title: Characterization of a dimeric unfolding intermediate of bovine serum albumin under mildly acidic condition.
abstract: Protein aggregation is a well-known phenomenon related to serious medical implications. Bovine serum albumin (BSA), a structural analogue of human serum albumin, has a natural tendency for aggregation under stress conditions. While following effect of moderately acidic pH on BSA, a state was identified at pH 4.2 having increased light scattering capability at 350 nm. It was essentially a dimer devoid of disulphide linked large aggregates as observed from 'spin column' experiments, gel electrophoresis and ultra-centrifugations. Its surface hydrophobic character was comparable to the native conformer at pH 7.0 as observed by the extraneous fluorescence probes pyrene and pyrene maleimide but its interactions with 1-anilino 8-naphthelene sulphonic acid was more favorable. Dimerization was irreversible between pH 4.2 and 7.0 even after treatment with DTT. The role of the only cysteine-34 residue was investigated where modification with reagents of arm length bigger than 6 A prevented dimerization. Molecular modeling of BSA indicated that cys-34 resides in a cleft of 6 A depth. This indicated that the area surrounding the cleft plays important role in inducing the dimerization.
authors.affiliation: Division of Drug Design, Development and Molecular Modeling, Indian Institute of Chemical Biology, 4, Raja S.C. Mallick Road, Jadavpur, Calcutta-700032, India.
authors.forename: Amrita
authors.initials: A
authors.lastname: Brahma
authors.forename: Chhabinath
authors.initials: C
authors.lastname: Mandal
authors.forename: Debasish
authors.initials: D
authors.lastname: Bhattacharyya
mesh_terms: D000818:Animals; D002417:Cattle; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008027:Light; D008623:Mercaptoethanol / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D008970:Molecular Weight; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D012542:Scattering, Radiation; D012709:Serum Albumin / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013439:Sulfhydryl Reagents / Q000737:chemistry; D013696:Temperature
chemical_list: D012709:Serum Albumin; D013439:Sulfhydryl Reagents; D012710:Serum Albumin, Bovine; D008623:Mercaptoethanol; D003545:Cysteine