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 Google Scholar
Google Scholar
Right arrow Articles by Parrott, M. M.
Right arrow Articles by Mukhopadhyay, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Parrott, M. M.
Right arrow Articles by Mukhopadhyay, S.

 Previous Article  |  Next Article 

Journal of Virology, March 2009, p. 2584-2591, Vol. 83, No. 6
0022-538X/09/$08.00+0     doi:10.1128/JVI.02158-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Role of Conserved Cysteines in the Alphavirus E3 Protein {triangledown}

Megan M. Parrott,1 Sarah A. Sitarski,1,{dagger} Randy J. Arnold,2 Lora K. Picton,3 R. Blake Hill,3 and Suchetana Mukhopadhyay1*

Department of Biology,1 Department of Chemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, Indiana 47405,2 Department of Biology, The Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 212183

Received 13 October 2008/ Accepted 18 December 2008

Alphavirus particles are covered by 80 glycoprotein spikes that are essential for viral entry. Spikes consist of the E2 receptor binding protein and the E1 fusion protein. Spike assembly occurs in the endoplasmic reticulum, where E1 associates with pE2, a precursor containing E3 and E2 proteins. E3 is a small, cysteine-rich, extracellular glycoprotein that mediates proper folding of pE2 and its subsequent association with E1. In addition, cleavage of E3 from the assembled spike is required to make the virus particles efficiently fusion competent. We have found that the E3 protein in Sindbis virus contains one disulfide bond between residues Cys19 and Cys25. Replacing either of these two critical cysteines resulted in mutants with attenuated titers. Replacing both cysteines with either alanine or serine resulted in double mutants that were lethal. Insertion of additional cysteines based on E3 proteins from other alphaviruses resulted in either sequential or nested disulfide bond patterns. E3 sequences that formed sequential disulfides yielded virus with near-wild-type titers, while those that contained nested disulfide bonds had attenuated activity. Our data indicate that the role of the cysteine residues in E3 is not primarily structural. We hypothesize that E3 has an enzymatic or functional role in virus assembly, and these possibilities are further discussed.

* Corresponding author. Mailing address: Department of Biology, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN 47405. Phone: (812) 856-3686. Fax: (812) 856-5710. E-mail: sumukhop{at}indiana.edu

{triangledown} Published ahead of print on 24 December 2008.

{dagger} Present address: Wells Center for Pediatric Research, 1044 W. Walnut St., R4-431B, Indianapolis, IN 46202.

Journal of Virology, March 2009, p. 2584-2591, Vol. 83, No. 6
0022-538X/09/$08.00+0     doi:10.1128/JVI.02158-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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