Outer capsid protein Mu1/VP4 (IPR009113)

Short name: Mu1/VP4

Overlapping homologous superfamilies

Family relationships



This entry includes the outer capsid protein Mu1 and VP4.

Mu1 is an outer capsid protein that acts as a reoviral penetration agent. Non-enveloped animal reoviruses must enter host cells by membrane penetration that does not involve membrane fusion, as they lack a viral membrane. Reoviruses are activated by proteolytic cleavage in the intestinal lumen, leading to infectious subviral particles. The core of the virus is coated by a layer of mu1 and sigma3 proteins. Proteases strip off sigma3 exposing mu1, which provides the membrane penetration machinery that perforates the membrane. In addition, N-terminal myristoylation of polypeptide Mu1 are required for site-specific cleavage to Mu1C in transfected cells [PMID: 1548757]. Mu1 forms a trimer, where the three mu1 molecules are coiled around one another with a right-handed twist. The mu1 chain folds into four distinct domains: three intertwined, predominantly alpha helical domains and a jelly-roll beta-sandwich [PMID: 11832217].

VP4 nteracts with VP7 to form the outer icosahedral capsid with an incomplete T=13 symmetry, about 80 nm in diameter, and consisting of 200 VP4-VP7 trimers. Its myristoylated N-terminal peptide may be released in the endosome and involved in permeabilization and delivery of transcriptionally active viral particles into the host cell cytoplasm [PMID: 18625243, PMID: 2153941].

GO terms

Biological Process

GO:0009405 pathogenesis
GO:0046718 viral entry into host cell

Molecular Function

GO:0046812 host cell surface binding

Cellular Component

GO:0039624 viral outer capsid

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.