Single-molecule study of the dynamics of the molecular chaperone Hsp70 during the functional cycle.

The 70-kDa heat shock protein, Hsp70, is a key chaperone involved in cellular protein homeostasis. The structure of the Hsp70 protein family is highly conserved, including a nucleotide-binding domain (NBD) and a substrate-binding domain (SBD). ATP binding and hydrolysis in the NBD of Hsp70 regulates the binding and release of substrates in the SBD via interdomain allosteric communication. Growing evidence shows that the conformational dynamics of Hsp70 are crucial for its function, which are difficult to probe by traditional bulk-based methods. Single-molecule techniques are emerging as powerful tools to explore the dynamics of proteins that are obscured in bulk measurements. In this review, we summarize recent progress in the study of the molecular dynamics of Hsp70 and its interactions with cochaperones and substrates using single-molecule fluorescence spectroscopy and single-molecule force spectroscopy. We discuss how the application of single-molecule techniques facilitates a deeper understanding of the mechanistic details of the chaperone functions of Hsp70.