A tetrapeptide is a

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. ...

, classified as an oligopeptide, since it only consists of four amino acids joined by

peptide bond In organic chemistry, a peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 (carbon number one) of one alpha-amino acid and N2 ( nitrogen number two) of another, along a peptide or protein c ...

s. Many tetrapeptides are

pharmacologically Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...

active, often showing affinity and specificity for a variety of receptors in protein-protein signaling. Present in nature are both linear and cyclic tetrapeptides (CTPs), the latter of which mimics protein reverse turns which are often present on the surface of proteins and druggable targets. Tetrapeptides may be cyclized by a fourth peptide bond or other covalent bonds. Examples of tetrapeptides are: * Tuftsin (L-threonyl-L-lysyl-L-prolyl-L-arginine) is a peptide related primarily to the

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as Tumor immunology, cancer cells and objects such ...

function. * Rigin (glycyl-L-glutaminyl-L-prolyl-L-arginine) is a tetrapeptide with functions similar to those of tuftsin. * Postin (Lys-Pro-Pro-Arg) is the N-terminal tetrapeptide of

cystatin C Cystatin C or cystatin 3 (formerly gamma trace, post-gamma-globulin, or neuroendocrine basic polypeptide), a protein encoded by the CST3 gene, is mainly used as a biomarker of kidney function. Recently, it has been studied for its role in predicti ...

and an antagonist of tuftsin. * Endomorphin-1 (H-Tyr-Pro-Trp-Phe-NH₂) and

endomorphin-2 Endomorphin-2 (EM-2) is an endogenous opioid peptide and one of the two endomorphins. It has the amino acid sequence Tyr-Pro-Phe-Phe-NH2. It is a high affinity, highly selective agonist of the μ-opioid receptor, and along with endomorphin-1 (EM- ...

(H-Tyr-Pro-Phe-Phe-NH₂) are peptide amides with the highest known affinity and specificity for the μ opioid receptor. * Morphiceptin (H-Tyr-Pro-Phe-Pro-NH₂) is a casomorphin peptide isolated from β- casein. * Gluten exorphines A4 (H-Gly-Tyr-Tyr-Pro-OH) and B4 (H-Tyr-Gly-Gly-Trp-OH) are peptides isolated from gluten. * Tyrosine-MIF-1 (H-Tyr-Pro-Leu-Gly-NH₂) is an endogenous opioid modulator. * Tetragastrin (''N''-((phenylmethoxy)carbonyl)-L-tryptophyl-L-methionyl-L-aspartyl-L-phenylalaninamide) is the C-terminal tetrapeptide of gastrin. It is the smallest peptide fragment of gastrin which has the same physiological and pharmacological activity as gastrin. * Kentsin (H-Thr-Pro-Arg-Lys-OH) is a contraceptive peptide first isolated from female hamsters. * Achatin-I (glycyl-phenylalanyl-alanyl-aspartic acid) is a neuroexcitatory tetrapeptide from giant African snail (''Achatina fulica''). * Tentoxin (cyclo(''N''-methyl-L-alanyl-L-leucyl-''N''-methyl-''trans''-dehydrophenyl-alanyl-glycyl)) is a natural cyclic tetrapeptide produced by phytopathogenic fungi from genus '' Alternaria''. * Rapastinel (H-Thr-Pro-Pro-Thr-NH₂) is a

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. They may also be considered ligands which display both agonistic and antagonist ...

of the NMDA receptor. * HC-toxin, cyclo(D-Pro-L-Ala-D-Ala-L-Aeo), where Aeo is 2-amino-8-oxo-9,10-epoxy decanoic acid, is a virulence factor for the fungus '' Cochliobolus carbonum'' on its host,

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn ( North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. ...

. *

Elamipretide Elamipretide (also known as SS-31, , MTP-131 and Bendavia) is a small mitochondrially-targeted tetrapeptide (D-Arg-dimethylTyr-Lys-Phe-NH2) that appears to reduce the production of toxic reactive oxygen species and stabilize cardiolipin Cardioli ...

, (D-Arg-dimethylTyr-Lys-Phe-NH2) a drug candidate that targets mitochondria.

References

Peptides * {{Protein-stub

See also

References