Tsai C.-W.SHIN CHANGMING-FU CHANG2019-08-302019-08-3019990021-9258https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033543749&doi=10.1074%2fjbc.274.37.26085&partnerID=40&md5=aa15ebd76ea5ba967f5d8d48cc370321https://scholars.lib.ntu.edu.tw/handle/123456789/416903The spike (S) glycoprotein of mouse hepatitis virus (MHV) plays a major role in the viral pathogenesis. It is often processed into the N-terminal S1 and the C-terminal S2 subunits that were evidently important for binding to cell receptor and inducing cell-cell fusion, respectively. As a consequence of cell-cell fusion, most of the naturally occurring infections of MHV are associated with syncytia formation. So far, only MHV-2 was identified to be fusion-negative. In this study, the S gene of MHV-2 was molecularly cloned, and the nucleotide sequence was determined. The MHV-2 S protein lacks a 12- amino acid stretch in the S1 hypervariable region from amino acid residue 446 to 457 when compared with the fusion-positive strain MHV-JHM. In addition, there are three amino acid substitutions in the S2 subunit, Tyr-1144 to Asp, Glu-1165 to Asp, and Arg-1209 to Lys. The cloned MHV-2 S protein exhibited the fusion-negative property in DBT cells as the intrinsic viral protein. Furthermore, similar to the fusion-positive MHV-JHM strain, proteolytic cleavage activity was detected both in DBT cells infected with the fusion- negative MHV-2 and in the transfected cells that expressed the cloned MHV-2 S protein. Domain swapping experiments demonstrated that the 12-amino acid stretch missing in the MHV-2 S1 subunit, but not the proteolytic cleavage site, was critical for the cell-fusion activity of MHV.en-US[SDGs]SDG3amino acid; protein subunit; virus glycoprotein; amino terminal sequence; animal cell; article; carboxy terminal sequence; cell fusion; controlled study; hepatitis virus; molecular cloning; mouse; nonhuman; nucleotide sequence; priority journal; protein degradation; receptor binding; sequence analysis; Animals; Base Sequence; Cell Fusion; Cell Line; Cloning, Molecular; DNA Primers; Membrane Glycoproteins; Mice; Molecular Sequence Data; Murine hepatitis virus; Sequence Deletion; Viral Envelope Proteins; Animalia; DNA viruses; Murine hepatitis virusjournal article10.1074/jbc.274.37.26085104735572-s2.0-0033543749