Picornavirales

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Picornavirales
Picornavirus replication cycle
Picornavirus replication cycle
Virus classification Edit this classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Pisuviricota
Class: Pisoniviricetes
Order: Picornavirales

Picornavirales is an order of

pico-, meaning extremely small, combines with RNA to describe these very small RNA viruses.[2]
The order comprises viruses that historically are referred to as picorna-like viruses.

Characteristics

The families within this order share a number of common features:

  • The virions are non-enveloped, icosahedral, and about 30 nanometers in diameter.
  • The capsid has a "pseudo T=3" structure, and is composed of 60 protomers each made of three similar-sized but nonidentical beta barrels.
  • The genome is made of one or a few single-stranded RNA(s) serving directly as mRNA, without overlapping open reading frames.
  • The genome has a small protein,
    3' end
    .
  • Each genome RNA is translated into
    polyprotein
    (s) yielding mature viral proteins through one or several virus-encoded proteinase(s).
  • A hallmark of the Picornavirales is a conserved module of sequence domains, Hel-Pro-Pol, which is typical of (from the amino- to the carboxy-end of the polyprotein):
    • A helicase belonging to superfamily III
    • [the VPg is encoded between these two domains]
    • A chymotrypsin-like protease where the catalytic residue is typically a cysteine rather than a serine,
    • A polymerase belonging to superfamily I; this conserved module is a hallmark of the Picornavirales

The evolution of picorna-like viruses seems to have antedated the separation of eukaryotes into the extant crown groups.[3]

Taxonomy

Phylogenetic tree of representative viruses from order Picornavirales

The following families are recognized:[4]

References

  1. S2CID 2303309
    .
  2. ^ a b c "Picornaviridae". International Committee on Taxonomy of Viruses (ICTV). October 2017. Archived from the original on September 21, 2017. Retrieved 5 February 2019.
  3. S2CID 205497478
    .
  4. ^ "Virus Taxonomy: 2019 Release". talk.ictvonline.org. International Committee on Taxonomy of Viruses. Retrieved 30 April 2020.

External links

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