title: Probing the binding sites and the effect of berbamine on the structure of bovine serum albumin.
abstract: Berbamine, a naturally occurring isoquinoline alkaloid extracted from Berberis sp., is the active constituent of some Chinese herbal medicines and exhibits a variety of pharmacological activities. The effects of berbamine on the structure of bovine serum albumin (BSA) were investigated by circular dichroism, fluorescence and absorption spectroscopy under physiological conditions. Berbamine caused a static quenching of the intrinsic fluorescence of BSA, and the quenching data were analyzed by application of the Stern-Volmer equation. There was a single primary berbamine-binding site on BSA with a binding constant of 2.577x10(4)Lmol(-1) at 298K. The thermodynamic parameters, enthalpy change (DeltaH(0)) and entropy change (DeltaS(0)) for the reaction were -76.5kJmol(-1) and -173.4Jmol(-1)K(-1) according to the van't Hoff equation. The results showed that the hydrogen bond and van der Waals interaction were the predominant forces in the binding process. Competitive experiments revealed a displacement of warfarin by berbamine, indicating that the binding site was located at Drug sites I. The distance r between the donor (BSA) and the acceptor (berbamine) was obtained according to the Förster non-radiation energy transfer theory. The results of three-dimensional fluorescence spectra, UV-vis absorption difference spectra and circular dichroism of BSA in the presence of berbamine showed that the conformation of BSA was changed. The results provide a quantitative understanding of the effect of berbamine on the structure of bovine serum albumin, providing a useful guideline for further drug design.
authors.affiliation: State Key Laboratory of Virology, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Xiao-Xia
authors.initials: XX
authors.lastname: Cheng
authors.forename: Yi
authors.initials: Y
authors.lastname: Lui
authors.forename: Bo
authors.initials: B
authors.lastname: Zhou
authors.forename: Xiao-He
authors.initials: XH
authors.lastname: Xiao
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D044182:Benzylisoquinolines / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002417:Cattle; D006801:Humans; D015394:Molecular Structure; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D044182:Benzylisoquinolines; D012710:Serum Albumin, Bovine; C027870:berbamine