Primary Structure of the Ovine Hypothalamic Luteinizing Hormone-Releasing Factor (LRF)

Abstract

The primary structure of ovine hypothalamic hypophysiotropic luteinizing hormone-releasing factor, LRF, has been established as pGlu-His-Trp-SerTyr-Gly-Leu-Arg-Pro-Gly-NH2 by hydrolysis of the peptide with chymotrypsin or pyrrolidone-earboxylylpeptidase and by analysis of the products by an Edman-dansylation sequencing technique, as well as by mass spectrometry of the derived phenylthiohydantoins. A decapeptide with the proposed primary structure, prepared by total synthesis, gave the same result on sequencing. The synthetic decapeptide possesses the same biological activities as the native ovine LRF. The amino-acid sequence of ovine LRF is identical to that already published for porcine LRF.Various areas of the central nervous system participate in the fine regulation of the secretion of all adenohypophysial hormones. The ultimate integrator of information originating in the central nervous system is the hypothalamus. The final information from the hypothalamus to the adenohypophysis is not transmitted in the form of nerve impulses, but is carried in the form of specific hypothalamic hypophysiotropic substances, the hypothalamic releasing factors, that are carried through the hypothalamo-hypophysial portal system of capillaries from the median eminence region of the ventral hypothalamus to the cells of the adenohypophysis. There is good physiological evidence that such a hypothalamic control is involved in the secretion of the gonadotropin, luteinizing hormone. In the early 1960s, several investigators reported experimental results that were best explained by proposing the existence of substances that specifically stimulated the secretion of luteinizing hormone, and that were probably polypeptides, in crude aqueous extracts of hypothalamic tissues of various mammalian species (1-3). Preparations of LRF, active at 1 /Ag per dose in animal bioassays, were obtained by gel filtration and ion-exchange chromatography on carboxymethylcellulose (4), an observation that was confirmed by similar methods by several investigators (5, 6). In spite of the vagaries of the various bioassay methods available, several laboratories reported preparations of LRF of increased potency (5, 6). Several of these early publications led to contradictory statements regarding purification and separation of LH-releasing factor (LRF), from a follicle-stimulating hormone releasing factor (5, 7). Two laboratories independently reported the isolation of porcine LRF (8) and ovine LRF (9), both groups concluding that LRF from either species was a nonapeptide containing, on the basis of acid hydrolysis, 1 His, 1 Arg, 1 Ser, 1 Glu, 1 Pro, 2 Gly, 1 Leu, 1 Tyr. Earlier results with the pyrrolidone-carboxylylpeptidase prepared by Fellows and Mudge (10) had led us to conclude (11) that the Nterminal residue of LRF was Glu in its cyclized pyroglutamic (pGlu) form, as in the case of hypothalamic TRF, (pGluHis-Pro-NH2).While our own studies on the amino-acid sequence of ovine LRF were in progress, Matsuo et al. (12) reported that porcine LRF contai...

Isolation, primary structure, and synthesis of α-endorphin and γ-endorphin, two peptides of hypothalamic-hypophysial origin with morphinomimetic activity

“…Sequential degradation of peptides was performed using the Edman method followed by dansylation with [14C]dansyl chloride and identification of Pthderivatives by mass spectrometry as previously described (8,10).…”

Isolation and characterisation of mRNA encoding the salmon- and chicken-II type gonadotrophin-releasing hormones in the teleost fish Rutilus rutilus (Cyprinidae)

“…Burgus et al 1972, Miyamoto et al 1984, Sherwood et al 1986, Hayes et al 1994, cDNAs isolated from roach-encoded peptides with tripartite structures. Both sGnRH and cGnRH-II precursor mRNA encodes a signal peptide, the GnRH and a GnRH associated peptide (GAP).…”

The GnRH system in the European sea bass (Dicentrarchus labrax)

“…To date, fourteen forms of GnRH decapeptides have been found in vertebrates, in which at least one unique form has been determined from a representative species of all vertebrate classes. Ten GnRH forms out of the fourteen were found in fish and six of them in teleosts: chicken GnRH II (cGnRH II; Miyamoto et al 1984), mammalian GnRH (mGnRH; Matsuo et al 1971, Burgus et al 1972, salmon GnRH (sGnRH; Sherwood et al 1983), catfish GnRH (cfGnRH; Ngamvongchon et al 1992), sea bream GnRH (sbGnRH; Powell et al 1994), herring GnRH (hGnRH;Carosfeld et al 2000) and Medaka GnRH (mdGnRH; Okubo et al 2000). cGnRH II is present in all vertebrate classes examined to date, and the mGnRH form is present in primitive non-teleostean bony fish, primitive teleosts (eels and others), amphibians and mammals.…”