Proteasome 26S Subunit, Non ATPase 9 (PSMD9)

PSMD9 encodes a non-ATPase subunit of the 19S regulator.Sequence analysis predicted that the 222-amino acid Bridge-1 protein shares 98% amino acid similarity with human PSMD9 over the first 184 amino acids but diverges in the C terminus Bridge-1 contains a PDZ-like domain from amino acids 138 to 178, forming 3 beta sheets and 2 alpha helices. SDS-PAGE analysis showed that Bridge-1 is expressed as a 28-kD protein, close to the deduced value of 25 kD. Using Bridge-1 cDNA as probe, Northern blot analysis detected a 1.0-kb transcript in all rat and human tissues tested, with highest expression in pancreas, testis, kidney, and liver. Immunocytochemistry assessment demonstrated predominant nuclear localization of Bridge-1, with lower levels in cytoplasm.