Key result
Cryo-electron microscopy reconstructions demonstrate that protein P7 is located near the three-fold axis of symmetry in the unexpanded procapsid of the φ6 cystovirus.
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Informs φ6 procapsid models; leaves open P7 functional roles pending validation studies.
The objective of this study was to determine the location of protein P7, the RNA packaging factor, in the procapsid of the φ6 cystovirus. A comparison of cryo-electron microscopy high-resolution single particle reconstructions of the φ6 complete unexpanded procapsid, the protein P2-minus procapsid (P2 is the RNA directed RNA-polymerase), and the P7-minus procapsid, show that prior to RNA packaging the P7 protein is located near the three-fold axis of symmetry. Difference maps highlight the precise position of P7 and demonstrate that in P7-minus particles the P2 proteins are less localized with reduced densities at the three-fold axes. We propose that P7 performs the mechanical function of stabilizing P2 on the inner protein P1 shell which ensures that entering viral single-stranded RNA is replicated.
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Katz et al. (2012) studied Cystovirus φ6 procapsid structure. Cryo-electron microscopy and single particle reconstruction was evaluated on Location of protein P7 in the unexpanded procapsid. Cryo-electron microscopy reconstructions demonstrate that protein P7 is located near the three-fold axis of symmetry in the unexpanded procapsid of the φ6 cystovirus.
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