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An RNA virus is a virus—other than a retrovirus—that has ribonucleic acid (RNA) as its genetic material. The nucleic acid is usually single-stranded RNA (ssRNA) but it may be double-stranded (dsRNA). Notable human diseases caused by RNA viruses include the common cold, influenza, SARS, MERS, Covid-19, Dengue Virus, hepatitis C, hepatitis E, West Nile fever, Ebola virus disease, rabies, polio, mumps, and measles.
The hepatitis C virus (HCV) is a small, enveloped, positive-sense single-stranded RNA virus of the family Flaviviridae. The hepatitis C virus is the cause of hepatitis C and some cancers such as liver cancer and lymphomas in humans.
A viral protein is both a component and a product of a virus. Viral proteins are grouped according to their functions, and groups of viral proteins include structural proteins, nonstructural proteins, regulatory proteins, and accessory proteins. Viruses are non-living and do not have the means to reproduce on their own, instead depending on their host cell's resources in order to reproduce. Thus, viruses do not code for many of their own viral proteins, and instead use the host cell's machinery to produce the viral proteins they require for replication.
Brome mosaic virus (BMV) is a small, positive-stranded, icosahedral RNA plant virus belonging to the genus Bromovirus, family Bromoviridae, in the Alphavirus-like superfamily.
A catalytic triad is a set of three coordinated amino acids that can be found in the active site of some enzymes. Catalytic triads are most commonly found in hydrolase and transferase enzymes. An acid-base-nucleophile triad is a common motif for generating a nucleophilic residue for covalent catalysis. The residues form a charge-relay network to polarise and activate the nucleophile, which attacks the substrate, forming a covalent intermediate which is then hydrolysed to release the product and regenerate free enzyme. The nucleophile is most commonly a serine or cysteine amino acid, but occasionally threonine or even selenocysteine. The 3D structure of the enzyme brings together the triad residues in a precise orientation, even though they may be far apart in the sequence.
Alphavirus is a genus of RNA viruses, the sole genus in the Togaviridae family. Alphaviruses belong to group IV of the Baltimore classification of viruses, with a positive-sense, single-stranded RNA genome. There are 32 alphaviruses, which infect various vertebrates such as humans, rodents, fish, birds, and larger mammals such as horses, as well as invertebrates. Alphaviruses that could infect both vertebrates and arthropods are referred dual-host alphaviruses, while insect-specific alphaviruses such as Eilat virus and Yada yada virus are restricted to their competent arthropod vector. Transmission between species and individuals occurs mainly via mosquitoes, making the alphaviruses a member of the collection of arboviruses – or arthropod-borne viruses. Alphavirus particles are enveloped, have a 70 nm diameter, tend to be spherical, and have a 40 nm isometric nucleocapsid.
Cysteine proteases, also known as thiol proteases, are hydrolase enzymes that degrade proteins. These proteases share a common catalytic mechanism that involves a nucleophilic cysteine thiol in a catalytic triad or dyad.
Heparan sulfate (HS) is a linear polysaccharide found in all animal tissues. It occurs as a proteoglycan in which two or three HS chains are attached in close proximity to cell surface or extracellular matrix proteins. It is in this form that HS binds to a variety of protein ligands, including Wnt, and regulates a wide range of biological activities, including developmental processes, angiogenesis, blood coagulation, abolishing detachment activity by GrB, and tumour metastasis. HS has also been shown to serve as cellular receptor for a number of viruses, including the respiratory syncytial virus. One study suggests that cellular heparan sulfate has a role in SARS-CoV-2 Infection, particularly when the virus attaches with ACE2.
In molecular biology Proteinase K is a broad-spectrum serine protease. The enzyme was discovered in 1974 in extracts of the fungus Engyodontium album. Proteinase K is able to digest hair (keratin), hence, the name "Proteinase K". The predominant site of cleavage is the peptide bond adjacent to the carboxyl group of aliphatic and aromatic amino acids with blocked alpha amino groups. It is commonly used for its broad specificity. This enzyme belongs to Peptidase family S8 (subtilisin). The molecular weight of Proteinase K is 28,900 daltons.
Ubiquitin-like modifier-activating enzyme 7 is a protein that in humans is encoded by the UBA7 gene.
NS2-3 protease is an enzyme responsible for proteolytic cleavage between NS2 and NS3, which are non-structural proteins that form part of the HCV virus particle. NS3 protease of hepatitis C virus, on the other hand, is responsible for the cleavage of non-structural protein downstream. Both of these proteases are directly involved in HCV genome replication, that is, during the viral life-cycle that leads to virus multiplication in the host that has been infected by the virus.
Nonstructural protein 2 (NS2) is a viral protein found in the hepatitis C virus. It is also produced by influenza viruses, and is alternatively known as the nuclear export protein (NEP).
Mayaro virus disease is a mosquito-borne zoonotic pathogen endemic to certain humid forests of tropical South America. Infection with Mayaro virus causes an acute, self-limited dengue-like illness of 3–5 days' duration. The causative virus, abbreviated MAYV, is in the family Togaviridae, and genus Alphavirus. It is closely related to other alphaviruses that produce a dengue-like illness accompanied by long-lasting arthralgia. It is only known to circulate in tropical South America.
Oryzin is an enzyme. This enzyme catalyses the following chemical reaction
Flavivirin is an enzyme.
Hepacivirin is an enzyme. This enzyme catalyses the following chemical reaction:
Pestivirus NS3 polyprotein peptidase is an enzyme. This enzyme catalyses the following chemical reaction
Saccharopepsin is an enzyme. This enzyme catalyses the following chemical reaction
Bacillolysin is an enzyme. This enzyme catalyses the following chemical reaction
The PA clan is the largest group of proteases with common ancestry as identified by structural homology. Members have a chymotrypsin-like fold and similar proteolysis mechanisms but can have identity of <10%. The clan contains both cysteine and serine proteases. PA clan proteases can be found in plants, animals, fungi, eubacteria, archaea and viruses.
References
- ↑ Kräusslich HG, Wimmer E (1988). "Viral proteinases". Annual Review of Biochemistry. 57: 701–54. doi:10.1146/annurev.bi.57.070188.003413. PMID 3052288.
- ↑ Strauss EG, De Groot RJ, Levinson R, Strauss JH (December 1992). "Identification of the active site residues in the nsP2 proteinase of Sindbis virus". Virology. 191 (2): 932–40. doi:10.1016/0042-6822(92)90268-t. PMC 7131396 . PMID 1448929.
- ↑ Tong L, Wengler G, Rossmann MG (March 1993). "Refined structure of Sindbis virus core protein and comparison with other chymotrypsin-like serine proteinase structures". Journal of Molecular Biology. 230 (1): 228–47. doi:10.1006/jmbi.1993.1139. PMID 8450538.
