Varshney Ankita, Ahmad Basir, Khan Rizwan Hasan
Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, U.P. 202002, India.
Int J Biol Macromol. 2008 Jun 1;42(5):483-90. doi: 10.1016/j.ijbiomac.2008.03.004. Epub 2008 Mar 26.
This study was undertaken to investigate the influence of fatty acid binding on the unfolding of HSA and how the fatty acid molecules can influence and/or compete with other ligand molecules bound to the protein. The equilibrium unfolding of fatted and fatty acid free HSA was measured by overlapping of unfolding transition curves monitored by different probes for secondary and tertiary structure and determining changes in free energy of unfolding. Proteins stability was studied by fluorescence spectroscopy, whereas conformational changes were detected by circular dichroism techniques. We have suggested a "molten globule" like intermediate state of HSA at a fairly high concentration of GnHCl (3.2 for fatty acid free and 3.6 for fatted). The free energy of stabilization (DeltaG(D)(H2O)) in the presence of fatty acid was found to be 900 cal mol(-1). We also analyze the effects of fatty acid on binding of ligands using spectroscopic technique and reported the equilibrium constants and free energies obtained from the binding and unfolding experiments.
本研究旨在探讨脂肪酸结合对人血清白蛋白（HSA）去折叠的影响，以及脂肪酸分子如何影响和/或与结合到该蛋白质上的其他配体分子竞争。通过不同的二级和三级结构探针监测去折叠转变曲线的重叠，并测定去折叠自由能的变化，来测量结合脂肪酸的HSA和未结合脂肪酸的HSA的平衡去折叠。通过荧光光谱研究蛋白质稳定性，而通过圆二色性技术检测构象变化。我们提出在相当高浓度的盐酸胍（GnHCl）（未结合脂肪酸时为3.2，结合脂肪酸时为3.6）下，HSA存在一种类似“熔球态”的中间状态。发现存在脂肪酸时的稳定化自由能（ΔG(D)(H2O)）为900 cal mol(-1)。我们还使用光谱技术分析了脂肪酸对配体结合的影响，并报告了从结合和解折叠实验获得的平衡常数和自由能。
