ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India.
Center for Plant Molecular Biology Division, CSIR-NBRI, Lucknow, India.
PLoS One. 2020 Mar 5;15(3):e0229216. doi: 10.1371/journal.pone.0229216. eCollection 2020.
RNA biogenesis and mRNA transport are an intricate process for every eukaryotic cell. SAGA, a transcriptional coactivator and TREX-2 are the two major complexes participate in this process. Sus1 is a transcription export factor and part of both the SAGA and the TREX-2 complex. The competitive exchange of Sus1 molecule between SAGA and TREX-2 complex modulates their function which is credited to structural plasticity of Sus1. Here, we portray the biophysical characterization of Sus1 from S. cerevisiae. The recombinant Sus1 is a α-helical structure which is stable at various pH conditions. We reported the α-helix to β-sheet transition at the low pH as well as at high pH. Sus1 showed 50% reduction in the fluorescence intensity at pH-2 as compared to native protein. The fluorescence studies demonstrated the unfolding of tertiary structure of the protein with variation in pH as compared to neutral pH. The same results were obtained in the ANS binding and acrylamide quenching studies. Similarly, the secondary structure of the Sus1 was found to be stable till 55% alcohol concentration while tertiary structure was stable up to 20% alcohol concentration. Further increase in the alcohol concentration destabilizes the secondary as well as tertiary structure. The 300 mM concentration of ammonium sulfate also stabilizes the secondary structure of the protein. The structural characterization of this protein is expected to unfold the process of the transportation of the mRNA with cooperation of different proteins.
RNA 生物发生和 mRNA 运输是每个真核细胞的复杂过程。SAGA 是一种转录共激活因子，TREX-2 是参与该过程的两个主要复合物之一。Sus1 是一种转录输出因子，是 SAGA 和 TREX-2 复合物的一部分。Sus1 分子在 SAGA 和 TREX-2 复合物之间的竞争交换调节它们的功能，这归因于 Sus1 的结构可塑性。在这里，我们描绘了来自酿酒酵母的 Sus1 的生物物理特性。重组 Sus1 是一种 α-螺旋结构，在各种 pH 条件下都很稳定。我们报告了在低 pH 以及高 pH 条件下 α-螺旋向 β-折叠的转变。与天然蛋白相比，Sus1 在 pH-2 时的荧光强度降低了 50%。荧光研究表明，与中性 pH 相比，pH 变化导致蛋白质的三级结构展开。在 ANS 结合和丙烯酰胺猝灭研究中也得到了相同的结果。同样，Sus1 的二级结构在 55%酒精浓度下保持稳定，而三级结构在 20%酒精浓度下保持稳定。进一步增加酒精浓度会使二级和三级结构不稳定。300mM 浓度的硫酸铵也能稳定蛋白质的二级结构。该蛋白质的结构特征有望阐明在不同蛋白质的合作下 mRNA 运输的过程。
