BQ-123
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BQ-123, also known as cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu-), is a cyclic pentapeptide that was first isolated from a fermentation broth of '' Streptomyces misakiensis'' in 1991. NMR studies indicate that the polypeptide backbone consists of a type II beta turn and an inverse gamma turn. The side-chains adopt different orientations depending on the solvent used. The
proline Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the p ...
carbonyl oxygen atom located at the onset of a beta turn is a sodium ion binding site. It has a high affinity for sodium ions and can coordinate up to three of them. Studies have shown that BQ123 is effective in reversing Ischemia-induced acute renal failure, and it has been suggested that this might be because BQ123 increases reabsorption of sodium ions in the
proximal tubule The proximal tubule is the segment of the nephron in kidneys which begins from the renal (tubular) pole of the Bowman's capsule to the beginning of loop of Henle. At this location, the glomerular parietal epithelial cells (PECs) lining bowman’s ...
cells. BQ-123 is a selective ETA
endothelin receptor antagonist An endothelin receptor antagonist (ERA) is a drug that blocks endothelin receptors. Three main kinds of ERAs exist: * Dual ET Receptor Antagonists, which affect both endothelin A (ETA) and B receptors (ETB)CPU0213 21780-32-9is an example of a ...
. As such, it is used as a biochemical tool in the study of
endothelin receptor There are at least four known endothelin receptors, ETA, ETB1, ETB2 and ETC, all of which are G protein-coupled receptors whose activation result in elevation of intracellular-free calcium, which constricts the smooth muscles of the blood vessels ...
function. BQ-123 works as an ET-1 antagonist by reversing already established contractions to ET-1. This indicates that BQ-123 can work as an antagonist to remove ET-1 from its receptor (ETA).


References

{{Portal bar, Chemistry, Science Pyrrolidines Endothelin receptor antagonists Cyclic peptides Pentapeptides N-Acyltryptamines