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.
Department of Biosciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110 025, India.
Beenu
B
Moza
Shabir Hussain
SH
Qureshi
Asimul
A
Islam
Rajendrakumar
R
Singh
Farah
F
Anjum
Ali Akbar
AA
Moosavi-Movahedi
Faizan
F
Ahmad
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