Figure 13-3: Schematic representation of the PRD1 life cycle. The vertex associated spike-complex (comprised of proteins P31, P5, and P2; see Figure 13-2) binds to the IncP plasmid-encoded DNA transfer complex (upper left panel). The sequential steps of genome delivery are shown in the upper right panel (A-E). Receptor binding signals to the DNA delivery apparatus (containing at least proteins P7, P11, P14, P18, and P32) leading to considerable conformational changes in the vertex structure (A). The removal of the spike complex creates an opening in the vertex, which enables an appendage to protrude (protein P11) that penetrates the OM (B). The lytic transglycosylase (P7) is thought to assist in genome entry by locally degrading the peptidoglycan layer (C). The appendage formed extends some 35 nm (the thickness of the cell envelope) penetrating the CM (D). The DNA translocation in dependent on active membrane tube formation and reduction of the membrane vesicle volume assisted by at least proteins P14, P18, and P32 (E). After DNA injection, protein-primed genome replication, transcription, and translation take place. Upon translation, the major capsid protein P3 accumulates as trimers in the host cytosol whereas those phage proteins associated with the virus membrane in the mature virion are addressed to the host cell CM. Particle assembly is assisted by the host GroEL/ES complex and three phage-encoded assembly factors, the membrane-bound P10, and the soluble P17 and P33. Upon particle formation the phage-specific membrane is pinched-off from the host CM by the action of the scaffold protein P10 and the major coat protein P3. The minor capsid protein P30 enables the formation of an empty prohead by stabilizing the P3 interactions. The phage DNA is packaged into proheads by the packaging ATPase P9 through a unique vertex and mature virions are released upon lysis of the host cell caused by the phage-encoded muramidase P15 and holin protein P35.