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Moza B, Qureshi SH, Islam A, Singh R, Anjum F, Moosavi-Movahedi AA, Ahmad F: A unique molten globule state occurs during unfolding of cytochrome c by LiClO4 near physiological pH and temperature: structural and thermodynamic characterization. Biochemistry. 2006 Apr 11;45(14):4695-702.
We have carried out denaturation studies of bovine cytochrome c (cyt c) by LiClO4 at pH 6.0 and 25 degrees C by observing changes in difference molar absorbance at 400 nm (Deltaepsilon400), mean residue ellipticities at 222 nm ([theta] 222) and difference mean residue ellipticity at 409 nm (Delta [theta] 409). The denaturation is a three-step process when measured by Deltaepsilon400 and Delta [theta] 409, and it is a two-step process when monitored by [theta] 222. The stable folding intermediate state has been characterized by near- and far-UV circular dichroism, tryptophan fluorescence, 8-anilino-1-naphthalene sulfonic acid (ANS) binding, and intrinsic viscosity measurements. A comparison of the conformational and thermodynamic properties of the LiClO4-induced molten globule (MG) state with those induced by other solvent conditions (e.g., low pH, LiCl, and CaCl2) suggests that LiClO4 induces a unique MG state, i.e., (i) the core in the LiClO4-induced state retains less secondary and tertiary structure than that in the MG states obtained in other solvent conditions, and (ii) the thermodynamic stability associated with the LiClO4-induced process, native state <--> MG state, is the same as that observed for each transition between native and MG states induced by other solvent conditions. |
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