Sano H, Sager R
Eur J Biochem. 1980 Apr;105(3):471-80. doi: 10.1111/j.1432-1033.1980.tb04522.x.
DNA methyltransferase was purified 310-fold from a green alga, Chlamydomonas reinhardi vegetative cells. The native enzyme of molecular weight 55 000--58 000 catalyzed the transfer of methyl groups from S-adenosylmethionine to the 5 position of cytosine in DNA. Native DNA accepted methyl groups 10-fold more than did denatured DNA. The sequence specificity analysis of methylated deoxycytidine in vitro revealed that the enzyme introduces methyl groups preferentially into sequences containing 5'd(T-mC-R)3'. Kinetic analysis of the reaction indicated that the enzyme obeys a random sequential mechanism. The extent of saturation with methyl groups depends upon the species from which the DNA was obtained. Kinetic analysis of the reaction catalyzed by RNA polymerase II has indicated that DNA methylation decreases the rate of initiation of RNA synthesis, but does not affect the rate of RNA chain elongation.
从绿藻莱茵衣藻的营养细胞中纯化出了310倍的DNA甲基转移酶。分子量为55000 - 58000的天然酶催化甲基从S - 腺苷甲硫氨酸转移到DNA中胞嘧啶的5位。天然DNA接受甲基的能力比变性DNA高10倍。体外甲基化脱氧胞苷的序列特异性分析表明，该酶优先将甲基引入含有5'd(T - mC - R)3'的序列中。该反应的动力学分析表明，该酶遵循随机顺序机制。甲基化饱和程度取决于DNA来源的物种。RNA聚合酶II催化反应的动力学分析表明，DNA甲基化降低了RNA合成起始速率，但不影响RNA链延伸速率。
