FIG. 3.

UBP-t1 and UBP-t2 have deubiquitinating-enzyme activities. Enzymatic activities toward ¹²⁵I-diubiquitin (Di-Ub) joined in a peptide bond and ¹²⁵I-triubiquitin polymer (Tri-Ub) linked via lysine 48 isopeptide bonds were measured in lysates prepared from E. coli cells expressing either UBP-t1 or UBP-t2. Reaction products were separated by SDS-PAGE and detected by autoradiography. An equivalent volume of bacterial lysate not expressing UBP-t1 or UBP-t2 was used as the negative control.