pH- and heat-induced structural changes of bovine alpha -lactalbumin in response to oleic acid binding.

摘要

Bovine alpha -lactalbumin ( alpha -LA) is able to interact with fatty acids, resulting in structural changes that are potentially responsible for the HAMLET/BAMLET role. Different states of alpha -LA induced by pH, temperature and fatty acid binding have been examined. Evidences of the structural changes of alpha -LA in molten globule and native states in correlation with oleic acid (OA) binding are shown using fluorescence spectroscopy and in silico approach. In addition, the alpha -LA was subjected to automated docking analysis, to better understand the interaction with oleic acid, using the PatchDock algorithm. The experimental results demonstrate a more flexible conformation of the protein at pH 2.5 when compared to neutral pH, thus facilitating the oleic acid binding to alpha -LA. The quenching experiments indicate the remarkable increase in the content of molten globule state at pH 2.5 and a more compact and rigid structure for alpha -LA-OA complexes at pH 7.0. The docking results are consistent with the experimental data concerning the thermal stability of the alpha -LA-OA complex. alpha -LA in different conformations/complexes was sensitive to pH and temperature. Several different molecular species induced by pH, heat treatment and oleic acid binding were suggested. The structure of the protein was more flexible at acidic pH, therefore favoring the hydrophobic exposure.