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This virus is activated by single-stranded RNA entering through a pore.

Explore the structure and function of the pore hexamer protein in a virus activated by single-stranded RNA. Learn about the ATPase motor driving RNA translocation and how the RNA squeezes through the pore. Discover insights from x-ray analysis and H/D exchange studies on RNA loading and packaging initiation mechanisms.

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This virus is activated by single-stranded RNA entering through a pore.

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  1. Lam Emmett Lisal Kainov Tuma FSU This virus is activated by single-stranded RNA entering through a pore.

  2. The inner pore consists of a hexamer (34 kDa each) ATPase that powers the "motor" that propels the RNA through the pore. 

  3. The structure of the pore hexamer protein (P4) assembly is known (at least for a homologous virus) from x-ray analysis

  4. 5’ P4 P1

  5. Orientation of P4 within its Procapsid Translocation direction Capsid Interior

  6. Orientation of P4 within its Procapsid Translocation direction Capsid Interior However which end of the pore faces the outside was not known

  7. H/D Exchange Rate < 0.1 h-1 0.1 h-1 - 1 h-1 1 h-1 - 10 h-1 10 h-1 - 100 h-1 > 100 h-1 P4 Alone P4 in Procapsid

  8. Apical domain H/D Exchange Rate Study P4 Alone C-terminus > 100 h-1 P4 in Procapsid 1 h-1 - 10 h-1 10 h-1 - 100 h-1 The C-terminus loses some solvent accessibility on binding to the virus.

  9. The next question is, how does RNA squeeze through the pore on addition of ATP? • H/D exchange studies were performed on the pore hexamer: • in the free state • in the presence of ATP • in the presence of RNA • in the presence of both ATP and RNA

  10. The affected peptide resides in the hydrophobic core

  11. Mechanism of RNA loading during the initiation of packaging involves RNA-induced ring opening Surprisingly, RNA does not pry open the pore to make it wider. Rather the RNA squeezes between adjacent protein aceous monomeric components of the hexamer and then threads through the central hole.

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