Features of a Smad3 MH1-DNA complex -: Roles of water and zinc in DNA binding
Features of a Smad3 MH1-DNA complex -: Roles of water and zinc in DNA binding
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DOI：
10.1074/jbc.c300134200
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发表时间：
2003-05-30
影响因子：
4.8
通讯作者：
Shi, YG
中科院分区：
文献类型：
--
作者：
Chai, JJ;Wu, JW;Shi, YG
Smad蛋白家族介导生长因子- β信号从细胞膜到细胞核的转化。在细胞核中，Smads通过直接结合特定的DNA序列并调节配体反应基因的表达而发挥转录因子的作用。先前在2.8埃分辨率下的结构分析揭示了Smad MH1结构域的一种新的dna结合模式，但不能准确分配蛋白质- dna相互作用的细微特征。以2.4埃的分辨率测定了与回文DNA序列结合的smad3mh1结构域的晶体结构，揭示了水分子令人惊讶的重要作用。DNA结合基序（一个保守的11-残基-发夹）在DNA主槽中的不对称位置由7个有序的水分子支撑。这些水分子与DNA碱基、DNA磷酸盐骨架和几个关键的Smad3残基形成特定的氢键。此外，发现MH1结构域包含一个结合锌原子，使用Smad蛋白中的四个不变残基，三个半胱氨酸和一个组氨酸。去除锌原子导致DNA结合活性受损。这些结果将Smad MH1结构域定义为具有独特DNA结合特性的锌协调模块。
The Smad family of proteins mediates transforming growth factor-beta signaling from cell membrane to the nucleus. In the nucleus, Smads serve as transcription factors by directly binding to specific DNA sequences and regulating the expression of ligand-response genes. A previous structural analysis, at 2.8-Angstrom resolution, revealed a novel DNA-binding mode for the Smad MH1 domain but did not allow accurate assignment of the fines features of protein-DNA interactions. The crystal structure of a Smad3 MH1 domain bound to a palindromic DNA sequence, determined at 2.4-Angstrom resolution, reveals a surprisingly important role for water molecules. The asymmetric placement of the DNA-binding motif (a conserved 11-residue beta-hairpin) in the major groove of DNA is buttressed by seven well ordered water molecules. These water molecules make specific hydrogen bonds to the DNA bases, the DNA phosphate backbones, and several critical Smad3 residues. In addition, the MH1 domain is found to contain a bound zinc atom using four invariant residues among Smad proteins, three cysteines and one histidine. Removal of the zinc atom results in compromised DNA binding activity. These results define the Smad MH1 domain as a zinc-coordinating module that exhibits unique DNA binding properties.