Schluckebier G, Labahn J, Granzin J, Schildkraut I, Saenger W
Freie Universität Berlin, Institut für Kristallographie, Germany.
Gene. 1995 May 19;157(1-2):131-4. doi: 10.1016/0378-1119(94)00690-t.
The crystal structures of the DNA-N6-adenine-methyltransferase M.TaqI, in complexes with the cofactor S-adenosyl-L-methionine (AdoMet) and the competitive inhibitor sinefungin (Sf) show identical folding of the polypeptide chains into two domains. The N-terminal domain carries the cofactor-binding site, the C-terminal domain is thought to be implicated in sequence-specific DNA binding. Model building of the M.TaqI-DNA complex suggests that the adenine to be methylated swings out of the double helix as found previously in the cytosine-C5-MTase HhaI DNA co-crystal structure. A torsion of the methionine moiety of the cofactor is required to bring the methyl group within reach of the swung-out base and allow methyl group transfer.
DNA - N6 - 腺嘌呤甲基转移酶M.TaqI与辅因子S - 腺苷 - L - 甲硫氨酸（AdoMet）及竞争性抑制剂杀稻瘟菌素（Sf）形成的复合物的晶体结构显示，多肽链折叠成两个结构域的方式相同。N端结构域含有辅因子结合位点，C端结构域被认为与序列特异性DNA结合有关。M.TaqI - DNA复合物的模型构建表明，待甲基化的腺嘌呤会如先前在胞嘧啶 - C5 - 甲基转移酶HhaI DNA共晶体结构中所发现的那样，从双螺旋中摆动出来。需要辅因子甲硫氨酸部分发生扭转，以使甲基能够接触到摆动出来的碱基并实现甲基转移。
