Structure of the N6-adenine DNA methyltransferase M•Taql in complex with DNA and a cofactor analog
Structure of the N6-adenine DNA methyltransferase M•Taql in complex with DNA and a cofactor analog
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DOI：
10.1038/84104
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发表时间：
2001-02-01
期刊：
影响因子：
--
通讯作者：
Weinhold, E
中科院分区：
文献类型：
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作者：
Goedecke, K;Pignot, M;Weinhold, E
N6-腺嘌呤DNA甲基转移酶M-TaqI与特定DNA和非反应性辅因子类似物复合的2.0埃晶体结构揭示了螺旋外靶碱基的先前未被认识到的稳定性。为了催化甲基从辅因子S-腺苷-L-甲硫氨酸转移到双链DNA序列5 '-TCGA-3'内腺嘌呤的C-氨基，将靶核苷旋转出DNA螺旋。通过在靶碱基对位置处垂直于DNA螺旋轴的DNA压缩和在链间重新堆叠位置中的配偶体碱基胸腺嘧啶的重新定位来实现螺旋外构象的稳定，在该位置处，它将与内螺旋靶腺嘌呤空间重叠。螺旋外靶腺嘌呤在活性位点被特异性识别，腺嘌呤的6-氨基与Asn 105和Pro 106形成两个氢键，Asn 105和Pro 106都属于N6-腺嘌呤DNA甲基转移酶的保守催化基序IV，这些氢键似乎增加了腺嘌呤的N6原子的部分负电荷，并激活它对腺嘌呤的甲基进行直接亲核攻击。辅因子
The 2.0 Angstrom crystal structure of the N6-adenine DNA methyltransferase M-TaqI in complex with specific DNA and a nonreactive cofactor analog reveals a previously unrecognized stabilization of the extrahelical target base. To catalyze the transfer of the methyl group from the cofactor S-adenosyl-L-methionine to the C-amino group of adenine within the double-stranded DNA sequence 5'-TCGA-3', the target nucleoside is rotated out of the DNA helix. Stabilization of the extrahelical conformation is achieved by DNA compression perpendicular to the DNA helix axis at the target base pair position and relocation of the partner base thymine in an interstrand re-stacked position, where it would sterically overlap with an innerhelical target adenine. The extrahelical target adenine Is specifically recognized in the active site, and the 6-amino group of adenine donates two hydrogen bonds to Asn 105 and Pro 106, which both belong to the conserved catalytic motif IV of N6-adenine DNA methyltransferases, These hydrogen bonds appear to increase the partial negative charge of the N6 atom of adenine and activate it for direct nucleophilic attack on the methyl group of the cofactor.