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The structure of coxsackievirus A16 mature virion in complex with Fab 8C4
Structural highlights
FunctionM4TAU2_9ENTO 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 (By similarity). 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 (By similarity). Following genome release from the infecting virion in the cytoplasm, the VPg-RNA linkage is probably removed by host TDP2 (By similarity). During the late stage of the replication cycle, host TDP2 is excluded from sites of viral RNA synthesis and encapsidation, allowing for the generation of progeny virions.[ARBA:ARBA00024846] 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.[RuleBase:RU364118] 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.[RuleBase:RU364118] 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.[RuleBase:RU364118] 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.[RuleBase:RU364118] 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.[RuleBase:RU364118] Component of immature procapsids, which is cleaved into capsid proteins VP4 and VP2 after maturation (By similarity). Allows the capsid to remain inactive before the maturation step.[ARBA:ARBA00025202] Forms an icosahedral capsid of pseudo T=3 symmetry with capsid proteins VP2 and VP3 (By similarity). The capsid is 300 Angstroms in diameter, composed of 60 copies of each capsid protein and enclosing the viral positive strand RNA genome.[ARBA:ARBA00025306] Lies on the inner surface of the capsid shell (By similarity). After binding to the host receptor, the capsid undergoes conformational changes (By similarity). 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.[ARBA:ARBA00024643] Protease 2A: Cysteine protease that cleaves viral polyprotein and specific host proteins.[RuleBase:RU364118] Protease 3C: Major viral protease that mediates proteolytic processing of the polyprotein. Cleaves host EIF5B, contributing to host translation shutoff. Cleaves also host PABPC1, contributing to host translation shutoff.[RuleBase:RU364118] 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 cytoplasmic calcium may trigger membrane trafficking and transport of viral ER-associated proteins to viroplasms, sites of viral genome replication.[RuleBase:RU364118] 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.[RuleBase:RU364118] 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 disassembly of the Golgi complex, possibly through GBF1 interaction. This would result in depletion of MHC, trail receptors and IFN receptors at the host cell surface.[RuleBase:RU364118] 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.[RuleBase:RU364118] Protein 3CD: 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. Protein 3CD binds to the 5'UTR of the viral genome.[RuleBase:RU364118] 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.[RuleBase:RU364118] 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.[RuleBase:RU364118] Publication Abstract from PubMedCoxsackievirus A16 (CVA16) causes hand, foot and mouth disease in infants and young children. However, no vaccine or anti-viral agent is currently available for CVA16. Here, the functions and working mechanisms of two CVA16-specific neutralizing monoclonal antibodies (MAbs), 9B5 and 8C4, are comprehensively investigated. Both 9B5 and 8C4 display potent neutralization in vitro and prophylactic and therapeutic efficacy in a mouse model of CVA16 infection. Mechanistically, 9B5 exerts neutralization primarily through inhibiting CVA16 attachment to cell surface via blockade of CVA16 binding to its attachment receptor, heparan sulfate, whereas 8C4 functions mainly at the post-attachment stage of CVA16 entry by interfering with the interaction between CVA16 and its uncoating receptor SCARB2. Cryo-EM studies show that 9B5 and 8C4 target distinct epitopes located at the 5-fold and 3-fold protrusions of CVA16 capsids, respectively, and exhibit differential binding preference to three forms of naturally occurring CVA16 particles. Moreover, 9B5 and 8C4 are compatible in formulating an antibody cocktail which displays the ability to prevent virus escape seen with individual MAbs. Together, our work elucidates the functional and structural basis of CVA16 antibody-mediated neutralization and protection, providing important information for design and development of effective CVA16 vaccines and antibody therapies. Molecular mechanism of antibody neutralization of coxsackievirus A16.,Zhang C, Liu C, Shi J, Wang Y, Xu C, Ye X, Liu Q, Li X, Qiao W, Yin Y, Cong Y, Huang Z Nat Commun. 2022 Dec 21;13(1):7854. doi: 10.1038/s41467-022-35575-w. PMID:36543790[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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