IMMUNOAFFINITY PURIFICATION OF THE NEUROPEPTIDE PROTHORACICOTROPIC HORMONE FROM MANDUCA-SEXTA

The prothoracicotropic hormones (PTTH) are cerebral peptides that cont rol insect postembryonic development by stimulating the prothoracic gl ands to synthesize ecdysteroids. Using immunoaffinity chromatography a nd SDS-PAGE, a 25.5 kDa big PTTH has been purified from Manduca sexta. Based upon SDS-PAGE and Western blot analysis, the native form of big PTTH appears to be a dimer with monomers of 16.5 kDa. Four HPLC-separ ated fragments of this acidic peptide were sequenced and exhibited no sequence similarity with Bombyx mori PTTH. In agreement with this find ing, the basic Bombyx PTTH had no PTTH bioactivity in Manduca. One seq uenced fragment of the Manduca PTTH is approximately 70% similar to th e vertebrate cellular retinoid binding proteins, suggesting these bind ing proteins may be present in insects.