Coronavirus envelope assembly is sensitive to changes in the terminal regions of the viral M protein.
Recently we demonstrated that the co-expressed coronavirus membrane proteins have the capacity to assemble viral envelopes which are similar to normal virus particles in dimensions and appearance, and which can form independent of a nucleocapsid (Vennema et al., 1996). For the formation of these particles only the M and the E protein are required; the S protein is dispensable but is incorporated when present. As we illustrate here, this virus-like particle assembly system is an ideal tool to study the interactions between the essential assembly partners M and E in molecular detail. Taking a mutagenetic approach we demonstrate that envelope assembly is critically sensitive to changes in the primary structure of both terminal domains of the M protein. The effects were most dramatically observed after mutation of the carboxy-terminal domain where the deletion of just one single amino acid at the extreme terminus abolished particle formation almost completely. But also some subtle mutations in the amino-terminal domain were severely inhibitory to the assembly process. Interestingly, mutant M proteins that were themselves incompetent to support particle formation appeared to inhibit, in a concentration dependent manner, the assembly of particles by wild-type M and E protein.
de Haan
C A
CA
Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Vennema
H
H
Rottier
P J
PJ
D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D000086862:Coronavirus M Proteins; D003593:Cytoplasm / Q000378:metabolism; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016296:Mutagenesis; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000502:physiology; D019065:Virus Assembly
D000086862:Coronavirus M Proteins; D014759:Viral Envelope Proteins; D014763:Viral Matrix Proteins; C088325:gene 5b protein, hepatitis virus