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Journal of Virology, November 2006, p. 11362-11369, Vol. 80, No. 22
0022-538X/06/$08.00+0     doi:10.1128/JVI.01679-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Functions of the Stem Region of the Semliki Forest Virus Fusion Protein during Virus Fusion and Assembly{triangledown}

Maofu Liao and Margaret Kielian*

Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York

Received 3 August 2006/ Accepted 31 August 2006

Membrane fusion of the alphaviruses is mediated by the E1 protein, a class II virus membrane fusion protein. During fusion, E1 dissociates from its heterodimer interaction with the E2 protein and forms a target membrane-inserted E1 homotrimer. The structure of the homotrimer is that of a trimeric hairpin in which E1 domain III and the stem region fold back toward the target membrane-inserted fusion peptide loop. The E1 stem region has a strictly conserved length and several highly conserved residues, suggesting the possibility of specific stem interactions along the trimer core and an important role in driving membrane fusion. Mutagenesis studies of the alphavirus Semliki Forest virus (SFV) here demonstrated that there was a strong requirement for the E1 stem in virus assembly and budding, probably reflecting its importance in lateral interactions of the envelope proteins. Surprisingly, however, neither the conserved length nor any specific residues of the stem were required for membrane fusion. Although the highest fusion activity was observed with wild-type E1, efficient fusion was mediated by stem mutants containing a variety of substitutions or deletions. A minimal stem length was required but could be conferred by a series of alanine residues. The lack of a specific stem sequence requirement during SFV fusion suggests that the interaction of domain III with the trimer core can provide sufficient driving force to mediate membrane merger.

* Corresponding author. Mailing address: Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461. Phone: (718) 430-3638. Fax: (718) 430-8574. E-mail: kielian{at}aecom.yu.edu.

{triangledown} Published ahead of print on 13 September 2006.

Journal of Virology, November 2006, p. 11362-11369, Vol. 80, No. 22
0022-538X/06/$08.00+0     doi:10.1128/JVI.01679-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Liu, C. Y., Kielian, M. (2009). E1 Mutants Identify a Critical Region in the Trimer Interface of the Semliki Forest Virus Fusion Protein. J. Virol. 83: 11298-11306 [Abstract] [Full Text]  
  • Qin, Z.-l., Zheng, Y., Kielian, M. (2009). Role of Conserved Histidine Residues in the Low-pH Dependence of the Semliki Forest Virus Fusion Protein. J. Virol. 83: 4670-4677 [Abstract] [Full Text]  
  • Li, Z.-N., Lee, B.-J., Langley, W. A., Bradley, K. C., Russell, R. J., Steinhauer, D. A. (2008). Length Requirements for Membrane Fusion of Influenza Virus Hemagglutinin Peptide Linkers to Transmembrane or Fusion Peptide Domains. J. Virol. 82: 6337-6348 [Abstract] [Full Text]  
  • Wu, S.-R., Haag, L., Hammar, L., Wu, B., Garoff, H., Xing, L., Murata, K., Cheng, R. H. (2007). The Dynamic Envelope of a Fusion Class II Virus: PREFUSION STAGES OF SEMLIKI FOREST VIRUS REVEALED BY ELECTRON CRYOMICROSCOPY. J. Biol. Chem. 282: 6752-6762 [Abstract] [Full Text]  


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