A unique molten globule state occurs during unfolding of cytochrome c by LiClO4 near physiological pH and temperature: structural and thermodynamic characterization.
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.
Moza
Beenu
B
Department of Biosciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110 025, India.
Qureshi
Shabir Hussain
SH
Islam
Asimul
A
Singh
Rajendrakumar
R
Anjum
Farah
F
Moosavi-Movahedi
Ali Akbar
AA
Ahmad
Faizan
F
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D045304:Cytochromes c / Q000737:chemistry*; D018020:Lithium Compounds / Q000494:pharmacology*; D010472:Perchlorates / Q000494:pharmacology*; D011487:Protein Conformation / Q000187:drug effects*; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects; D013053:Spectrophotometry; D013816:Thermodynamics
D018020:Lithium Compounds; D010472:Perchlorates; D045304:Cytochromes c; C054684:lithium perchlorate