Sem1 links proteasome stability and specificity to multicellular development
Fig 2
Accumulation of 20S proteasome complexes in Δsem1.
(A) Electron micrographs of negatively stained proteasome complexes derived from fungal cell extracts. The total numbers of proteasome complexes and the respective complexes observed (%) in Δsem1, wildtype (sem1) or complemented (Δsem1::sem1-gfp) strains are indicated. (B) Δsem1 proteasomes showed similar peptidase activities regardless to the presence or absence of ATP and KCl. Activities were measured in assay buffer containing 0.125mM ATP, 10mM KCl and 2.5μM of the proteasome inhibitor MG132. The assay buffer also contained 12.5 mM Tris HCl pH = 7.5 +1.25 mM MgCl2 +0.25 mM DTT+0.0125 mg/ml BSA. Blue, red and green curves represent peptidase activity of the indicated strains in the presence of ATP+KCl (26S activity), in the absence of ATP and KCl (-ATP–KCl, 20S) and in the presence of MG132 (proteasome inhibitor).