Larval salivary gland secretion proteins in Drosophila structural analysis of the Sgs-5 gene.

The structure of the Drosophila melanogaster salivary gland secretion gene Sgs-5 has been determined by DNA sequence analysis of cloned genomic DNA. This developmentally and tissue-specific gene is a member of the third instar intermolt gene set and is under control of the insect molting hormone ecdysterone. RNA protection experiments show that the RNA coding region of Sgs-5 contains 769 nucleotides and is divided into three exons by two small introns. The protein-coding region appears to begin after a short untranslated RNA leader (33 nucleotides) and to result in a protein of 163 amino acids. The first 18 amino acids give the amino-terminal end the highly hydrophobic nature characteristic of a signal peptide.