Structural Insights into Differences in Drug-binding Selectivity between Two Forms of Human α1-Acid Glycoprotein Genetic Variants, the A and F1*S Forms
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Human α(1)-acid glycoprotein (hAGP) in serum functions as a carrier of basic drugs. In most individuals, hAGP exists as a mixture of two genetic variants, the F1*S and A variants, which bind drugs with different selectivities. We prepared a mutant of the A variant, C149R, and showed that its drug-binding properties were indistinguishable from those of the wild type. In this study, we determined the crystal structures of this mutant hAGP alone and complexed with disopyramide (DSP), amitriptyline (AMT), and the nonspecific drug chlorpromazine (CPZ). The crystal structures revealed that the drug-binding pocket on the A variant is located within an eight-stranded β-barrel, similar to that found in the F1*S variant and other lipocalin family proteins. However, the binding region of the A variant is narrower than that of the F1*S variant. In the crystal structures of complexes with DSP and AMT, the two aromatic rings of each drug interact with Phe-49 and Phe-112 at the bottom of the binding pocket. Although the structure of CPZ is similar to those of DSP and AMT, its fused aromatic ring system, which is extended in length by the addition of a chlorine atom, appears to dictate an alternative mode of binding, which explains its nonselective binding to the F1*S and A variant hAGPs. Modeling experiments based on the co-crystal structures suggest that, in complexes of DSP, AMT, or CPZ with the F1*S variant, Phe-114 sterically hinders interactions with DSP and AMT, but not CPZ.
Date Issued
2011-04-22
Date Acceptance
2011-01-06
Citation
Journal of Biological Chemistry, 2011, 286 (16), pp.14427-14434
ISSN
1083-351X
Publisher
American Society for Biochemistry and Molecular Biology
Start Page
14427
End Page
14434
Journal / Book Title
Journal of Biological Chemistry
Volume
286
Issue
16
Copyright Statement
© 2011 The American Society for Biochemistry and Molecular Biology, Inc.
Subjects
Amitriptyline
Chlorpromazine
Computer Simulation
Crystallography, X-Ray
Disopyramide
Genetic Variation
Humans
Lipocalins
Models, Biological
Mutation
Orosomucoid
Protein Binding
Protein Conformation
Protein Structure, Tertiary
Biochemistry & Molecular Biology
06 Biological Sciences
11 Medical And Health Sciences
03 Chemical Sciences
Publication Status
Published