title: A site-directed mutagenesis study of drug-binding selectivity in genetic variants of human alpha(1)-acid glycoprotein.
abstract: Human alpha(1)-acid glycoprotein (AGP), a major carrier of many basic drugs in circulation, consists of at least two genetic variants, namely A and F1*S variant. Interestingly, the variants of AGP have different drug-binding properties. The purpose of this study was to identify the amino acid residues that are responsible for the selectivity of drug binding to genetic variants of AGP using site-directed mutagenesis. First, we screened amino acid residues in the region proximal to position 100 that are involved in binding of warfarin and dipyridamole, which are F1*S-specific ligands, and of propafenone, which is an A-specific ligand, using ultrafiltration. In the F1*S variant, His97, His100, and Trp122 were involved in either warfarin- or dipyridamole-binding, while Glu92, His100, and Trp122 participated in the binding of propafenone in the A variant. Exchange of the residue at position 92 between AGP variants reversed the relative strength of propafenone binding to the two variants, but had a markedly different effect on binding of warfarin and dipyridamole. These findings indicate that the amino acid residue at position 92 plays a significant role in drug-binding selectivity in AGP variants, especially for drugs that preferentially bind to the A variant.
authors.affiliation: Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Nishi
authors.forename: Megumi
authors.initials: M
authors.lastname: Ueno
authors.forename: Yuka
authors.initials: Y
authors.lastname: Murakami
authors.forename: Naoko
authors.initials: N
authors.lastname: Fukunaga
authors.forename: Teruo
authors.initials: T
authors.lastname: Akuta
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kadowaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Ayaka
authors.initials: A
authors.lastname: Suenaga
authors.forename: Toru
authors.initials: T
authors.lastname: Maruyama
authors.forename: Masaki
authors.initials: M
authors.lastname: Otagiri
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009961:Orosomucoid / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D008024:Ligands; D009961:Orosomucoid; D011994:Recombinant Proteins