Assembly of spikes into coronavirus particles is mediated by the carboxy-terminal domain of the spike protein.
The type I glycoprotein S of coronavirus, trimers of which constitute the typical viral spikes, is assembled into virions through noncovalent interactions with the M protein. Here we demonstrate that incorporation is mediated by the short carboxy-terminal segment comprising the transmembrane and endodomain. To this aim, we used the virus-like particle (VLP) system that we developed earlier for the mouse hepatitis virus strain A59 (MHV-A59) and which we describe now also for the unrelated coronavirus feline infectious peritonitis virus (FIPV; strain 79-1146). Two chimeric MHV-FIPV S proteins were constructed, consisting of the ectodomain of the one virus and the transmembrane and endodomain of the other. These proteins were tested for their incorporation into VLPs of either species. They were found to assemble only into viral particles of the species from which their carboxy-terminal domain originated. Thus, the 64-terminal-residue sequence suffices to draw the 1308 (MHV)- or 1433 (FIPV)-amino-acid-long mature S protein into VLPs. Both chimeric S proteins appeared to cause cell fusion when expressed individually, suggesting that they were biologically fully active. This was indeed confirmed by incorporating one of the proteins into virions which thereby acquired a new host cell tropism, as will be reported elsewhere.
Godeke
G J
GJ
Institute of Virology, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, and Institute of Biomembranes, Utrecht University, 3584 CL Utrecht, The Netherlands.
de Haan
C A
CA
Rossen
J W
JW
Vennema
H
H
Rottier
P J
PJ
D000595:Amino Acid Sequence; D000818:Animals; D002415:Cats; D002459:Cell Fusion; D002460:Cell Line; D017934:Coronavirus / Q000235:genetics / Q000378:metabolism*; D016765:Coronavirus, Feline / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000378:metabolism*; D014771:Virion / Q000378:metabolism*; D019065:Virus Assembly
D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus