Commentary - Virology Research Journal (2021) Virology Research Journal (Special Issue 3-2021)
Structural examination of viral-coded proteins.
Department of Virology, Iuliu Hatieganu University of Medicine and Pharmacy, Cluj-Napoca, Romania
- Corresponding Author:
- Dr. Christa Martin
Department of Virology
Iuliu Hatieganu University
Accepted date:15 September, 2021
Citation:Martin C.Structural examination of viral -coaded protiens. Virol Res J 2021;5(S3):3.
Some virus-coded proteins are structural, that is, they're wont to construct the capsid, envelope, and other components of the virion. Other proteins are non-structural; these aren't present within the virion but are involved in various viral replication processes including virion assembly. Many non-structural proteins are enzymes, which can be involved in macromolecule replication, transcription, and translation, also because the shutdown of host cell functions, the inhibition of innate immunity, and therefore the subversion of cellular machinery to viral synthetic activities. There are various sorts of replicases (also called polymerases; e.g., DNA-dependent DNA replicase or polymerase) and other enzymes involved in viral macromolecule replication, transcriptases that transcribe mRNA from viral DNA or RNA genomes, and various proteases, helicases, and ligases. Reverse transcriptase, an enzyme that transcribes DNA from an RNA template, is found uniquely in retroviruses and hepadnaviruses. Others enzymes found only in retroviruses are involved in the integration of the DNA product of reverse transcription into cellular chromosomal DNA. Poxviruses, which replicate within the cytoplasm and thus have less access to cellular machinery, duplicate variety of host enzymes that function in processing RNA transcripts and replicating the DNA genome.
The capsid is made from identical non-covalently linked structural subunits, which can be discernible by microscopy as protrusions or depressions on the surface of virions. These may correspond to individual viral proteins or aggregates of proteins. Only virions are assembled from the first products of protein synthesis; that's individual polypeptides; in most cases virion capsids are constructed from distinct assembly units "capsomeres" of several components, themselves often derived by modification or cleavage of precursors. Each subassembly may contain quite one polypeptide. One crucial step in virion assembly is that the incorporation of the viral macromolecule into the nascent virion several different mechanisms driving this process are recognized including the presence of packaging signals within the macromolecule sequence of the genome.
Viral Envelope contains Lipids and in most cases the integrity of the envelope is important for viral infectivity. The envelope is acquired when the nucleocapsid is extruded through one among the cellular membrane. This process isn't limited to the outer cell membrane: many viruses mature on internal, cytoplasmic membranes or maybe bud through the host nuclear membrane. The lipids of the viral envelope are derived directly from the cellular membrane, but the main proteins related to the envelope are virus-coded. Most lipids found in enveloped viruses are constructed into a typical lipid bilayer, during which the virus-coded glycoprotein peplomers and in some cases other viral proteins are embedded. As a consequence, the composition of the lipids of particular viruses differs consistent with the composition of the membrane lipids of the host cells during which replication takes place. The composition of the membrane lipids of viruses also varies with the actual membrane system employed for virion budding. For example, the lipids of paramyxoviruses which bud from the cell wall of host cells differ from those of bunyaviruses and coronaviruses that cause through the membranes of intracytoplasmic organelles. Lipids constitute about 20% to 35% of the dry weight of most enveloped viruses; some 50% to 60% of viral envelope lipid is phospholipid and most of the rest consists of cholesterol.