Role of Glycine and Its Methyl-Derivatives on Conformational Stability and Dynamics of Cytochrome C

Analysis of glycine (GLY) and its methyl derivatives (N-methylglycine (MG), N, N-dimethylglycine (DMG), and glycine betaine (GB)) impacts on heat/chemical denaturation profiles of cytochrome c (H-Cyt c), molecular dynamic (MD) simulations of H-Cyt c, and CO-dissociation kinetics of natively folded carbonmonoxy-cytochrome c (MG-CO state) in aqueous or denaturant media provided important information: 1) osmolytes increase the local, global, and structural stability of H-Cyt c in the following order: GLY>MG>DMG>GB, 2) osmolytes oppose the denaturant impact to decrease the thermal stability of H-Cyt c, and it follows the order GLY>MG>DMG>GB, and 3) osmolytes decrease the structural and conformational-fluctuations of H-Cyt c. The translation of osmolyte concentration-dependent unfolding free energy to preferential hydration parameter and analysis of GLY and its methyl derivative effects on enthalpy-entropy plots and stability profiles revealed that, besides the preferential exclusion of osmolytes, the soft repulsive interactions of osmolytes with protein contribute to the osmolyte-induced enhancement in the conformational stability of H-Cyt c.