The effects of urea on protein stability: The role in the dehydration of the counterions

C. GASTÓN FERRARA; RICARDO YANIS ESPINOSA

Ciudad Autonoma de Buenos Aires

Conferencia; STATPHYS 2019; 2019

UBA-ICTP-EPS

The mechanism of the denaturing effects of urea on proteins is still an unsolved and important problem in protein chemistry. Mainly two opposing mechanisms are controversially discussed, according to which either hydrophobic, or polar interactions are the dominant driving force. To resolve this question, changes in the hydrogen bond network of water in the first hydration shell urea-protein, the partial dehydration of the charged amioacids and bound counterions at the protein surface were analyzed using Molecular Dynamics (MD) simulations. We studied the conformational changes in BSA at pH 7.0 and 3.7 e.i., from N-isoform to F-isoform. The system under study were a mixture of BSA (PDB code 4F5S ), urea and chlorine counterions in water. MD simulations were performed using the GROMACS 2016-3 package. The Gromos 54A7 force field was employed to account for intermolecular interactions and, PDB2PQR algorithm was used to estimate the state of ionization of titratable residues in Bovine Serum Albumin (BSA) at pH 7.0 and 3.7. The results obtained show clearly influence of the urea over protein structure. Thus, the urea electrostatically interact with chlorine counterions in water produced a weakening in the interaction between Cl ion and the BSA, dehydrating of both the charged head and bound counterions at the protein surface.