THE 20S PROTEASOME OF STREPTOMYCES-COELICOLOR

20S proteasomes were purified from Streptomyces coelicolor A3(2) and s hown to be built from one alpha-type subunit (PrcA) and one beta-type subunit (PrcB). The enzyme displayed chymotrypsin-like activity on syn thetic substrates and was sensitive to peptide aldehyde and peptide vi nyl sulfone inhibitors and to the Streptomyces metabolite lactacystin. Characterization of the structural genes revealed an operon-like gene organization (prcBA) similar to Rhodococcus and Mycobacterium spp. an d showed that the beta subunit is encoded with a 53-amino-acid propept ide which is removed during proteasome assembly. The upstream DNA regi on contains the conserved orf7 and an AAA ATPase gene (arc).