CDNA CLONING AND FUNCTIONAL-ANALYSIS OF P44.5 AND P55, 2 REGULATORY SUBUNITS OF THE 265-PROTEASOME

We have employed cDNA cloning to deduce the complete primary structure s of p44.5 and p55, two subunits of PA700, a 700-kDa multisubunit regu latory complex of the human 26S proteasome. These polypeptides consist of 422 and 456 amino acids with calculated molecular masses of 47463 and 52903, and isoelectric points of 6.06 and 7.56, respectively. Comp uter-assisted homology analysis revealed high sequence similarities of p44.5 and p55 with yeast proteins whose functions are yet unknown. Di sruption of the yeast genes, termed NAS4 and NAS5 (non-ATPase subunits 4 and 5), resulted in lethality, indicating that each of the two subu nits is essential for proliferation of yeast cells. (C) 1997 Elsevier Science B.V.