Zinc-Dependent Oligomerization of Trigger Factor Chaperone.

trigger factor (TF) is a zinc-dependent molecular chaperone whose folding-arrest activity is regulated by Zn. However, little is known about the mechanism of zinc-dependent regulation of the TF activity. Here we exploit in vitro biophysical experiments to investigate zinc-binding, the oligomeric state, the secondary structure, and the thermal stability of TF in the absence and presence of Zn. The data show that full-length TF binds Zn, but the isolated domains and tandem domains of TF do not bind to Zn. Furthermore, circular dichroism (CD) and nuclear magnetic resonance (NMR) spectra suggested that Zn-binding induces the partial structural changes of TF, and size exclusion chromatography-multi-angle light scattering (SEC-MALS) showed that Zn promotes TF oligomerization. Given the previous work showing that the activity regulation of trigger factor is accompanied by oligomerization, the data suggest that TF exploits zinc ions to induce the structural change coupled with the oligomerization to assemble the client-binding site, thereby effectively preventing proteins from misfolding in the thermal environment.