Crystal structure of the A variant of human alpha1-acid glycoprotein and amitriptyline complex

Experimental Data Snapshot

  • Resolution: 2.15 Å
  • R-Value Free: 0.267 
  • R-Value Work: 0.219 
  • R-Value Observed: 0.222 

Starting Model: experimental
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Structural insights into differences in drug-binding selectivity between two forms of human alpha1-acid glycoprotein genetic variants, the A and F1*S forms.

Nishi, K.Ono, T.Nakamura, T.Fukunaga, N.Izumi, M.Watanabe, H.Suenaga, A.Maruyama, T.Yamagata, Y.Curry, S.Otagiri, M.

(2011) J Biol Chem 286: 14427-14434

  • DOI: https://doi.org/10.1074/jbc.M110.208926
  • Primary Citation of Related Structures:  
    3APU, 3APV, 3APW, 3APX

  • PubMed 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.

  • Organizational Affiliation

    Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Alpha-1-acid glycoprotein 2
A, B
190Homo sapiensMutation(s): 1 
Gene Names: AGP2ORM2
UniProt & NIH Common Fund Data Resources
Find proteins for P19652 (Homo sapiens)
Explore P19652 
Go to UniProtKB:  P19652
GTEx:  ENSG00000228278 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP19652
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.15 Å
  • R-Value Free: 0.267 
  • R-Value Work: 0.219 
  • R-Value Observed: 0.222 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 66.65α = 90
b = 45.948β = 92.14
c = 120.732γ = 90
Software Package:
Software NamePurpose
HKL-2000data reduction
SCALEPACKdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2011-02-23
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2018-11-07
    Changes: Data collection, Database references
  • Version 1.3: 2023-11-01
    Changes: Data collection, Database references, Derived calculations, Refinement description