Peplomer

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As peplomer (from Greek πέπλος peplos "garment ceiling") is referred to outwardly projecting protein structures in a virus envelope , which at a electron-microscopic visible image. They have a role in binding to the host cell .

The term is only rarely used today and is no longer used for all envelope proteins that protrude outwards; it is mostly replaced by the less precise expression “ spikes ” ( English for “thorn, sting”). However, this suggests a pointed structure, which is not the case with the envelope structures mentioned; they are round, flattened or button-shaped on the outside. Both terms, peplomer and spikes, 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.

Peplomers are made up of viral membrane proteins that are anchored in the lipid membrane with a protein domain ( transmembrane domain ). Another domain protrudes outwards and is usually glycosylated through the attachment of various sugar residues . This outer domain of the peplomer mediates the binding to the surface receptors of the target cell and thus the entry of the virus into the cell. The outer epitopes of the peplomeres also define the serological properties of the virus and the interaction with the host's antibodies . A peplomer can be composed of individual membrane proteins or membrane proteins which have been assembled to form dimers or trimers , and the subunits can be identical ( homomer ) or different ( heteromer ). The composition of a peplomer (from the so-called “spike proteins”) can be presented in a formalized way, for example a simple homodimer from two different envelope proteins E1 and E2 is written as [E1, E2], these dimers in turn combine to form larger groups, e.g. . B. trimers, this is formalized: [E1, E2] 3 . A peplomer with the formula [E1, E2, E3] 2 would represent two trimmers made of three different envelope proteins that together form a hexamer .

Today the term peplomer is mostly only used for a few virus groups in which the envelope proteins develop particularly large and characteristic structures, for example in the Orthomyxoviridae and the Coronaviridae .

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  • F. Fenner et al .: The Biology of Animal Viruses, 2nd edition, New York, London 1968, ISBN 0-12-253040-3 , pp. 5f
  • DJ Garwes et al .: Identification of epitopes of immunological importance on the peplomer of porcine transmissible gastroenteritis virus . Adv Exp Med Biol. (1987) 218: pp. 509-515, PMID 2449047
  • HG 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): pp. 253-263, PMID 2429473