ISOLATION, IDENTIFICATION AND SYNTHESIS OF LOCUSTAMYOTROPIN-III AND LOCUSTAMYOTROPIN-IV, 2 ADDITIONAL NEUROPEPTIDES OF LOCUSTA-MIGRATORIA - MEMBERS OF THE LOCUSTAMYOTROPIN PEPTIDE FAMILY

Two neuropeptides, locustamyotropin III (Lom-MT III) and locustamyotropin IV (Lom-MT IV) were isolated from 9000 brain-corpora cardiaca-corpora allata-suboesophageal ganglion complexes of the migratory locust, Locusta migratoria. They were purified by reversed phase and normal phase high performance liquid chromatography and detected by a Leucophaea hindgut motility bioassay. Amino acid composition and sequence analysis combined with enzymatic digestion established the primary structure of Lom-MT Ill as Arg-Gln-Gln-Pro-Phe-Val-Pro-Arg-Leu and of Lom-MT IV as Arg-Leu-His-Gln-Asn-Gly-Met-Pro-Phe-Ser-Pro-Arg-Leu. Both candidate peptide sequences were synthesized and both chromatographic and biological properties of the synthetic peptides in the amide form were the same as those of the native peptides thus confirming the structural analysis. Both peptides have a Phe-X-Pro-Arg-Leu-NH2 carboxyl terminus and hence, are the third and fourth members of the locustamyotropin peptide family. This carboxyl terminal sequence is also found in other insect peptides and has a stimulating effect on pheromone biosynthesis and cuticular melanisation (PBAN/MRCH in Bombyx mori and Heliothis zea) and on myogenic hindgut contractions (leucopyrokinin in Leucophaea maderae). Like the other locustamyotropins, Lom-MT III and IV stimulate contractions of the oviduct in the locust.