A FAMILY OF NEUROPEPTIDES THAT INHIBIT JUVENILE-HORMONE BIOSYNTHESIS IN THE CRICKET, GRYLLUS-BIMACULATUS

Four nonapeptides that inhibit juvenile hormone synthesis have been isolated by four high performance liquid chromatographic steps from extracts of the brain of the field cricket, Gryllus bimaculatus. The primary structures of these peptides were assigned by Edman degradation and mass spectrometry as Gly-Trp-Gln-Asp-Leu-Asn-Gly-Gly-Trp-NH2 (Grb-AST B1), Gly-Trp-Arg-Asp-Leu-Asn-Gly-Gly-Trp-NH2 (Grb-AST B2), Ala-Trp-Arg-Asp-Leu-Ser-Gly-Gly-Trp-NH2 (Grb-AST B3), and Ala-Trp-Glu-Arg-Phe-His-Gly-Ser-Trp-NH2 (Grb-AST B4). Each of the peptides shows high sequence similarity to the locustamyoinhibiting peptide (Lom-MIP), but is structurally different from all the allatostatins so far identified. The synthetic allatostatins Grb-AST B1-4 are potent inhibitors (50% inhibition at 10(-8) to 7 x 10(-8) M) of juvenile hormone III biosynthesis by corpora allata from 3 day-old virgin females of G. bimaculatus using an in vitro bioassay. At 10(-7) M, Grb-AST B1 also strongly inhibits juvenile hormone III biosynthesis by corpora allata from 2-day-old adult males and 1-day-old (males and females) and 4-day-old (females) last instar larvae of G. bimaculatus. The inhibitory effect of Grb-AST B1 was also evident on corpora allata from a related species, Acheta domesticus, Inhibition of juvenile hormone synthesis by Grb-AST B1-4 is reversible.