Comparison of larval and pupal cuticular proteins in Tenebrio molitor

Abstract

Protein extracts from pupal and larval pharate cuticle from the meal worm, Tenebrio molitor, gave nearly identical patterns by two-dimensional electrophoresis and by ion-exchange chromatography. The main components in the cuticular extracts from the two metamorphic stages were also identical with respect to molecular mass according to electrospray ionization mass spectrometry. The complete amino acid sequence for one of the pupal cuticular proteins was determined; according to partial amino acid sequences and the mass spectrometric peptide map for the corresponding larval cuticular protein, it was concluded that the larval protein has the same amino acid sequence as the pupal protein. The sequence is characterized by a high content of alanine, proline, valine, and tyrosine and the complete absence of acidic amino acid residues, the sulphur containing amino acids and tryptophan. The sequence is further characterized by a high frequency of repeated sequence motifs, among which the Ala-Ala-Pro-Ala motif is the most abundant, but also longer sequence motifs are repeated. The sequence shows striking resemblance to sequences of proteins isolated from pharate locust cuticle.