Hsp70 chaperones assist in a large variety of protein-folding processes in the
cell. Crucial for these activities is the regulation of Hsp70 by Hsp40
cochaperones. DnaJ, the bacterial homologue of Hsp40, stimulates ATP
hydrolysis by DnaK (Hsp70) and thus mediates capture of substrate protein, but
is also known to possess chaperone activity of its own. The first structure of
a complete functional dimeric DnaJ was determined and the mobility of its
individual domains in solution was investigated. Crystal structures of the
complete molecular cochaperone DnaJ from Thermus thermophilus comprising the
J, GF and C-terminal domains and of the J and GF domains alone showed an
ordered GF domain interacting with the J domain. Structure-based EPR spin-
labelling studies as well as cross-linking results showed the existence of
multiple states of DnaJ in solution with different arrangements of the various
domains, which has implications for the function of DnaJ.1\. Auflag
