PMID:12239300

Citation	Moore, SD and Prevelige, PE Jr (2002) A P22 scaffold protein mutation increases the robustness of head assembly in the presence of excess portal protein. J. Virol. 76:10245-55
Abstract	Bacteriophage with linear, double-stranded DNA genomes package DNA into preassembled protein shells called procapsids. Located at one vertex in the procapsid is a portal complex composed of a ring of 12 subunits of portal protein. The portal complex serves as a docking site for the DNA packaging enzymes, a conduit for the passage of DNA, and a binding site for the phage tail. An excess of the P22 portal protein alters the assembly pathway of the procapsid, giving rise to defective procapsid-like particles and aberrant heads. In the present study, we report the isolation of escape mutant phage that are able to replicate more efficiently than wild-type phage in the presence of excess portal protein. The escape mutations all mapped to the same phage genome segment spanning the portal, scaffold, coat, and open reading frame 69 genes. The mutations present in five of the escape mutants were determined by DNA sequencing. Interestingly, each mutant contained the same mutation in the scaffold gene, which changes the glycine at position 287 to glutamate. This mutation alone conferred an escape phenotype, and the heads assembled by phage harboring only this mutation had reduced levels of portal protein and exhibited increased head assembly fidelity in the presence of excess portal protein. Because this mutation resides in a region of scaffold protein necessary for coat protein binding, these findings suggest that the P22 scaffold protein may define the portal vertices in an indirect manner, possibly by regulating the fidelity of coat protein polymerization.
Links	PubMed PMC136566
Keywords	Bacteriophage P22/genetics; Bacteriophage P22/metabolism; Bacteriophage P22/physiology; Capsid/genetics; Capsid/metabolism; Capsid Proteins; Chromosome Mapping; Evolution, Molecular; Glutamic Acid/genetics; Glycine/genetics; Open Reading Frames; Phenotype; Protein Precursors/genetics; Protein Precursors/metabolism; Salmonella typhimurium/virology; Viral Structural Proteins/genetics; Viral Structural Proteins/metabolism; Virion; Virus Assembly
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
9CAUD:A0A0K2D089		GO:0046798: viral portal complex	ECO:0000316:	UniProtKB:ALA13170	C			complete CACAO 11460

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