Solution structure, mutagenesis, and NH exchange studies of the MutT enzyme–Mg2+-8-oxo-dGMP complex
作者:M.A. Massiah、V. Saraswat、H.F. Azurmendi、A.S. Mildvan
DOI:10.1016/j.molstruc.2003.12.060
日期:2004.8
(37-fold), suggesting that Asn-119 functioned both as a hydrogen bond donor to C8O, and a hydrogen bond acceptor from N7H of 8-oxo-dGMP, while aspartate at position −119 functioned as an acceptor of a single hydrogen bond. Much smaller weakening effects (0.3–0.4 kcal/mol) on the binding of dGMP and dAMP were found, indicating specific hydrogen bonding of Asn-119 to 8-oxo-dGMP. While formation of the wild
摘要 来自大肠杆菌的 MutT 焦磷酸水解酶(129 个残基)催化三磷酸核苷 (NTP) 的水解,包括 8-oxo-dGTP,通过在 Pβ 上的取代,产生 NMP 和焦磷酸。产物 8-oxo-dGMP 是一种异常紧密结合的缓慢交换抑制剂,KD=52 nM,(ΔG°=−9.8 kcal/mol),比 dGMP 的结合(ΔG°= −3.7 kcal/mol)。尽管不利的 -TΔS°结合(+22 kcal/mol),但对 8-oxo-dGMP 的更高亲和力源于更有利的 ΔH 结合(-32 kcal/mol)。MutT-Mg2+-8-oxo-dGMP 复合物的溶液结构显示出狭窄的疏水性核苷酸结合裂缝,在少数极性残基中具有 Asn-119 和 Arg-78。N119A、N119D、R78K 和 R78A 单突变,以及 R78K+N119A 双突变都显示出基本完整的活性位点,基于 dGTP 水解动力学参数和