Single-Molecule Analyses on the Dynamics of Heat Shock Protein 104 (Hsp104) and Protein Aggregates [Protein Structure and Folding]

January 29th, 2015 by Okuda, M., Niwa, T., Taguchi, H.

Hsp104 solubilizes protein aggregates in cooperation with Hsp70/40. Although the framework of the disaggregase function has been elucidated, the actual process of aggregate solubilization by Hsp104-Hsp70/40 remains poorly understood. Here, we have developed several methods to investigate the functions of Hsp104 and Hsp70/40 from Saccharomyces cerevisiae, at single-molecule levels. The single-molecule methods, which provide the size distribution of the aggregates, revealed that Hsp70/40 prevented the formation of large aggregates from small aggregates, and that the solubilization of the small aggregates required both Hsp104 and Hsp70/40. We directly visualized the individual association-dissociation dynamics of Hsp104 on immobilized aggregates, and found that the lifetimes of the Hsp104-aggregate complex are divided into two groups: short (~4 s) and long (~30 s). Hsp70/40 stimulated the association of Hsp104 with aggregates, and increased the duration of this association. The single-molecule data provide novel insights into the functional mechanism of the Hsp104 disaggregation machine.