The cDNA-structure of the prothoracicotropic hormone (PTTH) of the silkmoth Hyalophora cecropia.

The structure of the prothoracicotropic neurohormone (PTTH) of the silkmoth Hyalophora cecropia was elucidated at the cDNA level. The identified cDNA of 803 nt, which is over 90% identical with the corresponding part of the Samia cynthia ricini PTTH gene, encodes a preprohormone of 240 amino acids. Presence of proteolytic cleavage sites indicates that the preprohormone is split into a signal peptide, an intercalated peptide (64 residues), and the PTTH monomer (125 residues). Preprohormones of H. cecropia, S. c. ricini, Antheraea pernyi, and Bombyx mori diversified considerably in all these parts, indicating that the evolution of PTTH is unusually fast. Since a similarly rapid, and concerted evolution of the corresponding receptor is unlikely, the PTTH activity probably depends on the conservation of relatively few amino acids allowing proper molecular folding.