Spike protein

The peplomers (red and orange) of a SARS-CoV-2, the virus that causes COVID-19.

File:Novel Coronavirus SARS-CoV-2 Spike Protein (49583626473).jpg

3D print of one of the peplomers of SARS-CoV-2

Spike proteins, also known as peplomers (Greek: peplos 'robe', '[woman's] dress' + meros 'part'), are the knoblike structures generally composed of glycoproteins, projecting from the lipid bilayer of the surface of an enveloped virus. Peplomers play important roles in the infection process; they are responsible for the attachment of the virus particle or virion to receptor sites on the host cell's surface, and bringing about the release of the nucleocapsid containing the virus's genetic material into the host cell's cytoplasm by triggering fusion between the envelope and host membranes. They may have hemagglutinating activity or have enzyme activity such as neuraminidase. They are surface antigens.

The term peplomer is rarely used today and is no longer used for all outwardly protruding envelope proteins; it is mostly replaced by the less precise expression spike. However, this suggests a pointed structure, which is not the case with these envelope structures; they are round, flattened or button-shaped on the outside. Both terms, peplomer and spike, however, only describe a morphologically visible structure and are not identical to the expression membrane protein or coat protein; many other membrane proteins in viruses do not form these prominent structures.

Virus types

Peplomers can be seen in electron micrographs on the surface of enveloped viruses such as Orthomyxoviruses, Paramyxoviruses, Rhabdoviruses, Filoviruses, Coronaviruses, Bunyaviruses, Arenaviruses, and Retroviruses.

The tail fibers of some bacteriophages, especially the T4-like phages, are modified peplomers.

Influenza virus has two kinds of peplomers:

1. Cylinder shaped "haemagglutinin"
2. Mushroom-shaped "neuraminidase".

Antivirals

Bamlanivimab/etesevimab is a mix of two types of monoclonal antibody that target the surface spike protein of SARS-CoV-2.

Society and culture

Further information: COVID-19 misinformation

During the COVID-19 pandemic, anti-vaccination misinformation circulated on social media saying that spike proteins were dangerously "cytotoxic" and that mRNA vaccines containing them were therefore in themselves dangerous.

See also

• Viral entry
• Viral life cycle
• Types
• Signal peptide

Further reading

• F. Fenner et al.: The Biology of Animal Viruses, 2. Auflage, New York, London 1968, ISBN 0-12-253040-3, S. 5f
• D. J. Garwes et al.: Identification of epitopes of immunological importance on the peplomer of porcine transmissible gastroenteritis virus. Adv Exp Med Biol. (1987) 218: S. 509–515,
• H. G. Niesters et al.: The peplomer protein sequence of the M41 strain of coronavirus IBV and its comparison with Beaudette strains. Virus Res. (1986) 5(2-3): S. 253–263,