||Bacteria Escherichia coli
||Sharma SK, De los Rios P, Christen P, Lustig A, Goloubinoff P. The kinetic parameters and energy cost of the Hsp70 chaperone as a polypeptide unfoldase. Nat Chem Biol. 2010 Dec6(12):914-20. doi: 10.1038/nchembio.455. abstractPubMed ID20953191
||P.914 right column 2nd paragraph: "Here [investigators] clarified the mechanistic subprocesses of the Escherichia coli version of the Hsp70-Hsp40-NEF chaperone system, the DnaK-DnaJ-GrpE system, by using a preformed and well-characterized misfolded substrate. [They] denatured a firefly luciferase mutant by a freeze-thaw treatment and isolated a near-homogenous population of stable, misfolded compact inactive monomers. The unique qualities of this chaperone substrate allowed for the first time the measuring of the rates of the various steps leading from a stable inactive misfolded state to a stable, native, enzymatically active refolded state. This permitted [them] to correlate rates of ATP consumption with rates of refolding to the native state. The data showed that bacterial Hsp70, DnaK, uses the energy of ATP to convert misfolded substrates into unfolded intermediates that, upon release from the chaperone, can spontaneously refold to their native state."
||Abstract: "Under the in vitro conditions used, one Hsp70 molecule consumed five ATPs to effectively unfold a single misfolded protein into an intermediate that, upon chaperone dissociation, spontaneously refolded to the native state, a process with an ATP cost a thousand times lower than expected for protein degradation and resynthesis."