A site-directed mutagenesis study of drug-binding selectivity in genetic variants of human α1-acid glycoprotein

✍ Scribed by Koji Nishi; Megumi Ueno; Yuka Murakami; Naoko Fukunaga; Teruo Akuta; Daisuke Kadowaki; Hiroshi Watanabe; Ayaka Suenaga; Toru Maruyama; Masaki Otagiri

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 205 KB
• Volume: 98
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.21697

✦ Synopsis

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.