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Coronaviruses 004 lores.jpg
Transmission electron micrograph of Avian coronavirus
Illustration of a SARS-CoV-2 virion
Illustration of a SARS-CoV-2 virion[2]     Red: spike proteins (S)     Grey: lipid bilayer envelope     Yellow: envelope proteins (E)     Orange: membrane proteins (M)
Virus classification e
(unranked): Virus
Realm: incertae sedis
Kingdom: incertae sedis
Phylum: incertae sedis
Class: incertae sedis
Order: Nidovirales
Family: Coronaviridae
Subfamily: Orthocoronavirinae
  • Coronavirinae

Coronaviruses are a group of RNA viruses.[5][6] They cause diseases in birds and mammals, including humans. These diseases can be mild, or they can be fatal. In humans and birds, they cause respiratory tract infections. Mild illnesses in humans include some cases of the common cold (which is also caused by other viruses, for example rhinoviruses). More lethal varieties can cause SARS, MERS, and COVID-19.

They are enveloped viruses with a positive-sense RNA genome.[7] The genome size of coronaviruses is about 26 to 32 kilobases,[8] which is extraordinarily large for an RNA virus. There are four major groups of coronaviruses, called alpha, beta, gamma and delta.

The most famous coronavirus is one of the betas, the kind that causes Coronavirus disease 2019 in humans.

The name "coronavirus" comes from the Latin word corona, meaning "crown" or "halo", and refers to how virions look under an electron microscopy (E.M.).[9] They have a fringe of large, bulbous surface projections looking like a crown. This morphology is created by the viral spike (S) peplomers, which are proteins on the surface of the virus. They decide which cells the virus can infect.

Proteins of coronaviruses are the spike (S), envelope (E), membrane (M) and nucleocapsid (N).

Diseases[change | change source]

Coronaviruses infect the upper respiratory and gastrointestinal tracts of mammals and birds. Six different strains of coronaviruses infect humans. These include:

Coronaviruses are believed to cause many common colds in human adults. The significance and economic impact of coronaviruses is hard to assess. Unlike rhinoviruses (another common cold virus), human coronaviruses are easy to grow in the laboratory.

Structure[change | change source]

Structure of a coronavirus

Coronaviruses are large, spherical particles with unique surface projections.[10] Their size is variable, averageing 80 to 120 nms[11] The total molecular weight is on average 40,000 kDa. They are enclosed in an envelope studded with projecting protein molecules.[12] These layers protect the virus when it is outside the host cell.[13]

The viral envelope is made up of a lipid bilayer in which the membrane (M), envelope (E) and spike (S) structural proteins are anchored.[14] The ratio of E:S:M in the lipid bilayer is approximately 1:20:300.[15] The E and M protein are the structural proteins that combined with the lipid bilayer to shape the viral envelope and maintain its size. S proteins are needed for interaction with the host cells. But human coronavirus NL63 is peculiar in that its M protein has the binding site for the host cell, and not its S protein.[16] The diameter of the envelope is 85 nm.

Related pages[change | change source]

References[change | change source]

  1. "Virus Taxonomy: 2018b Release". International Committee on Taxonomy of Viruses (ICTV). March 2019. Archived from the original on 4 March 2018. Retrieved 24 January 2020.
  2. Giaimo C (1 April 2020). "The Spiky Blob Seen Around the World". The New York Times. Archived from the original on 2 April 2020. Retrieved 6 April 2020.
  3. "2017.012-015S" (xlsx). International Committee on Taxonomy of Viruses (ICTV). October 2018. Archived from the original on 14 May 2019. Retrieved 24 January 2020.
  4. "ICTV Taxonomy history: Orthocoronavirinae". International Committee on Taxonomy of Viruses (ICTV). Retrieved 24 January 2020.
  5. de Groot R.J. et al 2011. (2012). "Family Coronaviridae". Ninth Report of the International Committee on Taxonomy of Viruses. Elsevier, Oxford. pp. 806–828. ISBN 978-0-12-384684-6. Unknown parameter |editors= ignored (help)
  6. International Committee on Taxonomy of Viruses. "ICTV Master Species List 2009 – v10" (xls).
  7. enveloped = has viral envelopes covering their protective protein capsids; positive sense = the RNA sequence may be directly translated into the desired viral proteins.
  8. One kilobase = 1000 base pairs
  9. virion = complete virus particle.
  10. Goldsmith CS, Tatti KM, Ksiazek TG, Rollin PE, Comer JA, Lee WW, et al. (February 2004). "Ultrastructural characterization of SARS coronavirus". Emerging Infectious Diseases. 10 (2): 320–6. doi:10.3201/eid1002.030913. PMC 3322934. PMID 15030705. Virions acquired an envelope by budding into the cisternae and formed mostly spherical, sometimes pleomorphic, particles that averaged 78 nm in diameter (Figure 1A).
  11. Masters PS (2006). "The molecular biology of coronaviruses". Advances in Virus Research. 66: 193–292. doi:10.1016/S0065-3527(06)66005-3. ISBN 9780120398690. PMC 7112330. PMID 16877062.
  12. Lalchhandama K (2020). "The chronicles of coronaviruses: the electron microscope, the doughnut, and the spike". Science Vision. 20 (2): 78–92. doi:10.33493/scivis.20.02.03.
  13. Neuman BW, Kiss G, Kunding AH, Bhella D, Baksh MF, Connelly S, et al. (April 2011). "A structural analysis of M protein in coronavirus assembly and morphology". Journal of Structural Biology. 174 (1): 11–22. doi:10.1016/j.jsb.2010.11.021. PMC 4486061. PMID 21130884. See Figure 10.
  14. Lai MM, Cavanagh D (1997). "The molecular biology of coronaviruses". Advances in Virus Research. 48: 1–100. doi:10.1016/S0065-3527(08)60286-9. ISBN 9780120398485. PMC 7130985. PMID 9233431.
  15. Cavanagh D, Mawditt K, Sharma M, Drury SE, Ainsworth HL, Britton P, Gough RE (August 2001). Schmidt A, Weber O, Wolff MH (eds.). "Detection of a coronavirus from turkey poults in Europe genetically related to infectious bronchitis virus of chickens". Avian Pathology. Birkhäuser Advances in Infectious Diseases BAID. Birkhäuser. 30 (4): 355–68. doi:10.1007/3-7643-7339-3_1. ISBN 978-3-7643-7339-9. PMC 7123520. PMID 19184921.
  16. Naskalska A, Dabrowska A, Szczepanski A, Milewska A, Jasik KP, Pyrc K (October 2019). "Membrane Protein of Human Coronavirus NL63 Is Responsible for Interaction with the Adhesion Receptor". Journal of Virology. 93 (19). doi:10.1128/JVI.00355-19. PMC 6744225. PMID 31315999.