E1 mutants identify a critical region in the trimer interface of the Semliki Forest virus fusion protein

Catherine Y. Liu, Margaret Kielian

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The alphavirus Semliki Forest virus (SFV) uses a membrane fusion reaction to infect host cells. Fusion of the virus and cell membranes is triggered by low pH in the endosome and is mediated by the viral membrane protein E1. During fusion, E1 inserts into the target membrane, trimerizes, and refolds into a hairpin conformation. Formation of the E1 homotrimer is critical to membrane fusion, but the mechanism of trimerization is not understood. The crystal structure of the postfusion E1 trimer shows that an aspartate residue, D188, is positioned in the central core trimer interface. D188 is conserved in all reported alphavirus E1 sequences. We tested the contribution of this amino acid to trimerization and fusion by replacing D188 with alanine (D188A) or lysine (D188K) in an SFV infectious clone. These mutations were predicted to disrupt specific interactions at this position and/or change their pH dependence. Our results indicated that the D188K mutation blocked SFV fusion and infection. At low pH, D188K E1 inserted into target membranes but was trapped as a target membrane-inserted monomer that did not efficiently form the stable core trimer. In contrast, the D188A mutant was infectious, although trimerization and fusion required a lower pH. While there are extensive contacts between E1 subunits in the homotrimer, the D188K mutant identifies an important "hot spot" for protein-protein interactions within the core trimer.

Original languageEnglish (US)
Pages (from-to)11298-11306
Number of pages9
JournalJournal of Virology
Volume83
Issue number21
DOIs
StatePublished - Nov 2009

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viral fusion proteins
Semliki Forest virus
Viral Fusion Proteins
Semliki forest virus
Alphavirus
mutants
Membrane Fusion
Alanine
alanine
Membranes
Viral Matrix Proteins
mutation
Mutation
endosomes
Endosomes
viral proteins
protein-protein interactions
Virus Diseases
aspartic acid
crystal structure

ASJC Scopus subject areas

  • Immunology
  • Virology

Cite this

E1 mutants identify a critical region in the trimer interface of the Semliki Forest virus fusion protein. / Liu, Catherine Y.; Kielian, Margaret.

In: Journal of Virology, Vol. 83, No. 21, 11.2009, p. 11298-11306.

Research output: Contribution to journalArticle

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