Characterization of three structurally-related 8–9 kDa monomeric peptides present in the Corpora cardiaca of Locusta: A revised structure for the neuroparsins

Recent developments in automated peptide microsequencing, liquid secondary-ion and electrospray mass spectrometry enable unambiguous primary structure determinations of minute amounts of biological material. We have used these methods in combination to characterize the predominant peptides from HPLC eluates of aqueous extracts of corpora cardiaca from adults of Locusta migratoria. Among the molecules or families of molecules clearly predominating in the extracts, we had previously characterized novel peptides (Hietter et al., 1989, 1990), and we recently identified three structurally-related, cysteine-rich, 8–9 kDa peptides. We present in this paper their complete structure determination. The amino acid sequence of these peptides is superimposable to that of neuroparsins isolated as dimers by Girardie et al., 1989. However, our experimental data lead us to propose that these molecules are monomers containing six intramolecular disulfide bridges.