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Tal­mu­dic Ques­tion #105

Do you know of any eu­kary­otic virus that has a tail, and, if not, why do you sup­pose there aren't any?

 

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Marco
12 years ago

There might be some evo­lu­tion­ary ad­van­tage to be­ing en­do­cy­tosed by the tar­get cell in­stead of re­quir­ing a tail to at­tach and in­ject ge­netic ma­te­r­ial. Per­haps as­sem­bly of vi­ral tails was an evo­lu­tion­ary pres­sure that drove the first eu­kary­otes to­wards spa­tial arrange­ment of tran­scrip­tion and trans­la­tion. Tails work for viruses like T7 phage be­cause tran­scrip­tion and trans­la­tion both oc­cur in the cy­tosol of prokary­otes. Sep­a­ra­tion of the two processes could have been a de­fense against vi­ral as­sem­bly.
Elio replies:
Nice point, Marco. Who knows, you my even be right!

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jeff
12 years ago

Would you con­sider the spike og Chlorellaviruses a "tail"? http://cryoem.ucsd.edu/publication-pdfs/2009-Cherrier-etal-PNAS.pdf
Merry com­ments: I imag­ine Elio had the canon­i­cal tails of the My­oviruses and Siphoviruses in mind here, in which case I'd say the spike does not qual­ify. Those tails are com­plex pro­tein struc­tures that are pre­assem­bled and then at­tached to the filled cap­sid where they later func­tion as a tube for genome de­liv­ery. Like those tails, the Chlorellavirus spike in­di­cates a unique ver­tex spe­cial­ized for host interaction—likely your point here. In­deed the pointed spike struc­ture may be in­volved in pen­e­tra­tion of the host. How­ever, the spike does not con­tain a chan­nel for genome de­liv­ery.
'Tail' is be­ing used to de­scribe nu­mer­ous struc­tures even among the phages that don't con­form to such a nar­row de­f­i­n­i­tion (e.g., the ex­ten­si­ble tail of Podophages such as T7, the pro­tein chute formed af­ter ad­sorp­tion by PRD1, and the pro­tein tube formed also af­ter ad­sorp­tion by phiX174). As usual, phage and virus va­ri­ety con­founds our ter­mi­nol­ogy.
BTW, there is a more re­cent pa­per also from the Ross­man lab show­ing that takes a close look at the Chlorellavirus spike struc­ture dur­ing in­fec­tion:
http://www.ncbi.nlm.nih.gov/pubmed/21873222

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