Structure of chicken hypothalamic luteinizing hormone-releasing hormone. II. Isolation and characterization.

Avian luteinizing hormone-releasing hormone (LH-RH) has been isolated from 249,000 chicken hypothalami and shown to differ structurally from mammalian hypothalamic LH-RH. Purification was achieved by acetic acid extraction, anti-LH-RH affinity chromatography, and cation exchange and reverse phase high performance liquid chromatography. The isolated peptide eluted as a single peak on reverse phase high performance liquid chromatography. Acid hydrolysis of the peptide yielded integral molar ratios of amino acids and a composition identical with that of mammalian decapeptide LH-RH, except for the presence of an additional glutamic acid residue and the absence of arginine. The isoelectric point of chicken LH-RH (7.3) is consistent with the glutamic acid representing a glutamine residue. We therefore synthesized [Gln8]LH-RH and established that it has chromatographic properties identical with natural chicken LH-RH. These studies indicate that the structure of chicken hypothalamic LH-RH is: pGlu-His-Trp-Ser-Tyr-Gly-Leu-Gln-Pro-Gly-NH2.