Pain peptides. Solution structure of orphanin FQ2

Orphanin FQ2 (OFQ2) is a novel heptadecapeptide generated from prepronocice ptin (PPNOC), the same precursor of nociceptin/orphanin FQ and nocistatin, OFQ2 is a potent analgesic when administered both supraspinally and spinall y. In order to clarify the structural relationship with all peptides genera ted from PPNOC, we have undertaken the conformational study of OFQ2 in wate r and in structure-promoting solvent media. Nuclear magnetic resonance data and theoretical calculations are consistent with a well defined helical st ructure from Met(5) to Ser(16). The uniform distribution of hydrophobic res idues along the helix suggests that OFQ2 may interact with the transmembran e helices of a receptor akin to those of nociceptin and opioids, (C) 2000 F ederation of European Biochemical Societies.