Figure 1. Identification of two major elytral cuticle proteins from T. castaneum.

Extracts of SDS-soluble proteins from elytra dissected from newly emerged adults were analyzed by SDS-PAGE. The two major proteins (subsequently named TcCPR27 and TcCPR18), with apparent sizes of 10 and 20 kDa, respectively, were digested with trypsin, and the resulting peptides were analyzed by MALDI-TOF mass spectrometry (see Figure S1 and Table S1). Amino acid sequences deduced from cloned cDNA sequences for each protein are shown on the left. Both proteins contain an RR-2 motif (highlighted in gray). Predicted secretion signal peptides are underlined. In both TcCPR27 and TcCPR18, the amino-terminal residue of the mature forms after secretion (Gln 20) is apparently modified to pyroglutamic acid (Table S1).