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Journal of Virology, August 2005, p. 10164-10170, Vol. 79, No. 16
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.16.10164-10170.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Identification of an Essential Molecular Contact Point on the Duck Hepatitis B Virus Reverse Transcriptase

Feng Cao,1,{dagger} Matthew P. Badtke,1,{dagger} Lisa M. Metzger,1 Ermei Yao,1 Babatunde Adeyemo,1 Yunhao Gong,1,{ddagger} and John E. Tavis1,2*

Department of Molecular Microbiology and Immunology,1 Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, Missouri2

Received 18 February 2005/ Accepted 16 May 2005

The hepadnaviral polymerase (P) functions in a complex with viral nucleic acids and cellular chaperones. To begin to identify contacts between P and its partners, we assessed the exposure of the epitopes of six monoclonal antibodies (MAbs) to the terminal protein domain of the duck hepatitis B virus P protein in a partially denaturing buffer (RIPA) and a physiological buffer (IPP150). All MAbs immunoprecipitated in vitro translated P well in RIPA, but three immunoprecipitated P poorly in IPP150. Therefore, the epitopes for these MAbs were obscured in the native conformation of P but were exposed when P was in RIPA. Epitopes for MAbs that immunoprecipitated P poorly in IPP150 were between amino acids (aa) 138 and 202. Mutation of a highly conserved motif within this region (T3; aa 176 to 183) improved the immunoprecipitation of P by these MAbs and simultaneously inhibited DNA priming by P. Peptides containing the T3 motif inhibited DNA priming in a dose-dependent manner, whereas eight irrelevant peptides did not. T3 function appears to be conserved among the hepadnaviruses because mutating T3 ablated DNA synthesis in both duck hepatitis B virus and hepatitis B virus. These results indicate that (i) the conserved T3 motif is a molecular contact point whose ligand can be competed by soluble T3 peptides, (ii) the occupancy of T3 obscures the epitopes for three MAbs, and (iii) proper occupancy of T3 by its ligand is essential for DNA priming. Therefore, small-molecule ligands that compete for binding to T3 with its natural ligand could form a novel class of antiviral drugs.

* Corresponding author. Mailing address: Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, 1402 S. Grand Blvd., St. Louis, MO 63104. Phone: (314) 977-8893. Fax: (314) 977-8717. E-mail: tavisje{at}slu.edu.

{dagger} These authors contributed equally to this work.

{ddagger} Present address: Department of Pharmacology and Therapeutics, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada.

Journal of Virology, August 2005, p. 10164-10170, Vol. 79, No. 16
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.16.10164-10170.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Stahl, M., Beck, J., Nassal, M. (2007). Chaperones Activate Hepadnavirus Reverse Transcriptase by Transiently Exposing a C-Proximal Region in the Terminal Protein Domain That Contributes to {varepsilon} RNA Binding. J. Virol. 81: 13354-13364 [Abstract] [Full Text]  
  • Stahl, M., Retzlaff, M., Nassal, M., Beck, J. (2007). Chaperone activation of the hepadnaviral reverse transcriptase for template RNA binding is established by the Hsp70 and stimulated by the Hsp90 system. Nucleic Acids Res 35: 6124-6136 [Abstract] [Full Text]  
  • Zhang, Z., Tavis, J. E. (2006). The Duck Hepatitis B Virus Reverse Transcriptase Functions as a Full-length Monomer. J. Biol. Chem. 281: 35794-35801 [Abstract] [Full Text]  


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