Identification, molecular cloning, and characterization of subunit 11 of the human 26S proteasome

We sequenced five peptides from subunit II (S11), a 43 kDa protein of the h uman 26S proteasome, and used this information to clone its cDNA, The S11 c DNA encodes a 376 amino acid protein with a pI of 5.6 and a molecular mass of 42.9 kDa, Translation of SII RNA in the presence of [S-35]methionine pro duces a radiolabeled protein that co-migrates with S11 of the human 26S pro teasome on SDS-PAGE, Polyclonal antiserum made against recombinant S11 reco gnizes a protein of the same size in extracts of bacteria expressing S11 an d in purified 26S proteasomes from human red blood cells or rabbit reticulo cytes. The S11 sequence does not contain motifs that suggest a biological f unction. SII is, however, the human homolog of Rpn9, a recently identified subunit of the yeast 26S proteasome, (C) 1999 Federation of European Bioche mical Societies.