6gsi | pdb_00006gsi
Feline Calicivirus Strain F9 bound to a soluble ectodomain fragment of feline junctional adhesion molecule A - leading to assembly of a portal structure at a unique three-fold axis.
Structural highlights
Function[CAPSD_FCVF9] Capsid protein self assembles to form an icosahedral capsid with a T=3 symmetry, about 38 nm in diameter, and consisting of 180 capsid proteins. A smaller form of capsid with a diameter of 23 nm might be capsid proteins assembled as icosahedron with T=1 symmetry. The capsid encapsulate the genomic RNA and VP2 proteins. Attaches virion to target cells by binding to feline junctional adhesion molecule A (F11R) and/or to alpha-2,6-linked sialic acid. Once attached, the virion is endocytosed. Acidification of the endosome induces conformational change of capsid protein thereby injecting virus genomic RNA into host cytoplasm. [VP2_FCVF9] Minor structural protein present in one or two copies per virion. Does not seem to play a role in capsid assembly, but is essential for production of infectious virus (By similarity). [JAM1_FELCA] Seems to play a role in epithelial tight junction formation. Appears early in primordial forms of cell junctions and recruits PARD3. The association of the PARD6-PARD3 complex may prevent the interaction of PARD3 with JAM1, thereby preventing tight junction assembly. Plays a role in regulating monocyte transmigration involved in integrity of epithelial barrier. Ligand for integrin alpha-L/beta-2 involved in memory T-cell and neutrophil transmigration. Involved in platelet activation.[UniProtKB:O88792][UniProtKB:Q9Y624] (Microbial infection) May act as a cellular receptor for calicivirus.[1] [2] (Microbial infection) In case of orthoreovirus infection, serves as receptor for the virus.[3] Publication Abstract from PubMedTo initiate infection, many viruses enter their host cells by triggering endocytosis following receptor engagement. However, the mechanisms by which non-enveloped viruses escape the endosome are poorly understood. Here we present near-atomic-resolution cryo-electron microscopy structures for feline calicivirus both undecorated and labelled with a soluble fragment of its cellular receptor, feline junctional adhesion molecule A. We show that VP2, a minor capsid protein encoded by all caliciviruses(1,2), forms a large portal-like assembly at a unique three-fold axis of symmetry, following receptor engagement. This assembly-which was not detected in undecorated virions-is formed of twelve copies of VP2, arranged with their hydrophobic N termini pointing away from the virion surface. Local rearrangement at the portal site leads to the opening of a pore in the capsid shell. We hypothesize that the portal-like assembly functions as a channel for the delivery of the calicivirus genome, through the endosomal membrane, into the cytoplasm of a host cell, thereby initiating infection. VP2 was previously known to be critical for the production of infectious virus(3); our findings provide insights into its structure and function that advance our understanding of the Caliciviridae. Calicivirus VP2 forms a portal-like assembly following receptor engagement.,Conley MJ, McElwee M, Azmi L, Gabrielsen M, Byron O, Goodfellow IG, Bhella D Nature. 2019 Jan;565(7739):377-381. doi: 10.1038/s41586-018-0852-1. Epub 2019 Jan, 9. PMID:30626974[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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