Mol C D, Arvai A S, Slupphaug G, Kavli B, Alseth I, Krokan H E, Tainer J A
Department of Molecular Biology, Scripps Research Institute, La Jolla, California 92037.
Cell. 1995 Mar 24;80(6):869-78. doi: 10.1016/0092-8674(95)90290-2.
Crystal structures of the DNA repair enzyme human uracil-DNA glycosylase (UDG), combined with mutational analysis, reveal the structural basis for the specificity of the enzyme. Within the classic alpha/beta fold of UDG, sequence-conserved residues form a positively charged, active-site groove the width of duplex DNA, at the C-terminal edge of the central four-stranded parallel beta sheet. In the UDG-6-aminouracil complex, uracil binds at the base of the groove within a rigid preformed pocket that confers selectivity for uracil over other bases by shape complementary and by main chain and Asn-204 side chain hydrogen bonds. Main chain nitrogen atoms are positioned to stabilize the oxyanion intermediate generated by His-268 acting via nucleophilic attack or general base mechanisms. Specific binding of uracil flipped out from a DNA duplex provides a structural mechanism for damaged base recognition.
DNA修复酶人尿嘧啶-DNA糖基化酶（UDG）的晶体结构，结合突变分析，揭示了该酶特异性的结构基础。在UDG经典的α/β折叠结构中，序列保守的残基在中央四链平行β折叠的C端边缘形成一个带正电荷的、双链DNA宽度的活性位点凹槽。在UDG-6-氨基尿嘧啶复合物中，尿嘧啶结合在凹槽底部一个刚性的预制口袋内，该口袋通过形状互补以及主链和Asn-204侧链氢键赋予对尿嘧啶相对于其他碱基的选择性。主链氮原子的位置可稳定由His-268通过亲核攻击或一般碱机制作用产生的氧阴离子中间体。从DNA双链中翻转出来的尿嘧啶的特异性结合为受损碱基识别提供了一种结构机制。
