names in breadcrumbs
Picornavirales is an order of viruses with vertebrate, insect, algal or 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 families within this order share a number of common features:
The evolution of picorna-like viruses seems to have antedated the separation of eukaryotes into the extant crown groups.[3]
The taxonomy of this group has been reorganized by the International Committee on Taxonomy of Viruses in its 9th report in 2011.[4] The order contains six families and two unassigned genera. Although they did show some similarities, the families Caliciviridae and Potyviridae have not been included in the order, because they differed in some key features (capsid symmetry, absence of conservation in the sequence module, etc.).
Picornavirales is an order of viruses with vertebrate, insect, algal or plant hosts. The name has a dual etymology. First, picorna- is an acronym for poliovirus, insensitivity to ether, coxsackievirus, orphan virus, rhinovirus, and ribonucleic acid. Secondly, pico-, meaning extremely small, combines with RNA to describe these very small RNA viruses.
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, VPg, covalently attached to its 5' end, and usually a poly-adenylated 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 Proteinase 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 PicornaviralesThe evolution of picorna-like viruses seems to have antedated the separation of eukaryotes into the extant crown groups.
