📄 Proteolytic cleavage of the murine coronavirus surface glycoprotein is not required for fusion activity

A cDNA copy of the murine coronavirus [otherwise known as murine hepatitis virus (MHV)] surface (S) glycoprotein gene was isolated and expressed in DBT cells by using a recombinant vaccinia virus system. The expressed S protein induced extensive syncytium formation at neutral pH. Oligonucleotide mutagenesis was used to engineer an S protein gene in which codons for the proteolytic cleavage site, Arg-Arg-Ala-Arg-Arg, were replaced with an equal number of codons for amino acids with aliphatic or aliphatic hydroxyl side-chains The mutated S protein was stably expressed in DBT cells and, in contrast to the wild-type protein, was not proteolytically cleaved. Nevertheless, the non-cleaved protein induced extensive syncytium formation. These results clearly indicate that the non-cleaved form of the MHV S protein is able to mediate cell membrane fusion. Thus proteolytic cleavage is not an absolute requirement for fusion activity.

keywords 🔗 hepatitis virus (437) 🔗 cleavage site (85) 🔗 amino acid (454) 🔗 murine hepatitis (71) 🔗 murine coronavirus (140) 🔗 amino acids (205) 🔗 membrane fusion (105)

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