The procuticle of Drosophila: heterogeneity of urea-soluble proteins

Proteins, soluble in 7 M urea, 4 M guanidine hydrochloride, or 2% sodium dodecyl sulfate, have been extracted from untanned larval cuticles of Drosophila melanogaster. A major protein fraction, apparent molecular weight 8000 - 10 000, is resolved into eight different components (five major, three minor) by gradient gel electrophoresis under nondenaturing conditions. Proteins extracted in 7 M urea have been resolved by diethylaminoethylcellulose chromatography into five fractions, three of which are greatly enriched for electrophoretically homogeneous proteins. The five fractions have different amino acid compositions. Electrophoretic variants involving four of the five major proteins have been obtained. Preliminary genetic analysis indicates that at least three of the five proteins are specified by separate structural genes.