a Faculty of Science, Department of Biology , University of Shahrekord , Shahrekord , P. O. Box. 115 , Iran.
b Institute of Biochemistry and Biophysics, University of Tehran , Tehran , Iran.
J Biomol Struct Dyn. 2017 Feb;35(2):435-448. doi: 10.1080/07391102.2016.1147984. Epub 2016 May 9.
Polyamines such as spermine can have interaction with protein. The aim of the present study was to investigate how spermine could influence the structure, thermal stability, and the activity of α-chymotrypsin. Kinetics, thermodynamics, molecular dynamics (MD), and docking simulations studies were conducted to investigate the effect of spermine on the activity and structure of α-Chymotrypsin (α-Chy) in 50 mM Tris-HCl buffer, with the pH 8, using different spectroscopic techniques as well as molecular docking and MD simulations. The stability and activity of α-Chy were increased in the presence of spermine. The results of the kinetic study showed that the activity of spermine was increased. Enzyme activation was accompanied by changes on the α-Chy conformation. Fluorescence intensity changes showed dynamic quenching during spermine binding. The fluorescence quenching of the α-Chy suggested the more polar location of Trp residues. Near-UV and Far-UV circular dichroism studies also demonstrated the transfer of Trp, Phe, and Tyr residues to a more flexible environment. The increase in the absorption of α-Chy in the presence of spermine was as a result of the formation of spermine-α-Chy complex. Molecular docking results revealed the presence of one binding site with a negative value for the Gibbs free energy of the binding of spermine to α-Chy. Docking study also revealed that van der Waals interactions and hydrogen bonds played a major role in stabilizing the complex.
多胺如 spermine 可以与蛋白质相互作用。本研究旨在探讨 spermine 如何影响 α-糜蛋白酶的结构、热稳定性和活性。通过动力学、热力学、分子动力学 (MD) 和对接模拟研究，在 50 mM Tris-HCl 缓冲液中，pH 值为 8，使用不同的光谱技术以及分子对接和 MD 模拟，研究了 spermine 对 α-糜蛋白酶 (α-Chy) 活性和结构的影响。在 spermine 的存在下，α-Chy 的稳定性和活性增加。动力学研究结果表明，spermine 的活性增加。酶的激活伴随着 α-Chy 构象的变化。荧光强度变化表明 spermine 结合时存在动态猝灭。α-Chy 的荧光猝灭表明色氨酸残基的极性位置发生了变化。近紫外和远紫外圆二色性研究也表明色氨酸、苯丙氨酸和酪氨酸残基转移到更灵活的环境中。在 spermine 存在下，α-Chy 的吸收增加是由于形成了 spermine-α-Chy 复合物。分子对接结果表明，存在一个结合位点，spermine 与 α-Chy 结合的吉布斯自由能为负值。对接研究还表明，范德华相互作用和氢键在稳定复合物方面起着重要作用。
