RFamide family 26 amino acid peptide, also known as P518, is a human protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

.

The 26-amino acid RF-amide peptide, P518 functions as a high-affinity ligand of GPR103

GPR103

Pyroglutamylated RFamide peptide receptor also known as orexigenic neuropeptide QRFP receptor or G-protein coupled receptor 103 is a protein that in humans is encoded by the QRFPR gene.-Function:...

. Both GPR103 and P518 precursor mRNA exhibited highest expression in brain. The 43-amino acid QRFP peptide, a longer form of the P518 peptide is necessary to exhibit full agonistic activity with GPR103. Intravenous administration QRFP caused release of aldosterone

Aldosterone

Aldosterone is a hormone that increases the reabsorption of sodium ions and water and the release of potassium in the collecting ducts and distal convoluted tubule of the kidneys' functional unit, the nephron. This increases blood volume and, therefore, increases blood pressure. Drugs that...

, suggesting that QRFP and GPR103 regulate adrenal function.

Further reading