Chlorogenic Acid Enhances the Chaperone Potential of BSA at Physiological Concentrations on Model Protein Cytochrome c.

ABSTRACT

Neurodegenerative disorders are associated with the accumulation of disease-related proteins intracellularly and extracellularly. Extracellular chaperones play a crucial role in clearing the extracellularly accumulated proteins. In this study, we observed the extracellular chaperone-like potential of BSA at physiological concentrations on model protein cytochrome c (cyt c). Kinetics of heat-induced aggregation of cyt c suggest the nucleation independent first order aggregation kinetics. Aggregation of cyt c was studied in the presence of varying concentrations of BSA to assess its chaperone nature. At lower concentrations of BSA when the sub molar ratio of cyt cBSA are 10.6 and 11.2, heat-induced unfolded cyt c promotes the aggregation of BSA. However, as the ratio of cyt cBSA increases to 11.8, the aggregation of cyt c is reduced. When the concentration of BSA reaches physiological levels, yielding a cyt cBSA ratio of 12.4, the rate of aggregation drastically decreases reflecting its chaperone potential. These observations indicate that under physiological conditions, macromolecular crowding stabilizes the native structure of both proteins and enhances their interaction that results in the reduced aggregation of cyt c. Additionally, the presence of the phytochemical chlorogenic acid at a sub-molar ratio of 11 stabilizes cyt c and prevents its unfolding and facilitates the binding of cyt c to BSA at physiological concentrations. This interaction further decreases the overall aggregation of cyt c and stabilizes its native fold.