Fig. 7: Working model for assembly and egress of the Ff family of phages. | Nature Communications

Fig. 7: Working model for assembly and egress of the Ff family of phages.

From: Cryo-electron microscopy of the f1 filamentous phage reveals insights into viral infection and assembly

Fig. 7

The phage used in the model is depicted as per Fig. 6. OM, outer membrane; CM, cytoplasmic membrane. (1) ssDNA is packaged by pV, leaving the packaging signal hairpin exposed (green). (2) pV targets the DNA-protein complex to pI/pXI, where pV is replaced by the pVII/pIX round tip. Displacement of pV allows pVIII to diffuse laterally around the DNA. (3) ATP hydrolysis by pI/pXI drives growth of the filament with continuous addition of pVIII. (4) On reaching the terminus of DNA, pI/pXI undergoes a conformational change which increases affinity for the pIII/pVI tip, which forms a membrane-bound complex (5). (6) The L4 linker closes around the body of the phage at the H1 β-hairpin loop (Fig. 6b) and the C domain of pIII folds down over the hydrophobic helices of pVI to secede the phage from the cytoplasmic membrane. (7) Phage passes through the pIV secretin complex (mauve) in the outer membrane and is released. The flexible linkers and N0 domains aligning pIV with the pI/pXI complex shown in Fig. 1 have been omitted for clarity.

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