Figure 12-3: Life cycle of filamentous phage f1/M13/fd. The phage (via pIII, located at one end) binds to the tip of the F-pilus. Pilus retraction brings the phage close to the cell surface where pIII then binds to the periplasmic domain of host TolA. The cytoplasmic membrane-anchored TolA, Q and R proteins mediate depolymerization of the phage coat proteins into the membrane (where they are available for re-utilization) and entry of the phage circular ssDNA into the cytoplasm. The ssDNA is converted to a double-stranded, super-coiled replicative form by the action of host RNA polymerase, DNA polymerase III, and gyrase. Super-coiled RF is a template for phage gene expression and rolling circle replication, which generates a single-stranded DNA molecule. When sufficient pV has accumulated, pV dimers cover the ssDNA, leaving the PS hairpin exposed at one end; the pV-ssDNA complex is a substrate for assembly. The five coat proteins are integral cytoplasmic membrane proteins prior to their incorporation into the phage particle. (for better image quality, click here for tif image, which may be quite large; may also require screen refreshing plus special software to view; or view larger tif in separate window)

Figure 12-1, Figure 12-2, Figure 12-3, Figure 12-4, Figure 12-5, Figure 12-6

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