A cuticular protein from the moulting stages of an insect.
A 22 kDa peptide was purified from prepupal cuticles of 5th instar Calpodes ethlius caterpillars. It was absent earlier in the stadium and from the egg and adult, i.e. it is related to cuticle turnover rather than cuticle structure. It was present at larval and metamorphic moults, showing that it is related to moulting not just metamorphosis. The cDNA corresponding to the 22 kDa peptide was isolated by antibody screening of an epidermal cDNA expression library. Hybridization to Calpodes genomic DNA showed that the gene was present as a single copy. The deduced amino acid sequence is not like any of the sequences of cuticular structural proteins that have been published, but has a 47 amino acid sequence similar to bacteriophage T7 N-acetylmuramoyl-L-alanine amidase (34% identical, 51% similar). The amino acid sequence, the timing of expression in development, and the similarity between the substrate of the bacteriophage amidase and components of insect cuticle, all suggest that the 22 kDa protein may have a role in cleaving chitin-peptide bonds as a prerequisite for digestion of the cuticle by chitinases and proteases.
Marcu
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Department of Zoology, University of Western Ontario, London, Canada.
Locke
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016384:Consensus Sequence; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D007814:Larva; D007915:Lepidoptera / Q000235:genetics / Q000254:growth & development*; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018978:Molting; D010063:Ovum / Q000502:physiology; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D011679:Pupa
C115045:CECP22 protein, Calpodes ethlius; D019476:Insect Proteins