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17-406: Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera ( Alpha -, Beta- , Gamma- , and Delta- ) of coronaviruses . They are positive-sense , single-stranded RNA viruses that infect mammals , including humans . They have spherical virions with club-shaped surface projections formed by trimers of the spike protein , and a viral envelope . Alphacoronaviruses are in
34-506: A trimer ( PDB : 3jcl , 6acg ); its core structure resembles that of paramyxovirus F (fusion) proteins. The receptor usage is not very conserved; for example, among Sarbecovirus , only a sub-lineage containing SARS share the ACE2 receptor. The viruses of subgenera Embecovirus differ from all others in the genus in that they have an additional shorter (8 nm) spike-like protein called hemagglutinin esterase (HE) ( P15776 ). It
51-678: Is a subgenus of coronaviruses in the genus Betacoronavirus . The viruses in this subgenus, unlike other coronaviruses , have a hemagglutinin esterase (HE) gene. The viruses in the subgenus were previously known as group 2a coronaviruses . The viruses of this subgenus, like other coronaviruses, have a lipid bilayer envelope in which the membrane (M), envelope (E) and spike (S) structural proteins are anchored. Unlike other coronaviruses, viruses in this subgenus also have an additional shorter spike-like structural protein called hemagglutinin esterase (HE). Genetic recombination can occur when two or more viral genomes are present in
68-473: Is believed to have been acquired from influenza C virus . Coronaviruses have a large genome size that ranges from 26 to 32 kilobases. The overall structure of β-CoV genome is similar to that of other CoVs, with an ORF1ab replicase polyprotein ( rep , pp1ab ) preceding other elements. This polyprotein is cleaved into 16 nonstructural proteins (see UniProt annotation of SARS rep , P0C6X7 ). As of May 2013, GenBank has 46 published complete genomes of
85-498: Is derived from Ancient Greek βῆτα ( bē̂ta , "the second letter of the Greek alphabet "), and κορώνη (korṓnē, “garland, wreath”), meaning crown, which describes the appearance of the surface projections seen under electron microscopy that resemble a solar corona . This morphology is created by the viral spike (S) peplomers , which are proteins that populate the surface of the virus and determine host tropism . The order Nidovirales
102-455: Is derived from Ancient Greek ἄλφα ( álpha , "the first letter of the Greek alphabet "), and κορώνη (korṓnē, "garland, wreath"), meaning crown, which describes the appearance of the surface projections seen under electron microscopy that resemble a solar corona . The virion is enveloped and spherical measuring 120–160 nm in diameter and a core shell of about 65 nm. Glycoproteins and trimers form large surface projections which create
119-458: Is named for the Latin nidus , which means 'nest'. It refers to this order's production of a 3′-coterminal nested set of subgenomic mRNAs during infection. Several structures of the spike proteins have been resolved. The receptor binding domain in the alpha- and betacoronavirus spike protein is cataloged as InterPro : IPR018548 . The spike protein, a type 1 fusion machine , assembles into
136-533: The 5'-end of the genome encode the major non-structural proteins expressed as a fusion protein by ribosomal frameshift . These include regions with protease , helicase and RNA polymerase motifs. There are seven other genes downstream which encode structural proteins. These are expressed from a 3'-coterminal nested set of subgenomic mRNAs . Both types of Alphacoronavirus 1 , feline coronavirus (FCoV) and canine coronavirus (CCoV), are known to exist in two serotypes. Serotype II targets Aminopeptidase N , while
153-417: The appearance of solar corona. This genus, like other coronaviruses, has a spike protein with a type I fusion machine (S2) and a receptor-binding domain (S1). It assembles into a trimer. Unlike beta- and gammacoronaviruses, this protein is not cleaved into two halves. The genome is positive-sense , single-stranded RNA with a length of 27 to 29 kilobases and a 3'- polyA tail. Two large, overlapping ORFs at
170-896: The genus Betacoronavirus (Group 2 CoV), four subgenera or lineages (A, B, C, and D) have traditionally been recognized. The four lineages have also been named using Greek letters or numerically. A fifth subgenus, Hibecovirus , was added more recently. Member subgenera and species include: Betacoronavirus 1 China Rattus coronavirus HKU24 Human coronavirus HKU1 Murine coronavirus Myodes coronavirus 2JL14 Severe acute respiratory syndrome–related coronavirus (SARSr-CoV or SARS-CoV) Hedgehog coronavirus 1 Middle East respiratory syndrome-related coronavirus (MERS-CoV) Pipistrellus bat coronavirus HKU5 Tylonycteris bat coronavirus HKU4 Eidolon bat coronavirus C704 Rousettus bat coronavirus GCCDC1 Rousettus bat coronavirus HKU9 Bat Hp-betacoronavirus Zhejiang2013 Embecovirus Embecovirus
187-447: The order Nidovirales . The betacoronaviruses of the greatest clinical importance concerning humans are OC43 and HKU1 (which can cause the common cold ) of lineage A, SARS-CoV-1 and SARS-CoV-2 (the causes of SARS and COVID-19 respectively) of lineage B, and MERS-CoV (the cause of MERS ) of lineage C. MERS-CoV is the first betacoronavirus belonging to lineage C that is known to infect humans. The name "betacoronavirus"
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#1732898425067204-503: The receptor for Serotype I is unknown. The difference is due to a different spike protein. There is a common ancestor for FCoV and CCoV. This ancestor gradually evolved into FCoV I and CCoV I. An S protein from an unknown virus was recombined into the ancestor and gave rise to CCoV II. CCoV II once again recombined with FCoV to create FCoV II. CCoV II gradually evolved into TGEV. A spike deletion in TGEV creates PRCV. All these viruses are sorted into
221-410: The reservoir for the subgenus Embecovirus , while bats are the reservoir for the other subgenera. The coronavirus genera are each composed of varying viral lineages with the betacoronavirus genus containing four such lineages: A, B, C, D. In older literature, this genus is also known as "group 2 coronaviruses". The genus is in the subfamily Orthocoronavirinae in the family Coronaviridae , of
238-591: The subfamily Orthocoronavirinae of the family Coronaviridae . Both the Alpha - and Betacoronavirus lineages descend from the bat viral gene pool . Alphacoronaviruses were previously known as " phylogroup 1 coronaviruses". The Alphacoronavirus genus is very diverse, particularly in bats. Most bat originating strains haven't been successfully isolated and cultured in laboratory. Alphacoronaviruses infecting other mammal species have been much better studied, see List of Coronavirus live isolates . The name alphacoronavirus
255-444: The subgenus Tegacovirus . The following subgenera and species are recognized: Betacoronavirus See text Betacoronavirus (β-CoVs or Beta-CoVs) is one of four genera ( Alpha -, Beta- , Gamma- , and Delta- ) of coronaviruses . Member viruses are enveloped , positive-strand RNA viruses that infect mammals , including humans . The natural reservoir for betacoronaviruses are bats and rodents. Rodents are
272-475: The subgenus Embecovirus . Also the betacoronavirus, Human SARS-CoV , appears to have had a complex history of recombination between ancestral coronaviruses that were hosted in several different animal groups. Alpha- and betacoronaviruses mainly infect bats, but they also infect other species like humans , camels , and rodents . Betacoronaviruses that have caused epidemics in humans generally induce fever and respiratory symptoms. They include: Within
289-465: The α- (group 1), β- (group 2), γ- (group 3), and δ- (group 4) CoVs. Genetic recombination can occur when two or more viral genomes are present in the same host cell. The dromedary camel Beta-CoV HKU23 exhibits genetic diversity in the African camel population. Contributing to this diversity are several recombination events that had taken place in the past between closely related betacoronaviruses of
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