 Under the lipid membrane is a matrix protein (M); it forms the inner layer of the virus envelope and stabilizes it structure.The SeV virion also contains the nucleocapsid core, which is composed of the genomic RNA, the nucleocapsid protein (NP), the phosphoproteins (P), which is an essential subunit of the viral of RNA-dependent RNA polymerase (RDRP), and the large protein (L) that is a catalytic subunit of this polymerase.C-protein, which is translated from an alternative reading frame of the P-coding mRNA, is also associated with a viral capsid.