Biology:Immunophilins
In molecular biology, immunophilins are endogenous cytosolic peptidyl-prolyl isomerases (PPI) that catalyze the interconversion between the cis and trans isomers of peptide bonds containing the amino acid proline (Pro). They are chaperone molecules that generally assist in the proper folding of diverse "client" proteins. Immunophilins are traditionally classified into two families that differ in sequence and biochemical characteristics. These two families are: "cyclosporin-binding cyclophilins (CyPs)" and "FK506-binding proteins (FKBPs)".[1] In 2005, a group of dual-family immunophilins (DFI) has been discovered, mostly in unicellular organisms; these DFIs are natural chimera of CyP and FKBPs, fused in either order (CyP-FKBP or FKBP-CyP).[2]
Immunophilins act as receptors for immunosuppressive drugs such as sirolimus (rapamycin), cyclosporin (such as CsA) and tacrolimus (FK506), which inhibit the prolyl isomerase activity of the immunophilins. The drug-immunophilin complexes (CsA-CyP and FK506-FKBP) bind to calcineurin, which inhibits the phosphatase activity of calcineurin and engenders the immunosuppressive effects.[3] CsA and FK506 thus affect the calcium-dependent step of T cell response which prevents release of interleukin-2. Immunophilins also form protein complex with ryanodine and inositol triphosphate (IP3) which impacts the release of calcium.
FK506 binds with high affinity to other smaller proteins, such as FKBP-12. FKBP-12 and cyclophilins both share common peptide-prolyl isomerase activity. While the majority of the Peptide bonds within proteins exist in trans (planar) conformation because of the partial double-bond nature of the peptide bond,[4] a small fraction occurs in cis. Unlike regular peptide bonds, the X-Pro peptide bond does not adopt the intended trans conformation spontaneously, thus, cis-trans isomerization can be the rate-limiting (slowest) step in the process of protein folding.[5] Immunophilins, with their prolyl isomerase activity, thus function as protein-folding chaperones.
See also
References
- ↑ Barik, S. (December 2006). "Immunophilins: for the love of proteins". Cellular and Molecular Life Sciences 63 (24): 2889–2900. doi:10.1007/s00018-006-6215-3. ISSN 1420-682X. PMID 17075696.
- ↑ Adams, Brian; Musiyenko, Alla; Kumar, Rajinder; Barik, Sailen (2005-07-01). "A novel class of dual-family immunophilins". The Journal of Biological Chemistry 280 (26): 24308–24314. doi:10.1074/jbc.M500990200. ISSN 0021-9258. PMID 15845546.
- ↑ Ho, S.; Clipstone, N.; Timmermann, L.; Northrop, J.; Graef, I.; Fiorentino, D.; Nourse, J.; Crabtree, G. R. (September 1996). "The mechanism of action of cyclosporin A and FK506". Clinical Immunology and Immunopathology 80 (3 Pt 2): S40–45. doi:10.1006/clin.1996.0140. ISSN 0090-1229. PMID 8811062.
- ↑ Ramachandran, G. N.; Sasisekharan, V. (1968). "Conformation of polypeptides and proteins". Advances in Protein Chemistry 23: 283–438. doi:10.1016/S0065-3233(08)60402-7. ISBN 9780120342235. ISSN 0065-3233. PMID 4882249.
- ↑ Fischer, G.; Aumüller, T. (2003). "Regulation of peptide bond cis/trans isomerization by enzyme catalysis and its implication in physiological processes". Reviews of Physiology, Biochemistry and Pharmacology 148: 105–150. doi:10.1007/s10254-003-0011-3. ISBN 978-3-540-40136-0. ISSN 0303-4240. PMID 12698322.
- ↑ Prakash, Ajit; Shin, Joon; Rajan, Sreekanth; Yoon, Ho Sup (2016-04-07). "Structural basis of nucleic acid recognition by FK506-binding protein 25 (FKBP25), a nuclear immunophilin". Nucleic Acids Research 44 (6): 2909–2925. doi:10.1093/nar/gkw001. ISSN 0305-1048. PMID 26762975.
External links
- [1]Immunophilins at the US National Library of Medicine Medical Subject Headings (MeSH)
- "Plant immunophilins and signal transduction" at berkeley.edu
- http://www.jbc.org/content/280/26/24308.full
Original source: https://en.wikipedia.org/wiki/Immunophilins. Read more
- ↑ "Neural actions of immunophilin ligands". http://sabatinilab.wi.mit.edu/Sabatini%20papers/Snyder2.pdf.
- ↑ Snyder, Solomon; Sabatini, David (January 1998). "Neural actions of immunophilin ligands". Trends in Pharmacological Sciences 19 (1): 21–26. doi:10.1016/s0165-6147(97)01146-2. PMID 9509898. http://sabatinilab.wi.mit.edu/Sabatini%20papers/Snyder2.pdf.
