Cuticular proteins from the giant cockroach, Blaberus craniifer

The extractable proteins from selected cuticular regions of nymphs and adults of the cockroach, Blaberus craniifer, have been compared by two-dimensional gel-electrophoresis. Only minor differences in protein patterns were observed when nymphal and adult pre-ecdysial cuticles (presumptive exocuticle) were compared, whereas the pattern obtained from nymphal mid-instar cuticle (mainly endocuticle) differed markedly from that obtained from mature adult cuticle. The pattern obtained from nymphal mid-instar cuticle depended upon the specific cuticular region analysed, but the differences within a stage were, to a large extent, quantitative and not qualitative. Seven nymphal endocuticular proteins have been purified to near homogeneity, and the complete amino acid sequence has been determined for three of them. One of the proteins, Bc-NCP1, contains a 16-residue motif repeated three times and containing a disulphide bridge. Protein Bc-NCP2 has a twice repeated motif in common with a pupal protein from Bombyx mori, and Bc-NCP4 contains a twice-repeated sequence of nine residues and is moreover characterized by an unusual high content of valine (22.0%). None of the protein sequences shows significant similarities to the sequences determined for locus endocuticular proteins, except that they all have pyroglutamate as the N-terminal residue.