Pressure- and urea-induced denaturation of bovine serum albumin: considerations about protein heterogeneity

• Grant number: 12/00121-0
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: March 01, 2012
• End date: August 31, 2012
• Field of knowledge: Biological Sciences - Biophysics - Biophysics of Processes and Systems
• Principal Investigator: Carlos Francisco Sampaio Bonafe
• Grantee: Carlos Francisco Sampaio Bonafe
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Urea denatures proteins at different concentrations, depending on the experimental conditions and the protein. We investigated the pressure-induced denaturation of bovine serum albumin (BSA) in the presence of subdenaturing concentrations of urea based on a two-state equilibrium. Pressure-induced denaturation was enhanced at urea concentrations ([U]) of 3.5 M to 8.0 M, with the free energy of denaturation at atmospheric pressure ranging from +5.0 to -2.5 kJ/mol of BSA. The m values appeared to be biphasic, with m1 and m2 of 0.92 and 2.35 kJ mol-1 M-1, respectively. Plots of free energy of denaturation versus ln[U] yielded values of u, the apparent stoichiometric coefficient, of 1.68 and 6.67 mol of urea/mol of BSA for m1 and m2, respectively. These values were compared with the m and u values of other monomeric proteins reported in or calculated from the literature. The very low values of u systematically observed for proteins were suggestive of heterogeneity in the free energy of denaturation. Thus, a u value of 140 mol of urea/mol of BSA may indicate the existence of a heterogeneous molecular population with respect to the free energy of denaturation. (AU)