cDNA cloning of a new type of subunit of mammalian proteasomes.

The primary structure of a new type of subunit (RN3) of rat proteasomes (multicatalytic proteinase complexes) has been determined from the nucleotide sequence of the cDNA. The cDNA encodes a protein of 232 amino acids but the directly determined N-terminal amino acid sequence suggests that the subunit is post-translationally processed to a M(r) = 24k form. Sequence alignments reveal a similarity of RN3 to other proteasome subunits. It can be designated a B-type proteasomal subunit but is not closely related to the beta subunit of the archaebacterial proteinase or to other members of the B group.