| Function |
Capsid protein VP1: Capsid proteins VP1, VP2, and VP3 form a closed capsid enclosing the viral positive strand RNA genome. All these proteins contain a beta-sheet structure called beta-barrel jelly roll. Together they form an icosahedral capsid (T=3) composed of 60 copies of each VP1, VP2, and VP3, with a diameter of approximately 300 Angstroms. VP1 is situated at the 12 fivefold axes, whereas VP2 and VP3 are located at the quasi-sixfold axes. The naked capsid interacts with the host receptor HAVCR1 to provide virion attachment to and probably entry into the target cell. Capsid protein VP2: Capsid proteins VP1, VP2, and VP3 form a closed capsid enclosing the viral positive strand RNA genome. All these proteins contain a beta-sheet structure called beta-barrel jelly roll. Together they form an icosahedral capsid (T=3) composed of 60 copies of each VP1, VP2, and VP3, with a diameter of approximately 300 Angstroms. VP1 is situated at the 12 fivefold axes, whereas VP2 and VP3 are located at the quasi-sixfold axes. The naked capsid interacts with the host receptor HAVCR1 to provide virion attachment to and probably entry into the target cell. Capsid protein VP3: Capsid proteins VP1, VP2, and VP3 form a closed capsid enclosing the viral positive strand RNA genome. All these proteins contain a beta-sheet structure called beta-barrel jelly roll. Together they form an icosahedral capsid (T=3) composed of 60 copies of each VP1, VP2, and VP3, with a diameter of approximately 300 Angstroms. VP1 is situated at the 12 fivefold axes, whereas VP2 and VP3 are located at the quasi-sixfold axes. The naked capsid interacts with the host receptor HAVCR1 to provide virion attachment to and probably entry into the target cell. Capsid protein VP0: VP0 precursor is a component of the immature procapsids. Capsid protein VP4: Plays a role in the assembly of the 12 pentamers into an icosahedral structure. Has not been detected in mature virions, supposedly owing to its small size. Protein VP1-2A: Precursor component of immature procapsids that corresponds to an extended form of the structural protein VP1. After maturation, possibly by the host Cathepsin L, the assembly signal 2A is cleaved to give rise to the mature VP1 protein. Protein 2B: Functions as a viroporin. Affects membrane integrity and causes an increase in membrane permeability. Involved in host intracellular membrane rearrangements probably to give rise to the viral factories. Does not disrupt calcium homeostasis or glycoprotein trafficking. Antagonizes the innate immune response of the host by suppressing IFN-beta synthesis, which it achieves by interfering with the DDX58/IFIH1 (RIG-I/MDA5) pathway. Protein 2BC: Affects membrane integrity and causes an increase in membrane permeability. Protein 2C: Associates with and induces structural rearrangements of intracellular membranes. Displays RNA-binding activity. Protein 3ABC: The precursor 3ABC is targeted to the mitochondrial membrane where protease 3C activity cleaves and inhibits the host antiviral protein MAVS, thereby disrupting activation of IRF3 through the IFIH1/MDA5 pathway. In vivo, the protease activity of 3ABC precursor is more efficient in cleaving the 2BC precursor than that of protein 3C. The 3ABC precursor may therefore play a role in the proteolytic processing of the polyprotein. Possible viroporin. Protein 3AB: Interacts with the 3CD precursor and with RNA structures found at both the 5'- and 3'-termini of the viral genome. Since the 3AB precursor contains the hydrophobic domain 3A, it probably anchors the whole viral replicase complex to intracellular membranes on which viral RNA synthesis occurs. Protein 3A: May serve as membrane anchor to the 3AB and 3ABC precursors via its hydrophobic domain. May interact with RNA. 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 VPg-pUpU is then used as primer on the genomic RNA poly(A) by the RNA-dependent RNA polymerase to replicate the viral genome. Protease 3C: Cysteine protease that generates mature viral proteins from the precursor polyprotein. In addition to its proteolytic activity, it binds to viral RNA, and thus influences viral genome replication. RNA and substrate bind cooperatively to the protease. Cleaves IKBKG/NEMO to impair innate immune signaling. Cleaves host PABPC1 which may participate in the switch of viral translation to RNA synthesis. Protein 3CD: Interacts with the 3AB precursor and with RNA structures found at both the 5'- and 3'-termini of the viral genome. Disrupts TLR3 signaling by degrading the host adapter protein TICAM1/TRIF. RNA-directed RNA polymerase 3D-POL replicates genomic and antigenomic RNA by recognizing replications specific signals.
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