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Lam Emmett Lisal Kainov Tuma FSU This virus is activated by single-stranded RNA entering through a pore.
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The inner pore consists of a hexamer (34 kDa each) ATPase that powers the "motor" that propels the RNA through the pore.
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The structure of the pore hexamer protein (P4) assembly is known (at least for a homologous virus) from x-ray analysis
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5’ P4 P1
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Translocation direction
Orientation of P4 within its Procapsid Translocation direction Capsid Interior
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Orientation of P4 within its Procapsid
Translocation direction Capsid Interior However which end of the pore faces the outside was not known
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P4 Alone P4 in Procapsid H/D Exchange Rate < 0.1 h-1
0.1 h h-1 1 h h-1 10 h h-1 > 100 h-1 P4 Alone P4 in Procapsid
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H/D Exchange Rate Study
Apical domain P4 Alone C-terminus > 100 h-1 P4 in Procapsid 1 h h-1 10 h h-1 The C-terminus loses some solvent accessibility on binding to the virus.
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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
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The affected peptide resides in the hydrophobic core
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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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