Proteasomes are large, multisubunit particles that act as the proteolytic machinery for most regulated intracellular protein breakdown in eukaryotic cells. The core proteinase of this complex, known as the 20S proteasome, is a hollow barrel-shaped structure made up of four stacked rings of seven subunits each, with the outer two rings each being made up of seven distinct alpha-type subunits, and the two inner rings composed of seven different beta-type subunits. Here we present the cloning, sequencing and genetic mapping of a Drosophila melanogaster gene, alpha5_dm, encoding one of the proteasome alpha subunits. This gene, which is homologous to the yeast PUP2 and the human Zeta genes, maps to chromosome 2 at position 54B3-5. The map positions of the previously cloned proteasome genes Pros25 and Pros29 were also determined, and found to lie at positions 87B and 57B, respectively. A search for other D. melanogaster alpha5_dm-like genes encoding potential isoforms of this subunit failed to identify any closely related genes.