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

 Previous Article  |  Next Article 

Journal of Virology, May 2003, p. 5389-5400, Vol. 77, No. 9
0022-538X/03/$08.00+0     DOI: 10.1128/JVI.77.9.5389-5400.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Disulfide Bonding among µ1 Trimers in Mammalian Reovirus Outer Capsid: a Late and Reversible Step in Virion Morphogenesis

Departments of Microbiology and Molecular Genetics,¹ Biological Chemistry and Molecular Pharmacology, Harvard Medical School,⁴ Laboratory of Molecular Medicine and Howard Hughes Medical Institute, Children's Hospital, Boston, Massachusetts 02115,³ Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706²

Received 15 October 2002/ Accepted 5 February 2003

We examined how a particular type of intermolecular disulfide (ds) bond is formed in the capsid of a cytoplasmically replicating nonenveloped animal virus despite the normally reducing environment inside cells. The µ1 protein, a major component of the mammalian reovirus outer capsid, has been implicated in penetration of the cellular membrane barrier during cell entry. A recent crystal structure determination supports past evidence that the basal oligomer of µ1 is a trimer and that 200 of these trimers surround the core in the fenestrated T=13 outer capsid of virions. We found in this study that the predominant forms of µ1 seen in gels after the nonreducing disruption of virions are ds-linked dimers. Cys679, near the carboxyl terminus of µ1, was shown to form this ds bond with the Cys679 residue from another µ1 subunit. The crystal structure in combination with a cryomicroscopy-derived electron density map of virions indicates that the two subunits that contribute a Cys679 residue to each ds bond must be from adjacent µ1 trimers in the outer capsid, explaining the trimer-dimer paradox. Successful in vitro assembly of the outer capsid by a nonbonding mutant of µ1 (Cys679 substituted by serine) confirmed the role of Cys679 and suggested that the ds bonds are not required for assembly. A correlation between µ1-associated ds bond formation and cell death in experiments in which virions were purified from cells at different times postinfection indicated that the ds bonds form late in infection, after virions are exposed to more oxidizing conditions than those in healthy cells. The infectivity measurements of the virions with differing levels of ds-bonded µ1 showed that these bonds are not required for infection in culture. The ds bonds in purified virions were susceptible to reduction and reformation in situ, consistent with their initial formation late in morphogenesis and suggesting that they may undergo reduction during the entry of reovirus particles into new cells.

This article has been cited by other articles:

• Trask, S. D., Dormitzer, P. R. (2006). Assembly of Highly Infectious Rotavirus Particles Recoated with Recombinant Outer Capsid Proteins. J. Virol. 80: 11293-11304 [Abstract] [Full Text]  
• Huang, I-C., Bosch, B. J., Li, F., Li, W., Lee, K. H., Ghiran, S., Vasilieva, N., Dermody, T. S., Harrison, S. C., Dormitzer, P. R., Farzan, M., Rottier, P. J. M., Choe, H. (2006). SARS Coronavirus, but Not Human Coronavirus NL63, Utilizes Cathepsin L to Infect ACE2-expressing Cells. J. Biol. Chem. 281: 3198-3203 [Abstract] [Full Text]  
• Odegard, A. L., Chandran, K., Zhang, X., Parker, J. S. L., Baker, T. S., Nibert, M. L. (2004). Putative Autocleavage of Outer Capsid Protein {micro}1, Allowing Release of Myristoylated Peptide {micro}1N during Particle Uncoating, Is Critical for Cell Entry by Reovirus. J. Virol. 78: 8732-8745 [Abstract] [Full Text]