The ChiS-Family DNA-Binding Domain Contains a Cryptic Helix-Turn-Helix Variant.
The ChiS-Family DNA-Binding Domain Contains a Cryptic Helix-Turn-Helix Variant.
复制标题
DOI：
10.1128/mbio.03287-20
复制
发表时间：
2021-03-16
期刊：
影响因子：
6.4
通讯作者：
Dalia AB
中科院分区：
文献类型：
--
作者：
Klancher CA;Minasov G;Podicheti R;Rusch DB;Dalia TN;Satchell KJF;Neiditch MB;Dalia AB
调节基因表达在生命的所有领域都是必不可少的。这一过程通常由DNA结合转录因子的活性促进。序列特异性DNA结合结构域（DBD）在生命的所有领域都是保守的。这些蛋白质执行多种细胞功能，并且已经描述了许多允许序列特异性DNA结合的不同结构域，包括普遍存在的螺旋-转角-螺旋（HTH）结构域。在兼性病原体霍乱弧菌中，几丁质传感器ChiS是一种转录调节因子，对于这种生物在其海洋水库中的生存至关重要。我们最近发现ChiS在其C末端含有一个隐蔽的DBD。该结构域与任何已知的DBD都不同源，但它是存在于其他细菌蛋白中的保守结构域。在这里，我们提出的晶体结构的ChiS DBD的分辨率为1.28 μ m。我们发现，ChiS DBD包含一个HTH结构域，在结构上类似于其他DNA结合蛋白，如LacI阻遏物。然而，在ChiS DBD中观察到的一个显著差异是HTH的典型紧转角被包含β折叠的插入物取代，我们称之为螺旋-折叠-螺旋的变体。通过系统诱变所有带正电荷的残基内的ChiS DBD，我们表明，内和接近ChiS螺旋片螺旋的残基是DNA结合的关键。最后，通过系统发育分析，我们发现，在不同的变形菌蛋白质，表现出不同的结构域架构的ChiS DBD。总之，这些结果表明，这里描述的结构代表的原型成员的ChiS-家庭的DBD。
Regulating gene expression is essential in all domains of life. This process is commonly facilitated by the activity of DNA-binding transcription factors. Sequence-specific DNA-binding domains (DBDs) are conserved in all domains of life. These proteins carry out a variety of cellular functions, and there are a number of distinct structural domains already described that allow for sequence-specific DNA binding, including the ubiquitous helix-turn-helix (HTH) domain. In the facultative pathogen Vibrio cholerae, the chitin sensor ChiS is a transcriptional regulator that is critical for the survival of this organism in its marine reservoir. We recently showed that ChiS contains a cryptic DBD in its C terminus. This domain is not homologous to any known DBD, but it is a conserved domain present in other bacterial proteins. Here, we present the crystal structure of the ChiS DBD at a resolution of 1.28 Å. We find that the ChiS DBD contains an HTH domain that is structurally similar to those found in other DNA-binding proteins, like the LacI repressor. However, one striking difference observed in the ChiS DBD is that the canonical tight turn of the HTH is replaced with an insertion containing a β-sheet, a variant which we term the helix-sheet-helix. Through systematic mutagenesis of all positively charged residues within the ChiS DBD, we show that residues within and proximal to the ChiS helix-sheet-helix are critical for DNA binding. Finally, through phylogenetic analyses we show that the ChiS DBD is found in diverse proteobacterial proteins that exhibit distinct domain architectures. Together, these results suggest that the structure described here represents the prototypical member of the ChiS-family of DBDs.