This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Delos, S. E.
Right arrow Articles by White, J. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Delos, S. E.
Right arrow Articles by White, J. M.

 Previous Article  |  Next Article 

Journal of Virology, March 2005, p. 3488-3499, Vol. 79, No. 6
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.6.3488-3499.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Receptor-Induced Conformational Changes in the SU Subunit of the Avian Sarcoma/Leukosis Virus A Envelope Protein: Implications for Fusion Activation

Sue E. Delos,* Jesse A. Godby, and Judith M. White

Department of Cell Biology, University of Virginia, Charlottesville, Virginia

Received 26 August 2004/ Accepted 10 November 2004

The avian sarcoma/leukosis virus (ASLV) is activated for fusion by a two-step mechanism. For ASLV subgroup A (ASLV-A), association with its receptor (Tva) at neutral pH converts virions to a form that can bind target membranes and, in some assays, induce the lipid-mixing stage of fusion. Low pH is necessary to complete the fusion reaction. ASLV-A env (EnvA) exists on the viral surface as a trimer of heterodimers consisting of receptor binding (SU-A) and fusion-mediating (TM-A) subunits. As the receptor binding and fusion-mediating functions reside in separate subunits, we hypothesize that SU-A and TM-A are conformationally coupled. To begin to understand the effect of the binding of a soluble 47-residue domain of the receptor (sTva) on this coupling and the subsequent function of low pH, we prepared recombinant proteins representing full-length SU-A and a nested set of deletion mutant proteins. Full-length SU-A binds sTva with high affinity, but even small deletions at either the N or the C terminus severely impair sTva binding. We have purified the full-length SU-A subunit and characterized its interactions with sTva and the subsequent effect of low pH on the complex. sTva binds SU-A with an apparent KD of 3 pM. Complex formation occludes hydrophobic surfaces and tryptophan residues and leads to a partial loss of {alpha}-helical structure in SU-A. Low pH does not alter the off rate for the complex, further alter the secondary structure of SU-A, or induce measurable changes in tryptophan environment. The implications of these findings for fusion are discussed.

* Corresponding author. Mailing address: Department of Cell Biology, UVA Health System, School of Medicine, P.O. Box 800732, Charlottesville, VA 22908-0732. Phone: (434) 924-2009. Fax: (434) 982-3912. E-mail: sed7a{at}virginia.edu.

Journal of Virology, March 2005, p. 3488-3499, Vol. 79, No. 6
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.6.3488-3499.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Kolokoltsov, A. A., Deniger, D., Fleming, E. H., Roberts, N. J. Jr., Karpilow, J. M., Davey, R. A. (2007). Small Interfering RNA Profiling Reveals Key Role of Clathrin-Mediated Endocytosis and Early Endosome Formation for Infection by Respiratory Syncytial Virus. J. Virol. 81: 7786-7800 [Abstract] [Full Text]  
  • Contreras-Alcantara, S., Godby, J. A., Delos, S. E. (2006). The Single Ligand-binding Repeat of Tva, a Low Density Lipoprotein Receptor-related Protein, Contains Two Ligand-binding Surfaces. J. Biol. Chem. 281: 22827-22838 [Abstract] [Full Text]  


Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»