Togaviridae

The Togaviridae family ( togaviruses ) currently includes two genera of enveloped viruses (Latin toga: Coat ) with a single-stranded RNA of positive polarity. The Togaviridae belong to the genus Alphavirus important types of virus that is transmitted by insect-borne diseases to humans and animals as well as in the monotypic genus Rubivirus the causative agent of rubella.

Morphology

The spherical virus particles of the Togaviridae are about 70 nm in size in diameter and of a lipid membrane ( viral envelope ) surrounding it. In the envelope as distinct spikes heterodimers in both the viral envelope proteins are incorporated E1 and E2 ( 45-58 kDa). Within the genus Alphavirus, the heterodimers store together to form 80 and form a trimer (otherwise occurring only in capsids ) icosahedral shell structure. Some alphaviruses nor can a third envelope protein E3 ( 10 kDa) are emerging. Very closely attached to the envelope can be found in the interior of an approximately 40 nm in diameter large capsid from 240 molecules of the core protein CP (30-33 kDa ) with an icosahedral symmetry (T = 4). The capsid of rubella virus consists of 180 homodimers of the core protein in an icosahedral symmetry (T = 3), and has no such close association to the viral envelope as alphaviruses; the rubella virus is therefore often variable in shape. The fixed ratio of coat proteins to capsid proteins (1:1 ) is particularly during the assembly of the capsids of alphaviruses important.

The genome of the Togaviridae consists of a single-stranded, linear RNA with positive polarity ( ( ) ssRNA ) and from 9.7 to 11.8 kb in size. Located at its 5 ' end, a 5' cap structure, followed by the sequence for the most four non-structural proteins ( nsP1 -4), the structural proteins (CP, E1, E2) and at the 3'end a poly ( A) tail. Thus, the genome serve as messenger RNA for translation.

Replication

Togaviruses attach to via specific receptors on the cell surface and are taken up by a ausbildendes to Endosombläschen. At neutral pH outside the cell, the E2 envelope protein covers the E1 protein. Inside the endosome, the outer domain of the E1 protein are now exposed at an acidic pH, containing a fusion sequence and induce the fusion of the viral envelope and endosome. So that the capsid is released into the cytosol, is divided, and outputs the genome free. The ( ) ssRNA serves initially only the translation of the nonstructural proteins are synthesized as a large polyprotein and cleaved by cellular signal peptidases thereof. The sequences for the structural proteins are, however, only a complementary - ssRNA copied as a template by the viral RNA polymerase ( replicase ) and translated as separate short (mRNA ). This short ( subgenomic ) mRNA is additionally packed with the rubella virus in the virion. After the synthesis of new genomic RNA and the viral structural proteins, the transport of glycosylated envelope proteins from the endoplasmic reticulum (ER ) via the Golgi apparatus to the cell membrane begins. Here, finally, is the assembly of envelope and capsid and budding ( budding ) instead of new virions. In alphaviruses, the capsid of the RNA is already formed before, during rubella virus capsid formation begins with the deposition predominantly in the membrane of the ER instead of the happening and the budding of rubella virus.

System

  • Family Togaviridae Genus Alphavirus Species Aura virus
  • Species Barmah Forest virus
  • Species Bebaru virus
  • Species Cabassou virus
  • Species Chikungunya virus
  • Eastern equine encephalitis virus species
  • Species Everglades virus
  • Species Fort Morgan virus
  • Species Getah virus
  • Species Highlands J virus
  • Species Mayaro virus
  • Species Middleburg virus
  • Species Mosso - the - Pedras virus
  • Species Mucambo virus
  • Species Ndumu virus
  • Species O'nyong - nyong virus
  • Species Pixuna virus
  • Species Rio Negro Virus
  • Species, Ross River virus
  • Species Salmon pancreas disease virus
  • Species Semliki Forest virus
  • Species Sindbis virus
  • Species Southern elephant seal virus
  • Species Tonate virus
  • Species Trocara virus
  • Species Una virus
  • Venezuelan equine encephalitis virus species
  • Western equine encephalitis virus species
  • Species Whataroa virus
  • Genus Rubivirus species rubella

Non - classified species within the family:

  • Triniti virus
Virus classification National Center for Biotechnology Information Dimer (chemistry) RNA-Polymerase Virus#Etymology Ross-River-Virus
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