Fig. 1: Schematic of phage infection, egress and the proteins that comprise the phage capsid. | Nature Communications

Fig. 1: Schematic of phage infection, egress and the proteins that comprise the phage capsid.

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

Fig. 1

a f1 is comprised of the major capsid protein pVIII (light blue rectangles), which forms the filamentous body of the phage. The minor capsid proteins pIII (C domain orange oval, N1 domain teal circles and N2 domain light pink circles) and pVI (purple circles) form one tip, with pVII (pink oval) and pIX (yellow oval) forming the other. For clarity, only 3 pIII/pVI proteins and one each of pVII/pIX are shown, instead of 5 of each. pIII binds to the F-pilus (light green), which on retraction, ultimately allows the phage to reach the TolQRA complex anchored in the cytoplasmic membrane (shades of pink). After DNA injection and genome replication, phage proteins are expressed and assembled. pI/pXI (shades of brown) in the cytoplasmic membrane align with the outer membrane secretin pIV (mauve), potentially via the N0 domain of pIV (mauve circles), connected to the pIV barrel via flexible linkers19. Phage egress is dependent on the proton-motive force and ATP hydrolysis by pI. b Schematic to show the f1 capsid proteins and their domains. The numbering for the pIII and pVIII precursor proteins is shown, alongside the numbering for the mature proteins (bold). The domains of pIII are coloured as follows: N1 (teal), N2 (light pink), C (orange) and glycine-rich linkers (brown). We have used the numbering for the mature protein throughout the manuscript. SS signal sequence.

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