Crystal structure of E47 neuroD1/Beta2 bHLH domain DNA complex: Heterodimer selectivity and DNA recognition
Crystal structure of E47 neuroD1/Beta2 bHLH domain DNA complex: Heterodimer selectivity and DNA recognition
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DOI：
10.1021/bi701527r
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发表时间：
2008-01-08
期刊：
影响因子：
2.9
通讯作者：
Rose, Robert B.
中科院分区：
文献类型：
--
作者：
Longo, Antonella;Guanga, Gerald P.;Rose, Robert B.
普遍存在的I类碱性螺旋-环-螺旋（bHLH）因子E47与多种组织特异性11类bHLH蛋白形成异二聚体，调节不同的分化途径。为了确定如何选择I类-II类异二聚体伴侣，我们确定了与胰岛素启动子E-box序列复合的E47-NeuroD1-bHLH二聚体的晶体结构。E47-NeuroD1的bHLH结构域的纯化表明E47异二聚体在溶液中是稳定的。异二聚体中E47和NeuroD 1之间的相互作用与同二聚体中E47单体之间的相互作用相当，包括氢键、埋置的疏水性表面和包装相互作用。这与E47-NeuroD1异源二聚体由于NeuroD1同源二聚体的不稳定性而受到青睐的模型一致。尽管E47-NeuroD1在胰岛素基因启动子内的E-box序列（CATCTG）上唯一定向，但未观察到与该E-box序列内的中心碱基对的直接接触。我们建议，一致的域运动允许E47在溶液中形成特定的基础接触。NeuroD1被神经原性特异性残基His115通过额外的磷酸骨架相互作用抑制采用相同的碱基接触。在启动子上定位E47-NeuroD1可能会促进启动转录所必需的蛋白质-蛋白质接触。
The ubiquitous class I basic helix-loop-helix (bHLH) factor E47 forms heterodimers with multiple tissue specific class 11 bHLH proteins to. regulate distinct differentiation pathways. In order to define how class I- class II heterodimer partners are selected, we determined the crystal structure of the E47-NeuroD1-bHLH dimer in complex with the insulin promoter E-box sequence. Purification of the bHLH domain of E47-NeuroD1 indicates that E47 heterodimers are stable in solution. The interactions between E47 and NeuroD1 in the heterodimer are comparable to the interactions between E47 monomers in the homodimer, including hydrogen bonding, buried hydrophobic surface, and packing interactions. This is consistent with a model in which E47-NeuroD1 heterodimers are favored due to the instability of NeuroD1 homodimers. Although E47-NeuroD1 is oriented uniquely on the E-box sequence (CATCTG) within the promoter of the insulin gene, no direct contacts are observed with the central base pairs within this E-box sequence. We propose that concerted domain motions allow E47 to form specific base contacts in solution. NeuroD1 is restrained from adopting the same base contacts by an additional phosphate backbone interaction by the neurogenic-specific residue His115. Orienting E47-NeuroD1 on promoters may foster protein-protein contacts essential to initiate transcription.