Molecular cloning of the Drosophila virilis larval glue protein gene Lgp-3 and its comparative analysis with other Drosophila glue protein genes.

DNA comprising the larval glue protein gene Lgp-3 of Drosophila virilis was isolated from a lambda genomic and a cDNA library. The transcription start site, two polyadenylation sites and the boundaries of the single intron were determined. An open reading frame encoding 379 amino acids was found. At the DNA level the presence of similar introns and three conserved sequence motifs in the proximal promoters suggest that the gene is related to those of the D. virilis lgp-1 and the D. melanogaster sgs-3, -7 and -8 glue proteins. Their common ancestry is also substantiated by the comparisons of the deduced amino acid sequences and the profiles of hydropathic indices, which reveal striking similarities of the N- and C-termini and of the central repeat domains, although the lengths and the primary structures of the proteins diverged considerably during 60 million years of separate evolution of the two Drosophila species.