Malygin Ernst G, Evdokimov Alexey A, Hattman Stanley
State Research Center of Virology and Biotechnology Vector, Novosibirsk, Russia.
Biol Chem. 2009 Sep;390(9):835-44. doi: 10.1515/BC.2009.082.
DNA methyltransferases (MTases) are enzymes that carry out post-replicative sequence-specific modifications. The initial experimental data on the structure and kinetic characteristics of the EcoRI MTase led to the paradigm that type II systems comprise dimeric endonucleases and monomeric MTases. In retrospect, this was logical because, while the biological substrate of the restriction endonuclease is two-fold symmetrical, the in vivo substrate for the MTase is generally hemi-methylated and, hence, inherently asymmetric. Thus, the paradigm was extended to include all DNA MTases except the more complex bifunctional type I and type III enzymes. Nevertheless, a gradual enlightenment grew over the last decade that has changed the accepted view on the structure of DNA MTases. These results necessitate a more complex view of the structure and function of these important enzymes.
DNA甲基转移酶（MTases）是一类进行复制后序列特异性修饰的酶。关于EcoRI甲基转移酶结构和动力学特性的最初实验数据形成了一种范式，即II型系统由二聚体内切核酸酶和单体甲基转移酶组成。回顾起来，这是合乎逻辑的，因为虽然限制性内切核酸酶的生物学底物是二重对称的，但甲基转移酶在体内的底物通常是半甲基化的，因此本质上是不对称的。因此，该范式扩展到包括除更复杂的双功能I型和III型酶之外的所有DNA甲基转移酶。然而，在过去十年中逐渐有了新的认识，这改变了人们对DNA甲基转移酶结构的公认观点。这些结果需要对这些重要酶的结构和功能有更复杂的认识。
