Changes of albumin secondary structure after palmitic acid binding. FT-IR spectroscopic study.

Abstract

Albumin is an universal transport protein. Plasma pool of free fatty acids arising from triglyceride hydrolysis, critical in energy metabolism and etiology of metabolic disorders is transported by albumin. According to various studies albumin has from seven to nine binding sites with diverse affinity to long chain fatty acids. X-ray diffraction crystallography measurements have provided data only for pure human serum albumin or albumin with fully saturated binding sites. These results have shown that amount of -helices is higher after fatty acids binding. Molecular mechanics simulations suggest that binding of fatty acids in two high-affinity sites leads to major conformational changes in albumin structure. The aim of this research was to investigate albumin secondary structure upon gradually increasing fatty acids to protein mole ratio. Fourier transform infrared spectroscopy was applied to study changes of bovine serum albumin (as an analogue of human serum albumin) -helical structures after binding palmitic acid in a range of 0-20 palmitic acid: albumin molar ratios representing pure protein, partial, full saturation and excess binding sites capacity. Amount of -helices was increasing along with the amount of palmitic acid: bovine serum albumin molar ratio and reached maximum value around 2 mol/mol. Our studies confirmed molecular mechanics simulations and crystallographic studies. Palmitic acid binding in two high-affinity sites leads to major structural changes, filling another sites only slightly influenced bovine serum albumin secondary structure. The systematic study of fatty acids and albumin interactions, using an experimental model mimicking metabolic disorders, may results in new tools for personalized nanopharmacotherapy.