Parray Zahoor Ahmad, Ahmad Faizan, Hassan Md Imtaiyaz, Ahmed Anwar, Almajhdi Fahad N, Malik Ajamaluddin, Hussain Tajamul, Islam Asimul
Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
Centre of Excellence in Biotechnology Research, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
Molecules. 2021 May 10;26(9):2807. doi: 10.3390/molecules26092807.
The intracellular environment is overcrowded with a range of molecules (small and large), all of which influence protein conformation. As a result, understanding how proteins fold and stay functional in such crowded conditions is essential. Several in vitro experiments have looked into the effects of macromolecular crowding on different proteins. However, there are hardly any reports regarding small molecular crowders used alone and in mixtures to observe their effects on the structure and stability of the proteins, which mimics of the cellular conditions. Here we investigate the effect of different mixtures of crowders, ethylene glycol (EG) and its polymer polyethylene glycol (PEG 400 Da) on the structural and thermal stability of myoglobin (Mb). Our results show that monomer (EG) has no significant effect on the structure of Mb, while the polymer disrupts its structure and decreases its stability. Conversely, the additive effect of crowders showed structural refolding of the protein to some extent. Moreover, the calorimetric binding studies of the protein showed very weak interactions with the mixture of crowders. Usually, we can assume that soft interactions induce structural perturbations while exclusion volume effects stabilize the protein structure; therefore, we hypothesize that under in vivo crowded conditions, both phenomena occur and maintain the stability and function of proteins.
细胞内环境充斥着一系列分子（大小各异），所有这些分子都会影响蛋白质的构象。因此，了解蛋白质在如此拥挤的条件下如何折叠并保持功能至关重要。一些体外实验研究了大分子拥挤对不同蛋白质的影响。然而，几乎没有关于单独使用小分子拥挤剂及其混合物来观察它们对蛋白质结构和稳定性影响的报道，而这种影响模拟了细胞环境。在这里，我们研究了拥挤剂乙二醇（EG）及其聚合物聚乙二醇（PEG 400 Da）的不同混合物对肌红蛋白（Mb）结构和热稳定性的影响。我们的结果表明，单体（EG）对Mb的结构没有显著影响，而聚合物会破坏其结构并降低其稳定性。相反，拥挤剂的加和效应在一定程度上使蛋白质发生了结构重折叠。此外，蛋白质的量热结合研究表明其与拥挤剂混合物的相互作用非常弱。通常，我们可以假设软相互作用会引起结构扰动，而排阻体积效应会稳定蛋白质结构；因此，我们推测在体内拥挤条件下，这两种现象都会发生并维持蛋白质的稳定性和功能。
