![]() ![]() Spikes or peplomers can be visible in electron micrograph images of enveloped viruses such as orthomyxoviruses, paramyxoviruses, rhabdoviruses, filoviruses, coronaviruses, bunyaviruses, arenaviruses, and retroviruses. Being exposed on the surface of the virion, spike proteins can be antigens. : 33 Many spike proteins are membrane fusion proteins. : 329 The binding site for the cell-surface receptor is usually located at the tip of the spike. : 362 For example, influenza virus has two surface proteins with these two functions, hemagglutinin and neuraminidase. They may interact with cell-surface receptors located on the host cell and may have hemagglutinizing activity as a result, or in other cases they may be enzymes. ![]() ![]() Spikes typically have a role in viral entry. : 51–2 They are usually glycoproteins, more commonly via N-linked than O-linked glycosylation. They may also form protein–protein interactions with other viral proteins, such as those forming the nucleocapsid. Spike proteins are membrane proteins with typically large external ectodomains, a single transmembrane domain that anchors the protein in the viral envelope, and a short tail in the interior of the virion. Spikes or peplomers are usually rod- or club-shaped projections from the viral surface. More recently, the term "peplos" is considered a synonym for viral envelope. Early systems of viral taxonomy, such as the Lwoff- Horne- Tournier system proposed in the 1960s, used the appearance and morphology of the "peplos" and peplomers as important characteristics for classification. The term is derived from the Greek peplos, "a loose outer garment", "robe or cloak", or "woman mantle". The term "peplomer" refers to an individual spike from the viral surface collectively the layer of material at the outer surface of the virion has been referred to as the "peplos". : 29–33 The proteins are usually glycoproteins that form dimers or trimers. In virology, a spike protein or peplomer protein is a protein that forms a large structure known as a spike or peplomer projecting from the surface of an enveloped virus. Let me know if this type of explanation is useful, and if you would like me to continue.3D print of one of the trimeric spikes of SARS-CoV-2 This way it will be easier to understand the meaning of the swine flu virus sequences that were released this week. Tomorrow I’ll show you how each RNA codes for protein. This week, when we discussed the nucleotide sequence of swine influenza RNAs, we were referring to these RNA molecules. The interior of the virion also contains another protein called NEP. These RNA segments are the genes of influenza virus. Each RNA segment, as they are called, consists of RNA joined with several proteins shown in the diagram: B1, PB2, PA, NP. These are the genetic material of the virus they code for one or two proteins. Within the interior of the virion are the viral RNAs – 8 of them for influenza A viruses. This protein, which forms a shell, gives strength and rigidity to the lipid envelope. Also embedded in the lipid membrane is the M2 protein, which is the target of the antiviral adamantanes – amantadine and rimantadine.īeneath the lipid membrane is a viral protein called M1, or matrix protein. The NA protein is the target of the antiviral drugs Relenza and Tamiflu. The HA and NA are important in the immune response against the virus antibodies (proteins made by us to combat infection) against these spikes may protect against infection. We’ll discuss later how the HA and NA are given subtype numbers. ![]() These are the proteins that determine the subtype of influenza virus (A/H1N1, for example). Inserted into the lipid membrane are ‘spikes’, which are proteins – actually glycoproteins, because they consist of protein linked to sugars – known as HA (hemagglutinin) and NA (neuraminidase). It is an enveloped virus – that is, the outer layer is a lipid membrane which is taken from the host cell in which the virus multiplies. The influenza virion (as the infectious particle is called) is roughly spherical. Today we’ll start with the basic structure of influenza virus, illustrated above. I thought it might be useful to explain how the virus multiplies, how it infects us, and how we combat infection. In this week’s discussion of swine flu A/Mexico/09 (H1N1), we have considered many aspects of influenza virus biology that might not be familiar to some readers of virology blog. ![]()
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