title: Factor defining the effects of glycine betaine on the thermodynamic stability and internal dynamics of horse cytochrome C.
abstract: A compatible osmolyte such as glycine betaine (GB) and low concentrations of a denaturant constrain the internal dynamics of natively folded carbonmonoxycytochrome c (NCO) at pH 7.0. GB and subdenaturing concentrations of guanidine hydrochloride (GdnHCl) or urea have a cumulative effect on the constrained dynamics of NCO. At higher denaturant concentrations, large-scale unfolding fluctuations dominate the dynamics and inclusion of GB opposes the structural fluctuations that cause unfolding of the protein. These deductions are made from kinetic and thermodynamic parameters measured for the CO dissociation reaction of NCO at varying concentrations of denaturant in the absence and presence of 1.0 M GB. Intermolecular docking between horse ferrocytochrome c and a denaturant or GB reveals that the denaturant-mediated constrained dynamics of the protein is due to polyfunctional interactions between the denaturant and different groups of protein while the GB-mediated restricted dynamics of the protein arises from both the direct interactions of GB with different side chains of Lys or Arg residues of the protein and indirect interactions of GB with the protein surface. Thermodynamic analysis of the thermal and GdnHCl-induced unfolding curves of ferrocytochrome c measured in the absence and presence of 1.0 M GB at pH 7.0 indicates that GB increases the thermodynamic stability of ferrocytochrome c at neutral pH. Analysis of thermal and urea-induced unfolding curves of ferricytochrome c measured at different GdnHCl concentrations in the absence and presence of 0.5-1.0 M GB at pH 7.0 and 3.8 suggests that GB counteracts the destabilizing effect of the denaturant at pH 7.0 but exhibits an additive effect on the destabilizing effect of the denaturant at pH 3.8.
authors: School of Chemistry and Biochemistry, Thapar University , Patiala 147004, India.
authors: Rishu
authors: R
authors: Jain
authors: Deepak
authors: D
authors: Sharma
authors: Sandeep
authors: S
authors: Kumar
authors: Rajesh
authors: R
authors: Kumar
mesh_terms: D000818:Animals; D001622:Betaine / Q000737:chemistry*; D002942:Circular Dichroism; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism*; D006736:Horses; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011487:Protein Conformation; D013816:Thermodynamics; D014508:Urea / Q000737:chemistry / Q000378:metabolism
chemical_list: D001622:Betaine; D014508:Urea; D045304:Cytochromes c