Department of Biotechnology, Haldia Institute of Technology, PO-HIT, Dist-Purba, Medinipur, 721657, West Bengal, India.
Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India.
Protein J. 2018 Apr;37(2):103-112. doi: 10.1007/s10930-018-9762-1.
SarA, a pleiotropic transcription regulator, is encoded by Staphylococcus aureus, a pathogenic bacterium. The expression of many virulence and non-virulence genes in S. aureus is modulated by this regulator. Structural studies have shown it to be a winged-helix DNA-binding protein carrying two monomers. Each SarA monomer is composed of five α-helices (α1-α5), three β-strands (β1-β3) and multiple loops. The putative DNA binding region of SarA is constituted with α3, α4, β2, and β3, whereas, its dimerization seems to occur using α1, α2, and α5. Interestingly, many SarA-like proteins are dimeric and use three or more helices for their dimerization. To clearly understand the roles of helix α1 in the dimerization, we have constructed and purified a SarA mutant (Δα1) that lacks helix α1. Our in-depth studies with Δα1 indicate that the helix α1 is critical for preserving the structure, DNA binding activity and thermodynamic stability of SarA. However, the helix has little affected its dimerization ability. Possible reasons for such anomaly have been discussed at length.
SarA 是一种多效转录调节因子，由致病性细菌金黄色葡萄球菌编码。该调节因子调控金黄色葡萄球菌中许多毒力基因和非毒力基因的表达。结构研究表明，它是一种具有两个单体的翼状螺旋 DNA 结合蛋白。每个 SarA 单体由五个α螺旋（α1-α5）、三个β链（β1-β3）和多个环组成。SarA 的假定 DNA 结合区由α3、α4、β2 和β3 组成，而其二聚化似乎使用α1、α2 和α5 发生。有趣的是，许多 SarA 样蛋白是二聚体，并用三个或更多的螺旋进行二聚化。为了清楚地了解螺旋 α1 在二聚化中的作用，我们构建并纯化了缺失螺旋 α1 的 SarA 突变体（Δα1）。我们对Δα1 的深入研究表明，螺旋 α1 对于保持 SarA 的结构、DNA 结合活性和热力学稳定性至关重要。然而，该螺旋对其二聚化能力几乎没有影响。对于这种异常现象，我们进行了详细的讨论。
