ISOLATION AND IDENTIFICATION OF A DIURETIC HORMONE FROM THE MEALWORM TENEBRIO-MOLITOR

A diuretic hormone of unusual structure was isolated from extracts of whole heads of the mealworm Tenebrio molitor. The hormone is a 37-aa p eptide of 4371 Da, with the sequence SPTISITAPIDVLRKTWEQERARKQMVKNREFL NSLN. This peptide increases cAMP production in Malpighian tubules of T. molitor. The amino acid sequence reveals that this peptide is a mem ber of the family of sauvagine/corticotropin-releasing factor/urotensi n I-related insect diuretic hormones. The C-terminal sequence of this peptide is quite different from other members of this family, which ha ve a hydrophobic C terminus (isoleucinamide or valinamide). When align ed comparably, T. molitor diuretic hormone has a more hydrophilic C te rminus, leucylasparagine (free acid), In contrast to all other known d iuretic hormones of this family, this peptide has exceptionally low st imulatory activity on cAMP production in Malpighian tubules of Manduca sexta. However, at nanomolar concentrations it stimulates cAMP produc tion in Malpighian tubules of T. molitor. Diuretic hormones of this fa mily have been isolated previously from Lepidoptera, Orthoptera, Dicty optera, and Diptera. This appears to be the first diuretic hormone iso lated from a coleopteran insect.