Secondary structure of a crustacean neuropeptide hormone family by means of CD

Three hormonal neuropeptides have been purified from the sinus gland of the Mexican crayfish Procambarus bouvieri by means of a single-step HPLC method: The molt-inhibiting hormone (MIH) and two isoforms of the crustacean hyperglycemic hormone (CHH-B and CHH-C). Compositional analysis and partial characterization of three neuropeptides revealed such a high degree of homology that we consider them to be members of a family. Circular dichroic spectra of the three neuropeptides showed that the secondary structure of both isoforms of the CHH are very similar, but that there are important differences in secondary structure between MIH and the CHHs, especially in helix content and in disordered regions.