Primary structure and biological activity of a third gonadotropin-releasing hormone from lamprey brain.
Previous studies have led to the identification of two molecular forms of GnRH (GnRH-I and II) in the brain of the sea lamprey, Petromyzon marinus. From analysis of these two forms, the primary structure of GnRH-I and the amino acid composition of GnRH-II were determined. We have now isolated a third molecular form of GnRH (GnRH-III) from the brain of this species that is different from GnRH-I and -II. The primary structure of GnRH-III is pGlu-His-Trp-Ser-His-Asp-Trp-Lys- Pro-Gly-NH2. A synthetic decapeptide with this amino acid sequence was chromatographically identical to natural GnRH-III. Intraperitoneal injection of synthetic lamprey GnRH-III (0.1 microgram/g) produced a significant (P < 0.05) elevation of plasma progesterone (31% over basal values) in female lampreys that was comparable to that produced by the same dose of lamprey GnRH-I (36% over basal). The elevation in plasma estradiol produced by lamprey GnRH-III (244% over basal) was significantly (P < 0.05) less than the elevation produced by GnRH-I (322% over basal). We propose based on the biological activity of lamprey GnRH-III in these studies and the occurrence of this peptide during metamorphosis in lampreys, that both lamprey GnRH-I and -III are neurohormones involved in reproduction in lampreys.
Sower
S A
SA
Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham 03824.
Chiang
Y C
YC
Lovas
S
S
Conlon
J M
JM
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000502:physiology*; D001923:Brain Chemistry; D002645:Chickens; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005399:Fishes; D007987:Gonadotropin-Releasing Hormone / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D007798:Lampreys; D008297:Male; D008322:Mammals; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid
D007987:Gonadotropin-Releasing Hormone