Paratope
1. Antigen-binding fragment (Fab)
2. Antibody crystallizable region (Fc)
3. Heavy chains
4. Light chains
5. Variable region of the antibody. The paratope is the key-shaped section that makes direct contact with the antigen.[1]
6. Hinge regions
In immunology, a paratope, also known as an antigen-binding site, is the part of an antibody which recognizes and binds to an antigen.[1][2] It is a small region at the tip of the antibody's antigen-binding fragment and contains portions of the antibody's heavy chain and light chain.[1][2] Each paratope is a set of six complementarity-determining regions - three on the light chain and three on the heavy chain - that extend from a fold of anti-parallel beta sheets.[2] Each arm of the Y-shaped antibody has an identical paratope at the end.[2]
B-cell receptors include antibodies, so they include paratopes. All of the paratopes on any individual B cell are identical.[2] The uniqueness of a paratope allows it to bind to only one epitope with high affinity and, as a result, each B cell can only respond to one epitope. The binding of paratopes on B-cell receptors to their specific epitope is a critical step in the adaptive immune response.
Variability
[edit]The structure and properties of paratopes differ greatly among species. In jawed vertebrates, V(D)J recombination enables one individual to produce billions of different paratopes.[3][4] However, the number of possible paratopes is limited by the composition of the V, D, and J genes and the structure of the antibody.[3] In many species, additional mechanisms increase the diversity of possible paratopes. In cows, an extra-long complementarity-determining region is considered to have an essential role in diversifying paratopes.[3][5] Chickens and rabbits use gene conversion to increase the number of possible paratopes.[3]
References
[edit]- 1 2 3 Lefranc MP (2013). "Paratope". In Dubitzky W, Wolkenhauer O, Cho KH, Yokota H (eds.). Encyclopedia of Systems Biology. New York, NY: Springer. pp. 1632–1633. doi:10.1007/978-1-4419-9863-7_673. ISBN 978-1-4419-9863-7.
- 1 2 3 4 5 Punt J, Stranford SA, Jones PP, Owen JA (2019). Kuby immunology (Eighth ed.). New York. ISBN 978-1-4641-8978-4. OCLC 1002672752.
{{cite book}}: CS1 maint: location missing publisher (link) - 1 2 3 4 de los Rios M, Criscitiello MF, Smider VV (August 2015). "Structural and genetic diversity in antibody repertoires from diverse species". Current Opinion in Structural Biology. 33: 27–41. doi:10.1016/j.sbi.2015.06.002. PMC 7039331. PMID 26188469.
- ↑ Litman GW, Rast JP, Fugmann SD (August 2010). "The origins of vertebrate adaptive immunity". Nature Reviews. Immunology. 10 (8): 543–53. doi:10.1038/nri2807. PMC 2919748. PMID 20651744.
- ↑ Wang F, Ekiert DC, Ahmad I, Yu W, Zhang Y, Bazirgan O, et al. (June 2013). "Reshaping antibody diversity". Cell. 153 (6): 1379–93. doi:10.1016/j.cell.2013.04.049. PMC 4007204. PMID 23746848.
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