GM1-Induced Structural Changes of Bovine Serum Albumin after Chemical and Thermal Disruption of the Secondary Structure;A Spectroscopic Comparison

摘要

GM1-induced structural transitions of native and unfolded conformers of bovine serum albumin (BSA) have been studied where in the unfolded conformers,the secondary structures were disrupted either chemically by 8 M urea or thermally by heating at 65 °C.With decreasing protein:ganglioside ratio at pH 7.0,the native BSA partially unfolds and expands,while the urea-denatured BSA forms an a-helical structural pattern with shrinking in the conformational space.However,a continuous loss of a-helicity with minor increase in size was observed for the thermally altered protein in the presence of the GM1 micelle.The changes in the secondary structural content were followed by far-UV circular dichroism (CD) analysis.The dynamic light scattering (DLS) experiments were used to study the variation of the size of the protein-GM1 complexes with increasing concentration of the GM1.Fluorescence experiments,show that tryptophan residues of BSA experience a more hydrophobic environment in the presence of the GM1 micelle wim a decreasing protein:ganglioside ratio at pH 7.0.The present study shows that GM1 has a strong effect on the conformation of BSA depending on the conformational states of the protein that would relate to a physiological function of GM1 such as acting as the receptor of proteins in the cell membrane.