AbstractWe have studied the adenosine binding specificities of two bacterial DNA methyltransferases, Taq methyltransferase (M.TaqI), and HhaI methyltransferase (M.HhaI). While they have similar cofactor binding pocket interactions, experimental data showed different specificity for novel S‐nucleobase‐l‐methionine cofactors (SNMs; N=guanosyl, cytidyl, uridyl). Protein dynamics corroborate the experimental data on the cofactor specificities. For M.TaqI the specificity for S‐adenosyl‐l‐methionine (SAM) is governed by the tight binding on the nucleoside part of the cofactor, while for M.HhaI the degree of freedom of the nucleoside chain allows the acceptance of other bases. The experimental data prove catalytically productive methylation by the M.HhaI binding pocket for all the SNMs. Our results suggest a new route for successful design of unnatural SNM analogues for methyltransferases as a tool for cofactor engineering.
摘要 我们研究了两种细菌 DNA 甲基转移酶--Taq 甲基转移酶(M.TaqI)和 HhaI 甲基转移酶(M.HhaI)--的腺苷结合特异性。虽然它们具有相似的辅助因子结合袋相互作用,但实验数据显示它们对新型 S-核糖基-l-蛋氨酸辅助因子(SNMs;N=鸟苷基、胞苷基、尿苷基)具有不同的特异性。蛋白质动力学证实了辅因子特异性的实验数据。对于 M.TaqI,S-腺苷-l-蛋氨酸(SAM)的特异性取决于与辅因子核苷部分的紧密结合,而对于 M.HhaI,核苷链的自由度允许接受其他碱基。实验数据证明,M.HhaI 结合袋对所有 SNM 都有催化甲基化的作用。我们的研究结果为成功设计甲基转移酶的非天然 SNM 类似物提供了一条新途径,可作为辅助因子工程的工具。