PMID:1569567

Citation	Casjens, S, Wyckoff, E, Hayden, M, Sampson, L, Eppler, K, Randall, S, Moreno, ET and Serwer, P (1992) Bacteriophage P22 portal protein is part of the gauge that regulates packing density of intravirion DNA. J. Mol. Biol. 224:1055-74
Abstract	The complex double-stranded DNA bacteriophages assemble DNA-free protein shells (procapsids) that subsequently package DNA. In the case of several double-stranded DNA bacteriophages, including P22, packaging is associated with cutting of DNA from the concatemeric molecule that results from replication. The mature intravirion P22 DNA has both non-unique (circularly permuted) ends and a length that is determined by the procapsid. In all known cases, procapsids consist of an outer coat protein, an interior scaffolding protein that assists in the assembly of the coat protein shell, and a ring of 12 identical portal protein subunits through which the DNA is presumed to enter the procapsid. To investigate the role of the portal protein in cutting permuted DNA from concatemers, we have characterized P22 portal protein mutants. The effects of several single amino acid changes in the P22 portal protein on the length of the DNA packaged, the density to which DNA is condensed within the virion, and the outer radius of the capsid have been determined. The results obtained with one mutant (NT5/1a) indicate no change (+/- 0.5%) in the radius of the capsid, but mature DNA that is 4.7% longer and a packing density that is commensurately higher than those of wild-type P22. Thus, the portal protein is part of the gauge that regulates the length and packaging density of DNA in bacteriophage P22. We argue that these findings make models for DNA packaging less likely in which the packing density is a property solely of the coat protein shell or of the DNA itself.
Links	PubMed
Keywords	Base Sequence; Capsid/physiology; Capsid/ultrastructure; Capsid Proteins; Chromosome Mapping; DNA, Viral/chemistry; DNA, Viral/metabolism; Glycoproteins/physiology; Molecular Sequence Data; Morphogenesis; Mutation; Salmonella Phages/growth & development; Salmonella Phages/ultrastructure; Salmonella typhimurium/genetics; Transduction, Genetic; Viral Proteins/metabolism; Water
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPP22:PORTL		GO:0098006: viral DNA genome packaging, headful	ECO:0000315:		P		Figure 9	complete CACAO 12036

References

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