Heme binds to an intrinsically disordered region of Bach2 and alters its conformation
Heme binds to an intrinsically disordered region of Bach2 and alters its conformation
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血红素与 Bach2 本质上无序的区域结合并改变其构象
DOI：
10.1016/j.abb.2014.11.005
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发表时间：
2014
影响因子：
3.9
通讯作者：
and K. Igarashi
中科院分区：
文献类型：
--
作者：
M. Watanabe-Matsui;T. Matsumoto;T. Matsui;M. Ikeda-Saito;A. Muto;K. Murayama;and K. Igarashi
转录抑制因子Bach2调节体液和细胞免疫，包括抗体类别转换。它具有一个基本的亮氨酸拉链结构域，可以介导DNA结合。血红素在体外抑制Bach2的DNA结合活性，并诱导B细胞中Bach2的降解。然而，血红素-Bach2相互作用的结构基础尚未确定。光谱分析表明，Bach2331-520是血红素结合结构域，因为它包括三个已知对血红素结合重要的Cys-Pro基序。血红素滴定实验证明存在5配位和6配位的血红素结合模式。圆二色谱测量表明，Bach2331-520主要以无规卷曲构象存在。然而，动态光散射分析表明，与未结合的Bach2331-520相比，血红素与Bach2331-520结合后，该区域在较低的温度下变性。此外，小角X射线散射和化学修饰分析表明，血红素结合导致非结构区域内的构象变化。293T细胞中基于GAL4的荧光素酶分析表明，血红素改变了Bach2331-520介导的蛋白质相互作用。这些观察表明，Bach2的非结构化区域对于血红素结合，从而对其功能调节是重要的。
The transcriptional repressor Bach2 regulates humoral and cellular immunity, including antibody class switching. It possesses a basic leucine zipper domain that mediates DNA binding. Heme inhibits the DNA-binding activity of Bach2in vitroand induces the degradation of Bach2 in B cells. However, the structural basis of the heme–Bach2 interaction has not been identified. Spectroscopic analyses revealed that Bach2331–520is the heme-binding domain, as it includes three Cys-Pro motifs known to be important for heme binding. Heme-titration experiments demonstrated the presence of 5- and 6-coordinated heme-binding modes. Circular dichroism measurements indicated that Bach2331–520exists mostly in a random-coil conformation. However, dynamic light scattering analyses showed that, upon heme binding to Bach2331–520, this region becomes denatured at a lower temperature, as compared with unbound Bach2331–520. In addition, small-angle X-ray scattering and chemical modification analyses revealed that heme binding induces conformational alterations within the unstructured region. A GAL4-based luciferase assay in 293T cells showed that heme alters the protein interactions mediated by Bach2331–520. These observations suggested that the unstructured region of Bach2 is important for heme binding, and consequently for its functional regulation.