Abstract
A novel form of gonadotropin-releasing hormone (GnRH) had been recently isolated and characterized from the gilthead seabream (Sparus aurata). This novel form, designated sbGnRH, was suggested to be the endogenous stimulator of gonadotropin release. This paper reports on the isolation and characterization of a 360-bp cDNA encoding the complete sbGnRH precursor. This precursor is composed of a 25 amino acid leader sequence, the biologically active sbGnRH, the cleavage site (Gly-Lys-Arg), and a 57 amino acid associated peptide (GAP). Comparison of the nucleotide and amino acid sequence of the sbGnRH precursor with precursors of other GnRH forms places the sbGnRH precursor evolutionarily closer to the mammalian GnRH and chicken GnRH-I, which have also been shown to be the relevant forms for gonadotropin release in mammals and birds, respectively. The characterization of the sbGnRH precursor cDNA lays the foundation for future studies aimed toward understanding the neuroendocrine control of reproduction in seabream and other fish species.