Bar plots depicting the quantification of chymotrypsin-like (CT-L) activity from native gels calculated for doubly capped (30S) or singly capped (26S) proteasomes. n >=5 per sample group; error bars indicate standard error of the mean. * p < 0.05, ** p < 0.005, *** p=0.0001, **** p < 0.001, one-way ANOVA, Holm-Sidak's multiple comparison test. For each sample group, the mean value of activity in young samples (5 wph) was set to 100%. 