Salt-induced refolding in different domains of partially folded bovine serum albumin.
In our earlier communication on urea denaturation of bovine serum albumin (BSA), we showed significant unfolding of domain III along with domain I prior to intermediate formation around 4.6-5.2 M urea based on the binding results of domain specific ligands:chloroform, bilirubin and diazepam for domains I, II and III, respectively. Here, we present our results on the salt-induced refolding of the two partially folded states of BSA obtained at 4.5 M urea and at pH 3.5, respectively. Both these states were characterized by significant unfolding of both domains I and III as indicated by decreased binding of chloroform and diazepam, respectively. Salt-induced stabilization of partially folded states of BSA was accompanied by nearly complete refolding of both domains I and III as the binding isotherms of chloroform and diazepam obtained in presence of approximately 1.0 M KCl were nearly identical to that obtained with native BSA at pH 7.4. From these observations, it can be concluded that the anion binding sites on serum albumin are not only confined to domain III (C-terminal region) but few sites are also present on domain I (or N-terminal region) of the protein.
Tayyab
Saad
S
Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202 002, India. btisamua@nde.vsnl.net.in
Ahmad
Basir
B
Kumar
Yogesh
Y
Khan
Mohd Mushahid
MM
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002725:Chloroform / Q000378:metabolism; D002942:Circular Dichroism; D003975:Diazepam / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D011189:Potassium Chloride; D017510:Protein Folding; D020673:Protein Renaturation; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D012710:Serum Albumin, Bovine; D011189:Potassium Chloride; D002725:Chloroform; D003975:Diazepam