Verification of the interdomain contact site in the inactive monomer, and the domain‐swapped fold in the active dimer of Hsp33 in solution

Abstract

a b s t r a c tUpon dimerization by oxidation, Hsp33 functions as a molecular chaperone in prokaryotes. Previously published structures of both the inactive and active species are of doubtful relevance to the solution conformations since the inactive (reduced) crystal structure was dimeric, while the active (oxidized) species was crystallized with a truncation of its regulation domain. The interdomain contact site of the inactive monomer, identified in this work, is consistent with that previously observed in the reduced dimer crystal. In contrast, fluorescence quenching of the active dimer contradicted the results expected from the domain-swapped fold observed in the truncated dimer crystal. The results of this study provide important new information concerning controversial issues in the activation process of Hsp33.

Chaperones and chaperone–substrate complexes: Dynamic playgrounds for NMR spectroscopists

“…Upon oxidative stress the cysteines form disulfides and detach from the substrate-binding site, and the secondary structure within the C-terminus is lost, leading to a partly active monomer. These partly active monomers quickly associate together to give the fully active Hsp33 dimer, forming a swapped dimer with an extended substrate-binding site [343][344][345]. Subsequent analysis of the structure of the C-terminal in the Zn 2+ -state revealed a unique fold of three -helices surrounding two -strands [346].…”

Molecular Effects of Elongation Factor Ts and Trigger Factor on the Unfolding and Aggregation of Elongation Factor Tu Induced by the Prokaryotic Molecular Chaperone Hsp33

“…Consequently, this partially-unfolded Hsp33 functions as a holding chaperone that binds to unfolding intermediates of client proteins to prevent further progression of misfolding and promote native folding [ 17 , 18 , 19 ]. In addition, dimer and high-order oligomer formation of activated Hsp33 enhances its chaperone activity [ 16 , 20 , 21 ].…”