Picornavirales is an order of viruses with vertebrate, invertebrate, protist and plant hosts.[1] The name has a dual etymology.[2] First, picorna- is an acronym for poliovirus, insensitivity to ether, coxsackievirus, orphan virus, rhinovirus, and ribonucleic acid.[2] Secondly, 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.
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):
^Le Gall, Olivier; Christian, Peter; Fauquet, Claude M.; King, Andrew M. Q.; Knowles, Nick J.; Nakashima, Nobuhiko; Stanway, Glyn; Gorbalenya, Alexander E. (2008-04-01). "Picornavirales, a proposed order of positive-sense single-stranded RNA viruses with a pseudo-T = 3 virion architecture". Archives of Virology. 153 (4): 715–27. doi:10.1007/s00705-008-0041-x. PMID18293057. S2CID2303309.
^ abc"Picornaviridae". International Committee on Taxonomy of Viruses (ICTV). October 2017. Archived from the original on September 21, 2017. Retrieved 5 February 2019.
