ M，对DNA的米氏常数为2×10⁻⁴ M。DNA胞嘧啶甲基化酶I在60个位点修饰噬菌体λ DNA。这种修饰不能保护DNA免受限制性内切酶HpaII和BsuRI的作用。该酶在核苷酸序列5'...嘌呤 - 甲基胞嘧啶 - 胞嘧啶 - 鸟嘌呤 - 鸟嘌呤 - 嘧啶...3'中使DNA甲基化。
