title: Proteolytic cleavage of the murine coronavirus surface glycoprotein is not required for its fusion activity.
abstract: The surface glycoprotein (S) of the murine hepatitis coronavirus MHV normally undergoes proteolytic cleavage during transport to the cell surface. To determine whether the cleavage of the MHV-JHM S glycoprotein is required to activate its ability to fuse cellular membranes, the protease recognition sequence in a cDNA copy of the S gene was altered from Arg-Arg-Ala-Arg-Arg into Ser-Val-Ser-Gly-Gly by site directed mutagenesis. The mutated and wild type S genes were expressed by means of recombinant vaccinia viruses and it could be shown that the mutated S protein was not cleaved when it was expressed in mouse DBT cells, in contrast to the wild type S protein. Nevertheless, the non-cleaved S protein induced extensive syncytium formation in mouse DBT cells. 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 its fusion function.
authors.affiliation: Institut für Virologie, Universität Würzburg.
authors.forename: R
authors.initials: R
authors.lastname: Stauber
authors.forename: M
authors.initials: M
authors.lastname: Pfleiderer
authors.forename: S
authors.initials: S
authors.lastname: Siddell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001254:Astrocytoma; D002459:Cell Fusion; D003588:Cytopathogenic Effect, Viral; D010450:Endopeptidases / Q000378:metabolism; D006367:HeLa Cells / Q000382:microbiology; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000235:genetics / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D064370:Spike Glycoprotein, Coronavirus; D014407:Tumor Cells, Cultured / Q000382:microbiology; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus; D010450:Endopeptidases