Isolation and amino acid sequence of the TRH-potentiating peptide from bovine hypothalamus.

A neuropeptide termed TRH-potentiating peptide, which potentiates TRH-evoked thyrotropin secretion by antehypophysis in vitro, was isolated from an acetonic powder of bovine hypothalamus. The peptide was purified to homogeneity by a 3-step protocol involving molecular sieve filtration, ion-exchange chromatography and reverse phase high performance liquid chromatography. The complete amino acid sequence of the decapeptide was determined as Ser-Phe-Pro-Trp-Met-Glu-Ser-Asp-Val-Thr by automated Edman degradation with a solid-phase sequencer. Bovine TRH-potentiating peptide is structurally identical to Ps4, a decapeptide which was deduced from the cDNA encoding the rat TRH precursor. This study provides for the first time a direct chemical evidence for the existence of non-TRH peptides originating from posttranslational processing of the TRH precursor in vivo.