Structural highlights
Function[PORTL_BPP22] Required for successful condensation of DNA within the capsid. Gp1 is a minor structural protein. The portal protein is present as a single ring-shaped dodecamer located at the point where tails attach. It is through this ring that DNA is thought to enter the prohead. [VG04_BPP22] Together with gp10 and gp26, gp4 is required for stabilization of the condensed DNA within the capsid; perhaps by plugging the hole through which the DNA enters. Publication Abstract from PubMedDNA viruses such as bacteriophages and herpesviruses deliver their genome into and out of the capsid through large proteinaceous assemblies, known as portal proteins. Here, we report two snapshots of the dodecameric portal protein of bacteriophage P22. The 3.25-A-resolution structure of the portal-protein core bound to 12 copies of gene product 4 (gp4) reveals a ~1.1-MDa assembly formed by 24 proteins. Unexpectedly, a lower-resolution structure of the full-length portal protein unveils the unique topology of the C-terminal domain, which forms a ~200-A-long alpha-helical barrel. This domain inserts deeply into the virion and is highly conserved in the Podoviridae family. We propose that the barrel domain facilitates genome spooling onto the interior surface of the capsid during genome packaging and, in analogy to a rifle barrel, increases the accuracy of genome ejection into the host cell. Three-dimensional structure of a viral genome-delivery portal vertex.,Olia AS, Prevelige PE Jr, Johnson JE, Cingolani G Nat Struct Mol Biol. 2011 May;18(5):597-603. Epub 2011 Apr 17. PMID:21499245[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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