Crystal structure of human hypoxanthine-guanine phosphoribosyltransferase in complex with 6-fluoro-3-hydroxy-2-pyrazinecarboxamide (T-705) ribose-5'-monophosphate

Experimental Data Snapshot

  • Resolution: 2.73 Å
  • R-Value Free: 0.278 
  • R-Value Work: 0.248 
  • R-Value Observed: 0.251 

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Role of human hypoxanthine Guanine phosphoribosyltransferase in activation of the antiviral agent T-705 (favipiravir).

Naesens, L.Guddat, L.W.Keough, D.T.van Kuilenburg, A.B.Meijer, J.Vande Voorde, J.Balzarini, J.

(2013) Mol Pharmacol 84: 615-629

  • DOI: https://doi.org/10.1124/mol.113.087247
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    6-Fluoro-3-hydroxy-2-pyrazinecarboxamide (T-705) is a novel antiviral compound with broad activity against influenza virus and diverse RNA viruses. Its active metabolite, T-705-ribose-5'-triphosphate (T-705-RTP), is recognized by influenza virus RNA polymerase as a substrate competing with GTP, giving inhibition of viral RNA synthesis and lethal virus mutagenesis. Which enzymes perform the activation of T-705 is unknown. We here demonstrate that human hypoxanthine guanine phosphoribosyltransferase (HGPRT) converts T-705 into its ribose-5'-monophosphate (RMP) prior to formation of T-705-RTP. The anti-influenza virus activity of T-705 and T-1105 (3-hydroxy-2-pyrazinecarboxamide; the analog lacking the 6-fluoro atom) was lost in HGPRT-deficient Madin-Darby canine kidney cells. This HGPRT dependency was confirmed in human embryonic kidney 293T cells undergoing HGPRT-specific gene knockdown followed by influenza virus ribonucleoprotein reconstitution. Knockdown for adenine phosphoribosyltransferase (APRT) or nicotinamide phosphoribosyltransferase did not change the antiviral activity of T-705 and T-1105. Enzymatic assays showed that T-705 and T-1105 are poor substrates for human HGPRT having Km(app) values of 6.4 and 4.1 mM, respectively. Formation of the RMP metabolites by APRT was negligible, and so was the formation of the ribosylated metabolites by human purine nucleoside phosphorylase. Phosphoribosylation and antiviral activity of the 2-pyrazinecarboxamide derivatives was shown to require the presence of the 3-hydroxyl but not the 6-fluoro substituent. The crystal structure of T-705-RMP in complex with human HGPRT showed how this compound binds in the active site. Since conversion of T-705 by HGPRT appears to be inefficient, T-705-RMP prodrugs may be designed to increase the antiviral potency of this new antiviral agent.

  • Organizational Affiliation

    Rega Institute for Medical Research, KU Leuven, Leuven, Belgium (L.N., J.V.V., J.B.); School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland, Australia (L.W.G., D.T.K.); and Laboratory of Genetic Metabolic Diseases, Academic Medical Center, Amsterdam, The Netherlands (A.B.P.v.K., J.M.).

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Hypoxanthine-guanine phosphoribosyltransferase216Homo sapiensMutation(s): 0 
Gene Names: HPRT1HPRT
UniProt & NIH Common Fund Data Resources
Find proteins for P00492 (Homo sapiens)
Explore P00492 
Go to UniProtKB:  P00492
PHAROS:  P00492
GTEx:  ENSG00000165704 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP00492
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on 1RP

Download Ideal Coordinates CCD File 
B [auth A]6-fluoro-3-oxo-4-(5-O-phosphono-beta-D-ribofuranosyl)-3,4-dihydropyrazine-2-carboxamide
C10 H13 F N3 O9 P
Experimental Data & Validation

Experimental Data

  • Resolution: 2.73 Å
  • R-Value Free: 0.278 
  • R-Value Work: 0.248 
  • R-Value Observed: 0.251 
  • Space Group: I 2 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 46.858α = 90
b = 73.4β = 90
c = 109.134γ = 90
Software Package:
Software NamePurpose
ADSCdata collection
XDSdata reduction
SCALAdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2013-08-14
    Type: Initial release
  • Version 1.1: 2013-09-25
    Changes: Database references