Fig. 8.

Thermostability assay. (a) SIRT1^CAT was incubated alone and in the presence of SUMO-CTR or a non-interacting SUMO-CTR^{Y650D, I651D} mutant at the indicated temperatures for one hour and pelleted by centrifugation. Pellet and supernatant fractions were visualized by SDS-PAGE, followed by Coomassie brilliant blue staining. Molecular mass standards and the positions of the proteins are indicated. (b) Deacetylase activity of SIRT1^CAT and the SIRT1^CAT•CTR heterodimer under normal conditions (red) and following incubation at 37 °C for approximately 2 hours prior to the assay (blue). Activity was determined in a fluorescence-based assay and normalized against wild-type SIRT1^CAT activity. Each data point represents the mean of at least three independent measurements. Error bars represent standard deviations. The loss of deacetylase activity is attributed to the aggregation of the catalytic domain.