<h3>Title</h3>
<h3>Crowding-induced effects on the stability of ubiquitin-family proteins</h3>
<p><strong><span style="text-decoration: underline;">Abstract</span> :</strong></p>
<p>The interior of the cell is highly complex and crowded with various macromolecules.<sup>1</sup> Such complex environment can alter thermodynamic, structural and functional properties of proteins as compared to dilute buffer conditions. To study the effect of crowding on protein stability <em>in vitro</em>, researchers often use synthetic polymers such as dextran, polyethylene glycol, ficoll, etc. as crowding agents.<sup>2</sup> These cosolutes can influence the stability of the protein by hard-core repulsions (crowding) and soft chemical interactions (sticking).<sup>3</sup> It has been found that cosolute-induced effects on proteins depend upon the size and shape of the cosolute as well as on the nature of the test protein.<sup>4,5</sup> To understand the factors influencing the cosolute-induced effects, we use two well-studied structurally homologous proteins of similar sizes, ubiquitin and N-del SUMO-1 (SUMO-1 protein without its unstructured N-terminal tail). From thermal and chemical denaturation experiments performed on ubiquitin, we observed that PEG-20000 destabilizes the protein. The extent of destabilization depends on size and concentration of the PEG polymer. However, N-del SUMO-1 was found to start aggregating within few minutes on addition of 15% PEG-20000 at pH 7.4. In contrast, another cosolute dextran-20000 is found to increase the stability of ubiquitin. The effect of dextran on SUMO-1 is currently being studied.</p>
<p> References:</p>
<ol>
<li>Zimmerman, S. B., and S. O. Trach<em>. J. Mol. Biol</em>.1999, 222, 599–620.</li>
<li>Zhou, H. X., G. Rivas, and A. P. Minton. <em> Rev. Biophys</em>. 2008, 37, 375–397.</li>
<li>Grasso, D. M.; Sciacca, M. F. M.; Milardi, D.; Pappalardo, M.;La Rosa, C. <em> Therm. Anal. Calorim.</em> 2006, 86, 311−314.</li>
<li>Nilimesh Das and Pratik Sen <em>The Journal of Physical Chemistry B</em>2020, 124, 5858-5871</li>
<li>Nilimesh Das and Pratik Sen <em> J. Biol. Macromol.</em> 2019, 141, 843-854.</li>
</ol>