RF-AMIDE PEPTIDES ISOLATED FROM THE MIDGUT OF THE CORN-EARWORM, HELICOVERPA-ZEA, RESEMBLE PANCREATIC-POLYPEPTIDE

The midgut of the corn earworm, Helicoverpa zea, contains endocrine ce lls which exhibit immunoreactivity resembling Phe-Met-Arg-Phe-NH2 (FMR Fa), a molluscan cardioactive peptide and a member of a recognized fam ily of molecules termed RF-amide peptides. An extract of 10 000 midgut s was fractionated by HPLC and FMRFa immunoreactivity was determined b y radioimmunoassay (RTA). Two peptides were isolated and their sequenc es determined by tandem mass spectroscopy were: Gln-Ala-Ala-Arg-ProArg -Phe-NH2 and Ala-Ala-Arg-Pro-Arg-Phe-NH2. These new peptides are terme d Hez-MP-I and Hez-MP-II, respectively. Their sequences resemble the c arboxyl terminal tetrapeptide of (a) the pancreatic polypeptides of lo wer vertebrates and (b) a related neuropeptide from squid. An antiseru m was raised against Hez-MP-I to develop a specific RIA, which was use d with HPLC to demonstrate that each of these peptides occur in hemoly mph, as well as in midgut and brain. Hez-MPs thus qualify as putative hormones which may play a role in coordination of digestion in this in sect. (C) 1998 Elsevier Science Ltd. All rights reserved.