PEPTIDE SEQUENCING IDENTIFIES MSS1, A MODULATOR OF HIV TAT-MEDIATED TRANSACTIVATION, AS SUBUNIT-7 OF THE 26-S PROTEASE

Subunit 7 is an integral component of the human erythrocyte 26 S prote ase. Peptide sequence analysis reveals that 22 amino acids from the N- terminus of subunit 7 correspond exactly to the N-terminus of MSS1, a modulator of HIV gene expression. Additional internal peptides from su bunit 7 obtained by CNBr cleavage also match 100% with the deduced ami no acid sequence of MSS1. Based on the fact that directly sequenced pe ptides from subunit 7 are identical to more than 12% of the hypothetic al translation product of MSS1, and the fact that the molecular weight of subunit 7 (49 kDa) corresponds to the predicted molecular weight o f MSS1 (48,633 Da), we conclude that subunit 7 is MSS1.