AlkB型蛋白是脫甲基酶,，被認(rèn)為通過氧化性去除DNA,、RNA和組蛋白上的甲基加合物而在DNA修復(fù)中扮演一個角色,。Yi等人確定了在與各種不同的被修飾的DNA形成的復(fù)合物中結(jié)晶了的AlkB氧化酶的結(jié)構(gòu),。
通過在厭氧條件下生長晶體,，然后將它們暴露于雙氧以啟動氧化,，他們捕捉到兩種不同的中間體,。第三種類型的中間體是另外利用計(jì)算分析確定的。這些結(jié)構(gòu)為這些酶怎樣進(jìn)行氧化脫甲基反應(yīng)提供了詳細(xì)的機(jī)制性見解,。（生物谷Bioon.com）
生物谷推薦英文摘要：
Nature doi:10.1038/nature09497
Iron-catalysed oxidation intermediates captured in a DNA repair dioxygenase
Chengqi Yi,Guifang Jia,Guanhua Hou,Qing Dai,Wen Zhang,Guanqun Zheng,Xing Jian,Cai-Guang Yang,Qiang Cui& Chuan He
Mononuclear iron-containing oxygenases conduct a diverse variety of oxidation functions in biology1, 2, including the oxidative demethylation of methylated nucleic acids and histones3, 4. Escherichia coli AlkB is the first such enzyme that was discovered to repair methylated nucleic acids5, 6, which are otherwise cytotoxic and/or mutagenic. AlkB human homologues are known to play pivotal roles in various processes7, 8, 9, 10, 11. Here we present structural characterization of oxidation intermediates for these demethylases. Using a chemical cross-linking strategy12, 13, complexes of AlkB–double stranded DNA (dsDNA) containing 1,N6-etheno adenine (εA), N3-methyl thymine (3-meT) and N3-methyl cytosine (3-meC) are stabilized and crystallized, respectively. Exposing these crystals, grown under anaerobic conditions containing iron(II) and α-ketoglutarate (αKG), to dioxygen initiates oxidation in crystallo. Glycol (from εA) and hemiaminal (from 3-meT) intermediates are captured; a zwitterionic intermediate (from 3-meC) is also proposed, based on crystallographic observations and computational analysis. The observation of these unprecedented intermediates provides direct support for the oxidative demethylation mechanism for these demethylases. This study also depicts a general mechanistic view of how a methyl group is oxidatively removed from different biological substrates.
