Membrane (M) protein of HVJ (Sendai virus): Its role in virus assembly

The role in virus assembly of membrane or matrix (M) protein of HVJ (Sendai virus) was investigated. When virions were disrupted with alkali Tween 20, nucleocapsids with a sheathlike cover on the surface and a width of approx 33 nm were often obtained, and this sheathlike structure was composed of M protein. Selective aggregation of viral components in vitro was examined. Each viral component was isolated separately from virions by using detergents, and they were mixed with each other in various combinations. The structures which reaggregated were examined for their protein composition, and the results indicate that the nucleocapsid protein does not combine with viral glycoproteins to form a coaggregate unless M protein is present, which suggests that the M protein in vivo may be a mediator for the association of nucleocapsid with the modified areas of plasma membrane which will become viral envelope.