title: Role of macromolecular crowding and salt ions on the structural-fluctuation of a highly compact configuration of carbonmonoxycytochrome c.
abstract: Carbonmonoxycytochrome c refolds to a native-like compact state (NCO-state), where the non-native Fe(2+)-CO interaction persists. Structural and molecular properties extracted from CD, fluorescence and NMR experiments reveal that the NCO-state shows the generic properties of molten globules. Slow thermal-dissociation of CO transforms the NCO-state to native-state (N-state), where the native Fe(2+)-M80 bond recovers. To determine the role of crowding agents and salt ions on the structural-fluctuation of NCO, the kinetic and thermodynamic parameters for CO-dissociation from NCO (NCO→N+CO) were measured at varying concentrations of crowding agents (dextran 70, dextran 40, ficoll 70) and salt ions (anion: ClO4(-), I(-), Br(-), NO3(-), Cl(-); cation: NH4(+), K(+), Na(+)). As [crowding agent] or [ion] is increased, the rate coefficient of CO-dissociation (kdiss) decreases exponentially. Furthermore, the extent of decrease in kdiss is found to be dependent on (i) size, charge density and charge dispersion of the ion, and (ii) size, shape, and viscosity of the crowding agent.
authors.affiliation: School of Chemistry and Biochemistry, Thapar University, Patiala 147004, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Council of Scientific and Industrial Research, Institute of Microbial Technology, Sector 39A, Chandigarh, India.
authors.forename: Deepak
authors.initials: D
authors.lastname: Sharma
authors.affiliation: School of Chemistry and Biochemistry, Thapar University, Patiala 147004, India.
authors.forename: Rishu
authors.initials: R
authors.lastname: Jain
authors.affiliation: School of Chemistry and Biochemistry, Thapar University, Patiala 147004, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Kumar
authors.affiliation: School of Chemistry and Biochemistry, Thapar University, Patiala 147004, India. Electronic address: rajesh.kumar@thapar.edu.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
mesh_terms: D000818:Animals; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D009206:Myocardium / Q000201:enzymology; D017434:Protein Structure, Tertiary; D012492:Salts / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D007477:Ions; D012492:Salts; D045304:Cytochromes c
keywords: Enthalpic and entropic effects; Excluded volume effect; Macromolecular crowding effect; Molten globule; Structural-fluctuation; Van der Waals bumps