Cloning and sequencing of the gene encoding the large (alpha-) subunit of the proteasome from Thermoplasma acidophilum

The gene encoding the alpha-subunit of the proteasome from the archaebacterium Thermoplasma acidophilum was cloned and sequenced. The gene encodes for a polypeptide with 233 amino acid residues and a calculated molecular weight of 25870. Sequence similarity of the alpha-subunit with the Saccharomyces cerevisiae wild-type suppressor gene scll+ encoded polypeptide, which is probably identical with the subunit YC7-alpha of the yeast proteasome, lends support to a putative role of proteasomes in the regulation of gene expression. The significant sequence similarity to the various subunits of eukaryotic proteasomes make it likely that proteasomal proteins are encoded by one gene family of ancient origin.