Tat-binding protein 7 is a subunit of the 26S protease

Subunit 6 (S6), an integral component of the 26S protease from human erythrocytes, has been studied by SDS-PAGE, peptide mapping and sequence analysis. S6 was cleaved with CNBr and three internal peptides were sequenced. A comparison with known proteins in Genbank revealed that all three S6 peptides match the predicted sequence of TBP7, Tat-binding protein 7. Based on peptide matches covering more than 10% of the TBP7 sequence, and the fact that the migration of S6 on SDS-PAGE is consistent with the estimated molecular mass for TBP7, we conclude that subunit 6 of the 26S protease is TBP7.