CLONING AND SEQUENCING A NON-ATPASE SUBUNIT OF THE REGULATORY COMPLEXOF THE DROSOPHILA 26S-PROTEASE

We have cloned and sequenced a non-ATPase subunit of the regulatory co mplex of the Drosophila 26S protease. The gene is present in a single copy in the Drosophila genome. By comparing the nucleotide sequence of the genomic and cDNA clones three exons and two introns were localize d. Two transcription start sites were identified 9 bp apart. The deduc ed protein sequence shows no significant similarity to any other prote in in the database. In Drosophila embryos where the 26S protease is pr esent in high concentration, the pool of free subunits of the regulato ry complex is very low. Among the free subunits of the regulatory comp lex the cloned subunit is present in very large excess. This observati on raises the possibility that this subunit is in a dynamic equilibriu m, exchanging between a free and a particle-bound form, which may have important implications concerning its function.