title: Efficient DNA packaging of bacteriophage PRD1 requires the unique vertex protein P6.
abstract: The assembly of bacteriophage PRD1 proceeds via formation of empty procapsids containing an internal lipid membrane, into which the linear double-stranded DNA genome is subsequently packaged. The packaging ATPase P9 and other putative packaging proteins have been shown to be located at a unique vertex of the PRD1 capsid. Here, we describe the isolation and characterization of a suppressor-sensitive PRD1 mutant deficient in the unique vertex protein P6. Protein P6 was found to be an essential part of the PRD1 packaging machinery; its absence leads to greatly reduced packaging efficiency. Lack of P6 was not found to affect particle assembly, because in the P6-deficient mutant infection, wild-type (wt) amounts of particles were produced, although most were empty. P6 was determined not to be a specificity factor, as the few filled particles seen in the P6-deficient infection contained only PRD1-specific DNA. The presence of P6 was not necessary for retention of DNA in the capsid once packaging had occurred, and P6-deficient DNA-containing particles were found to be stable and infectious, albeit not as infectious as wt PRD1 virions. A packaging model for bacteriophage PRD1, based on previous results and those obtained in this study, is presented.
authors.affiliation: Department of Biological and Environmental Science, Institute of Biotechnology, University of Helsinki, Biocenter 2, Viikinkaari 5, FIN-00014 University of Helsinki, Finland.
authors.forename: Nelli J
authors.initials: NJ
authors.lastname: Karhu
authors.forename: Gabija
authors.initials: G
authors.lastname: Ziedaite
authors.forename: Dennis H
authors.initials: DH
authors.lastname: Bamford
authors.forename: Jaana K H
authors.initials: JK
authors.lastname: Bamford
mesh_terms: D025622:Bacteriophage PRD1 / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D042003:DNA Packaging; D009154:Mutation; D019779:Salmonella enterica / Q000648:ultrastructure / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure; D019065:Virus Assembly
chemical_list: D014764:Viral Proteins; C413452:phage phi29 protein p6