Function:
Capsid protein VP1: Forms an icosahedral capsid of pseudo T=3 symmetry with capsid proteins VP2 and VP3. The capsid is 300 Angstroms in diameter, composed of 60 copies of each capsid protein and enclosing the viral positive strand RNA genome. Capsid protein VP1 mainly forms the vertices of the capsid. Capsid protein VP1 interacts with host cell receptor to provide virion attachment to target host cells. This attachment induces virion internalization. Tyrosine kinases are probably involved in the entry process. After binding to its receptor, the capsid undergoes conformational changes. Capsid protein VP1 N-terminus (that contains an amphipathic alpha-helix) and capsid protein VP4 are externalized. Together, they shape a pore in the host membrane through which viral genome is translocated to host cell cytoplasm. After genome has been released, the channel shrinks.
Capsid protein VP2: Forms an icosahedral capsid of pseudo T=3 symmetry with capsid proteins VP2 and VP3. The capsid is 300 Angstroms in diameter, composed of 60 copies of each capsid protein and enclosing the viral positive strand RNA genome.
Capsid protein VP3: Forms an icosahedral capsid of pseudo T=3 symmetry with capsid proteins VP2 and VP3. The capsid is 300 Angstroms in diameter, composed of 60 copies of each capsid protein and enclosing the viral positive strand RNA genome.
Capsid protein VP4: Lies on the inner surface of the capsid shell. After binding to the host receptor, the capsid undergoes conformational changes. Capsid protein VP4 is released, Capsid protein VP1 N-terminus is externalized, and together, they shape a pore in the host membrane through which the viral genome is translocated into the host cell cytoplasm. After genome has been released, the channel shrinks.
Capsid protein VP0: Component of immature procapsids, which is cleaved into capsid proteins VP4 and VP2 after maturation. Allows the capsid to remain inactive before the maturation step.
Protein 2A: Cysteine protease that cleaves viral polyprotein and specific host proteins. It is responsible for the cleavage between the P1 and P2 regions, first cleavage occurring in the polyprotein. Cleaves also the host translation initiation factor EIF4G1, in order to shut down the capped cellular mRNA translation. Inhibits the host nucleus-cytoplasm protein and RNA trafficking by cleaving host members of the nuclear pores.
Protein 2B: Plays an essential role in the virus replication cycle by acting as a viroporin. Creates a pore in the host reticulum endoplasmic and as a consequence releases Ca2+ in the cytoplasm of infected cell. In turn, high levels of cyctoplasmic calcium may trigger membrane trafficking and transport of viral ER-associated proteins to viroplasms, sites of viral genome replication.
Protein 2C: Induces and associates with structural rearrangements of intracellular membranes. Displays RNA-binding, nucleotide binding and NTPase activities. May play a role in virion morphogenesis and viral RNA encapsidation by interacting with the capsid protein VP3 (By similarity). {ECO:0000250}.
Protein 3AB: Localizes the viral replication complex to the surface of membranous vesicles. Together with protein 3CD binds the Cis-Active RNA Element (CRE) which is involved in RNA synthesis initiation. Acts as a cofactor to stimulate the activity of 3D polymerase, maybe through a nucleid acid chaperone activity.
Protein 3A: Localizes the viral replication complex to the surface of membranous vesicles. It inhibits host cell endoplasmic reticulum-to-Golgi apparatus transport and causes the dissassembly of the Golgi complex, possibly through GSF1 interaction. This would result in depletion of MHC, trail receptors and IFN receptors at the host cell surface.
Viral protein genome-linked: acts as a primer for viral RNA replication and remains covalently bound to viral genomic RNA. VPg is uridylylated prior to priming replication into VPg-pUpU. The oriI viral genomic sequence may act as a template for this. The VPg-pUpU is then used as primer on the genomic RNA poly(A) by the RNA-dependent RNA polymerase to replicate the viral genome. VPg may be removed in the cytoplasm by an unknown enzyme termed 'unlinkase'. VPg is not cleaved off virion genomes because replicated genomic RNA are encapsidated at the site of replication.
Protein 3CD: Is involved in the viral replication complex and viral polypeptide maturation. It exhibits protease activity with a specificity and catalytic efficiency that is different from protease 3C. Protein 3CD lacks polymerase activity. The 3C domain in the context of protein 3CD may have an RNA binding activity.
Protease 3C: cleaves host DDX58/RIG-I and thus contributes to the inhibition of type I interferon production. Cleaves also host PABPC1.
RNA-directed RNA polymerase: Replicates the viral genomic RNA on the surface of intracellular membranes. May form linear arrays of subunits that propagate along a strong head-to-tail interaction called interface-I. Covalently attaches UMP to a tyrosine of VPg, which is used to prime RNA synthesis. The positive stranded RNA genome is first replicated at virus induced membranous vesicles, creating a dsRNA genomic replication form. This dsRNA is then used as template to synthesize positive stranded RNA genomes. ss(+)RNA genomes are either translated, replicated or encapsidated.
Subunit:
Capsid protein VP1: Interacts with capsid protein VP0, and capsid protein VP3 to form heterotrimeric protomers. Five protomers subsequently associate to form pentamers which serve as building blocks for the capsid. Interacts with capsid protein VP4 in the mature capsid. Capsid protein VP0: interacts with capsid protein VP1 and capsid protein VP3 to form heterotrimeric protomers. Five protomers subsequently associate to form pentamers which serve as building blocks for the capsid. Capsid protein VP2: Interacts with capsid protein VP1 and capsid protein VP3 in the mature capsid. Capsid protein VP3: interacts with capsid protein VP0 and capsid protein VP1 to form heterotrimeric protomers. Five protomers subsequently associate to form pentamers which serve as building blocks for the capsid. Interacts with capsid protein VP4 in the mature capsid. Capsid protein VP4: Interacts with capsid protein VP1 and capsid protein VP3. Protein 2C: interacts with capsid protein VP3; this interaction may be important for virion morphogenesis. Protein 3AB: interacts with protein 3CD. Viral protein genome-linked: interacts with RNA-directed RNA polymerase. Protein 3CD: interacts with protein 3AB and with RNA-directed RNA polymerase. RNA-directed RNA polymerase: interacts with viral protein genome-linked and with protein 3CD.
Subcellular Location:
Capsid protein VP0: Virion {ECO:0000250}. Host cytoplasm {ECO:0000250}.
Capsid protein VP4: Virion {ECO:0000250}.
Capsid protein VP2: Virion {ECO:0000250}. Host cytoplasm {ECO:0000250}.
Capsid protein VP3: Virion {ECO:0000250}. Host cytoplasm {ECO:0000250}.
Capsid protein VP1: Virion {ECO:0000250}. Host cytoplasm {ECO:0000250}.
Protein 2B: Host cytoplasmic vesicle membrane {ECO:0000305}; Peripheral membrane protein {ECO:0000305}; Cytoplasmic side {ECO:0000305}. Note=Probably localizes to the surface of intracellular membrane vesicles that are induced after virus infection as the site for viral RNA replication. These vesicles are derived from the endoplasmic reticulum.
Protein 2C: Host cytoplasmic vesicle membrane {ECO:0000305}; Peripheral membrane protein {ECO:0000305}; Cytoplasmic side {ECO:0000305}. Note=Probably localizes to the surface of intracellular membrane vesicles that are induced after virus infection as the site for viral RNA replication. These vesicles are derived from the endoplasmic reticulum.
Protein 3A: Host cytoplasmic vesicle membrane {ECO:0000305}; Peripheral membrane protein {ECO:0000305}; Cytoplasmic side {ECO:0000305}. Note=Probably localizes to the surface of intracellular membrane vesicles that are induced after virus infection as the site for viral RNA replication. These vesicles are derived from the endoplasmic reticulum.
Protein 3AB: Host cytoplasmic vesicle membrane {ECO:0000305}; Peripheral membrane protein {ECO:0000305}; Cytoplasmic side {ECO:0000305}. Note=Probably localizes to the surface of intracellular membrane vesicles that are induced after virus infection as the site for viral RNA replication. These vesicles are derived from the endoplasmic reticulum.
Viral protein genome-linked: Virion. Host cytoplasm {ECO:0000250}.
Protease 3C: Host cytoplasm {ECO:0000250}.
Protein 3CD: Host cytoplasmic vesicle membrane {ECO:0000305}; Peripheral membrane protein {ECO:0000305}; Cytoplasmic side {ECO:0000305}. Note=Probably localizes to the surface of intracellular membrane vesicles that are induced after virus infection as the site for viral RNA replication. These vesicles are derived from the endoplasmic reticulum.
RNA-directed RNA polymerase: Host cytoplasmic vesicle membrane {ECO:0000305}; Peripheral membrane protein {ECO:0000305}; Cytoplasmic side {ECO:0000305}. Note=Probably localizes to the surface of intracellular membrane vesicles that are induced after virus infection as the site for viral RNA replication. These vesicles are derived from the endoplasmic reticulum.
Post-translational modifications:
Specific enzymatic cleavages in vivo by the viral proteases yield a variety of precursors and mature proteins. Polyprotein processing intermediates such as VP0 which is a VP4-VP2 precursor are produced. During virion maturation, non-infectious particles are rendered infectious following cleavage of VP0. This maturation cleavage is followed by a conformational change of the particle.
VPg is uridylylated by the polymerase and is covalently linked to the 5'-end of genomic RNA. This uridylylated form acts as a nucleotide-peptide primer for the polymerase.
Myristoylation of VP4 is required during RNA encapsidation and formation of the mature virus particle.
Capsid protein VP0: Myristoylation is required for the formation of pentamers during virus assembly. Further assembly of 12 pentamers and a molecule of genomic RNA generates the provirion.
Genome polyprotein: Specific enzymatic cleavages in vivo by the viral proteases yield processing intermediates and the mature proteins.
Capsid protein VP0: During virion maturation, immature virions are rendered infectious following cleavage of VP0 into VP4 and VP2. This maturation seems to be an autocatalytic event triggered by the presence of RNA in the capsid and it is followed by a conformational change infectious virion.
Viral protein genome-linked: VPg is uridylylated by the polymerase into VPg-pUpU. This acts as a nucleotide-peptide primer for the genomic RNA replication
Similarity:
Belongs to the picornaviruses polyprotein family.
Contains 1 peptidase C3 domain. {ECO:0000305}.
Contains 1 RdRp catalytic domain.
Contains 1 SF3 helicase domain.
Database links:
UniProtKB - Q9QF31 (POLG_CX16T)
Important Note:
This product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications.
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