Cyclic peptide

α-Amanitin

bacitracin

cyclosporine

Cyclic peptides (or cyclic proteins) are polypeptide chains whose amino and carboxyl termini are themselves linked together with a peptide bond that forms a circular chain. A number of cyclic peptides have been discovered in nature and they can range anywhere from just a few amino acids in length, to hundreds. Cyclic peptides can be classified according to the types of bonds that comprise the ring. Homodetic cyclic peptides, such as cyclosporine A, are those in which the ring is composed exclusively of normal peptide bonds (i.e. between the alpha carboxyl of one residue to the alpha amine of another). Cyclic isopeptides contain at least one non-alpha amide linkage, such as a linkage between the side chain of one residue to the alpha carboxyl group of another residue, as in microcystin and bacitracin. Cyclic depsipeptides, such as aureobasidin A and HUN-7293, have at least one lactone (ester) linkage in place of one of the amides. Some cyclic depsipeptides are cyclized between the C-terminal carboxyl and the side chain of a Thr or Ser residue in the chain, such as kahalalide F, theonellapeptolide, and didemnin B. Bicyclic peptides such as the amatoxins amanitin and phalloidin contain a bridging group, generally between two of the side chains. In the amatoxins, this bridge is formed as a thioether between the Trp and Cys residues. Other bicyclic peptides include echinomycin, triostin A, and Celogentin C. There are a number of cyclic peptide hormones which are cyclized through a disulfide bond between two cysteines, as in somatostatin and oxytocin.

The processes by which cyclic peptides are formed in cells are not yet fully understood. One interesting property of cyclic peptides, however, is that they tend to be extremely resistant to the process of digestion, enabling them to survive intact in the human digestive tract. This trait makes cyclic peptides attractive to designers of protein-based drugs that may be used as scaffolds which, in theory, could be engineered to incorporate any arbitrary protein domain of medicinal value, in order to allow those components to be delivered orally. This is especially important for delivery of other proteins that would be destroyed without such implementation.

Examples include:

• amanitins
• bacitracin
• colistin
• cyclosporine
• cyclotide
• dactinomycin
• daptomycin
• nisin
• polymyxin b
• pristinamycin
• octreotide
• valinomycin

See also

• nonribosomal peptide

References

David J. Craik (17 March 2006). "Seamless Proteins Tie Up Their Loose Ends". Science 311 (5767): 1563–7. doi:10.1126/science.1125248. PMID 16543448. http://www.sciencemag.org/cgi/content/summary/311/5767/1563. 

External links

• Cybase
• MeSH Cyclic+Peptides

This membrane protein-related article is a stub. You can help Wikipedia by expanding it.v · Categories: Peptides Peripheral membrane proteins Membrane protein stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем написать курсовую Brig (district) Long Island order of battle Look at other dictionaries: Peptide synthesis — In organic chemistry, peptide synthesis is the production of peptides, which are organic compounds in which multiple amino acids are linked via peptide bonds which are also known as amide bonds. The biological process of producing long peptides… …   Wikipedia Cyclic guanosine monophosphate — IUPAC name 2 amino 9 [(1S,6R,8R,9R) 3,9 dihydroxy 3 oxo 2,4,7 trioxa 3λ5 phosphabicyclo[4 …   Wikipedia Cyclic nucleotide-gated ion channel — Cyclic nucleotide gated (CNG) ion channels are ion channels that function in response to the binding of cyclic nucleotides. CNG channels are nonselective cation channels that are found in the membranes of various types of cells. Signal… …   Wikipedia cyclic adenosine monophosphate — n CYCLIC AMP * * * (3‵,5‵ AMP) (cAMP) (cyclic AMP) a cyclic nucleotide, adenosine 3′,5′ cyclic monophosphate, that serves as an intracellular and, in some cases, extracellular “second messenger” mediating the action of …   Medical dictionary Peptide — Peptides redirects here. For the journal, see Peptides (journal). A tetrapeptide (example Val Gly Ser Ala) with green marked amino end (L Valine) and …   Wikipedia peptide — A compound of two or more amino acid s in which a carboxyl group of one is united with an amino group of another, with the elimination of a molecule of water, thus forming a p. bond, –CO–NH–; i.e., a substituted amide. Cf.:eupeptide bond …   Medical dictionary cyclic citrullinated peptide — (CCP) a synthetic, citrulline containing peptide with a cyclic structure, used in assays for rheumatoid arthritis; the presence of antibodies to this peptide is highly specific for rheumatoid arthritis …   Medical dictionary Nonribosomal peptide — Nonribosomal peptides (NRP) are a class of peptide secondary metabolites, usually produced by microorganisms like bacteria and fungi. Nonribosomal peptides are also found in higher organisms, such as nudibranchs, but are thought to be made by… …   Wikipedia Formyl peptide receptor — protein Name=formyl peptide receptor 1 caption= width= HGNCid=3826 Symbol=FPR1 AltSymbols= EntrezGene=2357 OMIM=136537 RefSeq=NM 002029 UniProt=P21462 PDB= ECnumber= Chromosome=19 Arm=q Band=13.41 LocusSupplementaryData=protein Name = formyl… …   Wikipedia Brain natriuretic peptide — Natriuretic peptide B Identifiers Symbols NPPB; BNP External IDs OMIM:  …   Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”