Coronaviridae

The virus family Coronaviridae is a family within the order Nidovirales. Their representatives cause very different diseases in different vertebrates such as mammals, rodents, fish and birds. Corona viruses are genetically highly variable and individual virus species can also infect several host species by overcoming the species barrier. The causative agent of SARS pandemic 2002/2003 - - Such Artübertritte among other infections with the SARS -associated coronavirus ( SARS -CoV ) in humans as well as the 2012 neuaufgetretenen Middle East respiratory syndrome coronavirus ( MERS -CoV ) emerged. In humans, particularly the Humane coronavirus species as the causative agent of mild respiratory infections ( colds ) to the severe acute respiratory syndrome is important.

With genome lengths of more than 30,000 nucleotides, the Coronaviridae are among the RNA viruses with the largest genomes known. The high genetic instability of viral RNA from approximately 10,000 nucleotides in length is achieved inter alia through a proofreading function of the viral RNA polymerase at the Coronaviridae.

Morphology

The 120 to 160 -nm virions possess a viral envelope, in 3 or 4 different membrane proteins are incorporated: A large, glycosylated S protein ( 180 to 220 kDa) is a trimer, with its lobe-shaped, about 20 nm outwardly extending spikes ( Peplomere ) the characteristic ring - shaped appearance of coronaviruses (Latin corona: wreath, crown). In lesser amounts of a second membrane protein E ( 9-12 kDa) and in addition only when the Human coronavirus OC43 and the coronavirus group 2, the HE protein ( hemagglutinin -esterase protein, 65 kDa). Which is also anchored in the sheath M protein ( 23 to 35 kDa), is directed inward and holds the inner side of the viral envelope (matrix protein).

Inside there is a probably icosahedral capsid, which in turn contains a helical nucleoprotein. This consists of the N nucleoprotein (50 to 60 kDa ), which is complexed to a strand of single-stranded RNA of positive polarity. Certain amino acid residues, projecting outwardly of the N protein to interact with the matrix protein M, such that the capsid is associated with the membrane interior.

Genome

The single-stranded RNA genome of the coronavirus is about 27,600 to 31,000 nucleotides ( nt) long, which coronaviruses have the longest of all known genomes of RNA viruses. At the 5 ' end there is a 5' cap structure and a non-coding region (UTR, untranslated region ) of about 200 to 400 nt, comprising a 65 to 98 nt short, so-called leader sequence. At the 3'- end of a further UTR of 200 to 500 nt adds, terminating in a poly (A ) tail. The genome of coronaviruses containing 6 to 14 open reading frames (ORFs ) of which the two largest ( the genes for the non-structural proteins 1 a and 1 b ) are located close to the 5 'end and overlap somewhat with different reading frames. The overlapping area forms a hairpin structure comprising a frameshifting during translation on the ribosomes in 20 to 30 % of the read cycles permits and thus leads to the synthesis of low amounts of the 1b protein.

System

The Coronaviridae family is divided on the basis of phylogenetic properties and host range of the species in two subfamilies and the genera alpha, beta and gamma (formerly Group 1, 2 and 3 of the old genus Coronavirus ) and Delta coronavirus and Toro virus and Bafinovirus. Indicated are only the most important species:

  • Family Coronaviridae
  • Subfamily Coronavirinae
  • Alphavirus genus Coronavirus
  • Species Canines coronavirus ( CCoV )
  • Species feline coronavirus (FCoV )
  • Species Human coronavirus 229E ( HCoV - 229E )
  • Species Porcine epidemic diarrhea virus ( PEDV )
  • Species Transmissible gastroenteritis virus ( TGEV )
  • Genus Beta coronavirus
  • Species Bovine coronavirus ( BCOV )
  • Species Human coronavirus OC43 ( HCoV - OC43 )
  • Species Human Enteric Coronavirus ( HECoV )
  • Species Murine Hepatitis Virus ( MHV )
  • Porcine hemagglutinating encephalomyelitis virus species (HEV )
  • Species Puffinosis coronavirus ( PCoV )
  • Species rat coronavirus ( RtCoV )
  • Species SARS coronavirus (SARS -CoV )
  • Species Middle East respiratory syndrome coronavirus ( MERS -CoV )
  • Gamma genus Coronavirus
  • Species Infectious Bronchitis Virus ( IBV)
  • Species turkey coronavirus ( TCoV )
  • Species pheasant coronavirus ( PhCoV )
  • Delta genus Coronavirus
  • Species bronze male coronavirus HKU13
  • Species throttle coronavirus HKU12
  • Subfamily Torovirinae
  • Genus torovirus
  • Genus Bafinivirus
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