title: A molten globule-like intermediate state detected in the thermal transition of cytochrome c under low salt concentration.
abstract: To understand the stabilization mechanism of the transient intermediate state in protein folding, it is very important to understand the structure and stability of the molten globule state under a native condition, in which the native state exists stably. The thermal transitions of horse cytochrome c were thermodynamically evaluated by highly precise differential scanning calorimetry (DSC) at pH 3.8-5.0. The heat capacity functions were analyzed using double deconvolution and the nonlinear least-squares method. An intermediate (I) state is clearly confirmed in the thermal native (N)-to-denatured (D) transition of horse cytochrome c. The mole fraction of the intermediate state shows the largest value, 0.4, at nearly 70 degrees C at pH 4.1. This intermediate state was also detected by the circular dichroism (CD) method and was found to have the properties of the molten globule-like structure by three-state analysis of the CD data. The Gibbs free-energy change between N and I, DeltaG(NI), and that between N and D, DeltaG(ND), were evaluated to be 9-22 kJ mol(-1) and 41-45 kJ mol(-1), respectively at 15( ) degrees C and pH 4.1.
authors.affiliation: Department of Bioengineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188, Japan.
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Nakamura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Baba
authors.forename: Shun-Ichi
authors.initials: S
authors.lastname: Kidokoro
mesh_terms: D000818:Animals; D002151:Calorimetry; D002942:Circular Dichroism; D045304:Cytochromes c / Q000737:chemistry*; D004795:Enzyme Stability; D017510:Protein Folding; D012492:Salts / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry*; D013816:Thermodynamics; D044366:Transition Temperature
chemical_list: D012492:Salts; D012965:Sodium Chloride; D045304:Cytochromes c