Guanidinium chloride and urea denaturations of beta-lactoglobulin A at pH 2.0 and 25 degrees C: the equilibrium intermediate contains non-native structures (helix, tryptophan and hydrophobic patches).
We have carried out guanidinium chloride (GdmCl) and urea denaturations of bovine beta-lactoglobulin A (beta-lgA) at pH 2.0 and 25 degrees C, using far-UV and near-UV circular dichroism, near-UV absorption and tryptophan fluorescence spectroscopies. The stable intermediate state that occurs during GdmCl denaturation has been characterized by the far- and near-UV circular dichroism, tryptophan difference absorption, tryptophan fluorescence and 8-anilino-1-naphthalene sulphonic acid binding measurements. Following conclusions have been reached. (a) Urea-induced denaturation is not a two-state process. (b) GdmCl-induced denaturation is composed of two distinct two-state processes. (c) alpha-Helical content, burial of tryptophan residues and burial of hydrophobic surface area are more in the GdmCl-induced stable intermediate than those originally present in the native protein.
Dar
Tanveer Ali
TA
Department of Biosciences, Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi-110 025, India.
Singh
Laishram Rajendrakumar
LR
Islam
Asimul
A
Anjum
Farah
F
Moosavi-Movahedi
Ali Akbar
AA
Ahmad
Faizan
F
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D019791:Guanidine / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry* / Q000378:metabolism; D010277:Parasympathomimetics / Q000494:pharmacology*; D011489:Protein Denaturation / Q000187:drug effects*; D017433:Protein Structure, Secondary; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000737:chemistry*; D014508:Urea / Q000494:pharmacology*
D007782:Lactoglobulins; D010277:Parasympathomimetics; D014364:Tryptophan; D014508:Urea; D019791:Guanidine