title: Bacteriophage phi 29 proteins required for in vitro DNA-gp3 packaging.
abstract: In vitro assembly of bacteriophage phi 29 in crude extracts involves efficient packaging of a DNA-protein complex (DNA- gp3 ) into a prohead with the aid of the gene 16 product ( gp16 ) and subsequent assembly of neck and tail proteins ( Bjornsti et al., J. Virol. 41:508-517, 1982; Bjornsti et al., J. Virol. 45:383-396, 1983; Bjornsti et al., Proc. Natl. Acad. Sci. U.S.A. 78:5861-5865, 1981). To define the viral proteins required for the DNA- gp3 encapsidation phase, we purified biologically active proheads and DNA- gp3 and constructed a chimeric plasmid, pUM101 , which contained and expressed gene 16 of phi 29 and no other viral genes. The plasmid-specified gp16 was both necessary and sufficient to package 24% of the DNA- gp3 added to the purified proheads , and the DNA-filled heads so produced were efficiently complemented to infectious phage by the addition of neck and tail proteins. Purified proheads and DNA- gp3 gave linear dose-response curves with slopes of approximately 1; in contrast, a 4-fold dilution of gp16 resulted in a 1,000-fold reduction of phi 29, suggesting a requirement for multiple copies of this protein.
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics*; D001435:Bacteriophages / Q000235:genetics*; D004261:DNA Replication; D004279:DNA, Viral / Q000235:genetics*; D005796:Genes; D005814:Genes, Viral; D005816:Genetic Complementation Test; D007700:Kinetics; D008970:Molecular Weight; D014764:Viral Proteins / Q000235:genetics*; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins