Rescue of maturation off-pathway products in the assembly of Pseudomonas phage φ 6.

Many complex viruses use an assembly pathway in which their genome is packaged into an empty procapsid which subsequently matures into its final expanded form. We utilized Pseudomonas phage 6, a well-established virus assembly model, to probe the plasticity of the procapsid maturation pathway. The 6 packaging nucleoside triphosphatase (NTPase), which powers sequential translocation of the three viral genomic single-stranded RNA molecules to the procapsid during capsid maturation, is part of the mature 6 virion but may spontaneously be dissociated from the procapsid shell.

Nonspecific nucleoside triphosphatase P4 of double-stranded RNA bacteriophage phi6 is required for single-stranded RNA packaging and transcription.

Bacteriophage phi6 has a segmented double-stranded RNA genome. The genomic single-stranded RNA (ssRNA) precursors are packaged into a preformed protein capsid, the polymerase complex, composed of viral proteins P1, P2, P4, and P7. Packaging of the genomic precursors is an energy-dependent process requiring nucleoside triphosphates.