August Krogh Institute, University of Copenhagen, Denmark.
Human proteasomes consist of 14 major subunits which can be resolved by two-dimensional polyacrylamide gel electrophoresis. Tryptic peptides from the subunits were sequenced. This allowed identification of all proteins in two-dimensional electrophoresis gels with proteasome subunits whose sequences are known from cDNA. The results also precisely define the specificity of a panel of subunit-specific monoclonal antibodies. A new proteasome subunit (Z) was discovered. In contrast, the putative subunit MECL-1 could not be detected in human placenta proteasomes.