ATP-DEPENDENT PROTEIN REFOLDING ACTIVITY IN RETICULOCYTE LYSATE - EVIDENCE FOR THE PARTICIPATION OF DIFFERENT CHAPERONE COMPONENTS

The protein folding capacity of rabbit reticulocyte cytosol was analyz ed using the renaturation of firefly luciferase as a sensitive assay. In the absence of ATP, the aggregation of denatured luciferase diluted into reticulocyte lysate was prevented. Chaperone-stabilized lucifera se was detected in high molecular weight complexes overlapping the dis tributions of Hsc70, Hsp90 and the chaperonin TRiC on gel filtration c olumns. The readdition of unfractionated cytosol and Mg-ATP was requir ed tor the efficient folding of these forms of luciferase to the activ e enzyme. We conclude that protein folding in the eukaryotic cytosol d epends on the functional cooperation of different chaperone activities and cofactors in a complex, ATP-dependent process.