fus-1, a pH shift mutant of Semliki Forest virus, acts by altering spike subunit interactions via a mutation in the E2 subunit

Sallie Glomb-Reinmund, Margaret Kielian

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Abstract

Semliki Forest virus (SFV), an enveloped alphavirus, is a well- characterized paradigm for viruses that infect cells via endocytic uptake and low-pH-triggered fusion. The SFV spike protein is composed of a dimer of E1 and E2 transmembrane subunits, which dissociate upon exposure to low pH, liberating E2 and the fusogenic E1 subunit to undergo independent conformational changes. SFV fusion and infection are blocked by agents such as ammonium chloride, which act by raising the pH in the endosome and inhibiting the low-pH-induced conformational changes in the SFV spike protein. We have previously isolated an SFV mutant, fus-1, that requires more acidic pH to trigger its fusion activity and is therefore more sensitive to inhibition by ammonium chloride. The acid shift in the fusion activity of fus-1 was here shown to be due to a more acidic pH threshold for the initial dissociation of the fus-1 spike dimer, thereby resulting in a more acidic pH requirement for the subsequent conformational changes in both fus-1 E1 and fus-1 E2. Sequence analysis demonstrated that the fus-1 phenotype was due to a mutation in the E2 spike subunit, threonine 12 to isoleucine. fus-1 revertants that have regained the parental fusion phenotype and ammonium chloride sensitivity were shown to have also regained E2 threonine 12. Our results identify a region of the SFV E2 spike protein subunit that regulates the pH dependence of E1-catalyzed fusion by controlling the dissociation of the E1/E2 dimer.

Original languageEnglish (US)
Pages (from-to)4281-4287
Number of pages7
JournalJournal of Virology
Volume72
Issue number5
StatePublished - May 1998

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Semliki Forest virus
Semliki forest virus
mutation
mutants
Mutation
Ammonium Chloride
ammonium chloride
Threonine
threonine
Alphavirus
Phenotype
phenotype
endosomes
Isoleucine
Endosomes
Protein Subunits
Virus Diseases
protein subunits
isoleucine
Sequence Analysis

ASJC Scopus subject areas

  • Immunology

Cite this

fus-1, a pH shift mutant of Semliki Forest virus, acts by altering spike subunit interactions via a mutation in the E2 subunit. / Glomb-Reinmund, Sallie; Kielian, Margaret.

In: Journal of Virology, Vol. 72, No. 5, 05.1998, p. 4281-4287.

Research output: Contribution to journalArticle

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