Genome Gating in Tailed Bacteriophage Capsids

Unité de Virologie Moléculaire et Structurale, Gif-sur-Yvette, France.
Advances in Experimental Medicine and Biology (Impact Factor: 1.96). 01/2012; 726:585-600. DOI: 10.1007/978-1-4614-0980-9_25
Source: PubMed


Tailed bacteriophages use a portal system for genome entry and exit from viral capsids. Here, we review the mechanisms how these movements are controlled by the genome gatekeeper that assembles at the portal structure. Phage DNA is packaged at high pressure inside the viral capsid by a powerful motor. The viral genome is translocated through the central channel of the portal protein found at a single vertex of the capsid. Packaging is normally terminated by endonucleolytic cleavage of the substrate DNA followed by disassembly of the packaging motor and closure of the portal system, preventing leakage of the viral genome. This can be achieved either by conformational changes in the portal protein or by sequential addition of proteins that extend the portal channel (adaptors) and physically close it preventing DNA exit (stoppers). The resulting connector structure provides the interface for assembly of short tails (podoviruses) or for attachment of preformed long tails (siphoviruses and myoviruses). The connector maintains the viral DNA correctly positioned for ejection that is triggered by interaction of the phage particle with bacterial receptors. Recent exciting advances are providing new molecular insights on the mechanisms that ensure precise coordination of these critical steps required both for stable viral genome packaging and for its efficient release to initiate infection.

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Available from: E.V. Orlova, Oct 16, 2015
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    • "packaging. In many bacteriophages the DNA packaging depends on their portal structure (Johnson and Chiu, 2007; Tavares et al., 2012). In the future it would be interesting to study the structure of the portal vertices of EL, and compare it to the ones of phiKZ, and other related phages. "
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    • "A switch back to nuclease activity in response to the level of DNA filling of the capsid achieves the dsDNA termination cut ending the packaging cycle. This cleavage is either sequence-specific or sequence-independent (headful packaging mechanism) depending on the viral system (7). "
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