Immunoaffinity purification of the neuropeptide prothoracicotropic hormone from Manduca sexta

The prothoracicotropic hormones (PTTH) are cerebral peptides that control insect postembryonic development by stimulating the prothoracic glands to synthesize ecdysteroids. Using immunoaffinity chromatography and 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-separated fragments of this acidic peptide were sequenced and exhibited no sequence similarity with Bombyx mori PTTH. In agreement with this finding, the basic Bombyx PTTH had no PTTH bioactivity in Manduca. One sequenced fragment of the Manduca PTTH is approximately 70% similar to the vertebrate cellular retinoid binding proteins, suggesting these binding proteins may be present in insects.