Bombyx and Manduca prothoracicotropic hormones: an immunologic test for relatedness.

Prothoracicotropic hormone (PTTH) controls the synthesis of ecdysteroids (molting hormones) by the insect prothoracic gland and thereby plays a critical role in insect growth, molting, and metamorphosis. PTTH has been purified, and cDNA clones obtained, from only one insect, the silkmoth Bombyx mon. Recently, a partial amino acid sequence was obtained for-a putative PTTH from the tobacco hornworm, Manduca sexta, and the data suggested an unexpected homology to a vertebrate retinoid binding protein rather than to the Bombyx PTTH.