RF(Arg-Phe)amide family 26 amino acid peptide, also known as P518, is a human protein.[5]
The 26-amino acid RF-amide peptide, P518 functions as a high-affinity ligand of GPR103. Both GPR103 and P518 precursor mRNA exhibited highest expression in brain.[6] 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, suggesting that QRFP and GPR103 regulate adrenal function.[7]
Chartrel N, Bruzzone F, Dujardin C, et al. (2006). "Identification of 26RFa from frog brain: a novel hypothalamic neuropeptide with orexigenic activity in mammals". Ann. N. Y. Acad. Sci. 1040: 80–3. Bibcode:2005NYASA1040...80C. doi:10.1196/annals.1327.009. PMID15891009. S2CID21012765.
Thuau R, Guilhaudis L, Ségalas-Milazzo I, et al. (2005). "Structural studies on 26RFa, a novel human RFamide-related peptide with orexigenic activity". Peptides. 26 (5): 779–89. doi:10.1016/j.peptides.2005.01.006. PMID15808908. S2CID24088690.