PHYLOGENIC RELATIONSHIPS OF THE AMINO-ACID-SEQUENCES OF PROSOME (PROTEASOME, MCP) SUBUNITS

Prosomes [or proteasomes, Multi-Catalytic Proteinase (MCP)] are multis ubunit protein complexes, found from archaebacteria to man, the struct ure of which (a 4-layer cylinder) is remarkably conserved. They were f irst observed as subcomplexes of untranslated mRNP, and then as a mult icatalytic proteinase with several proteolytic activities. A number of sequences from subunits of these complexes are now available. Analysi s of the sequences shows that these subunits are evolutionarily relate d, and reveals three highly conserved amino acid stretches. Based on a phylogenic approach, we propose to classify the sequenced subunits in to 14 families, which fall into two superfamilies, of the alpha- and b eta-type. These data, together with several recently published observa tions, suggest that some subunits may be interchangeable within the co mplexes, which would thus constitute a population of heterogenous part icles.