The dynamic dimer structure of the chaperone Trigger Factor

Leonor Morgado,Timothy Sharpe,Björn M Burmann,Sebastian Hiller,Adam Mazur

doi:10.1038/s41467-017-02196-7

Leonor Morgado, Timothy Sharpe + Show 3 more

Open Access

https://doi.org/10.1038/s41467-017-02196-7

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Abstract

The chaperone Trigger Factor (TF) from Escherichia coli forms a dimer at cellular concentrations. While the monomer structure of TF is well known, the spatial arrangement of this dimeric chaperone storage form has remained unclear. Here, we determine its structure by a combination of high-resolution NMR spectroscopy and biophysical methods. TF forms a symmetric head-to-tail dimer, where the ribosome binding domain is in contact with the substrate binding domain, while the peptidyl-prolyl isomerase domain contributes only slightly to the dimer affinity. The dimer structure is highly dynamic, with the two ribosome binding domains populating a conformational ensemble in the center. These dynamics result from intermolecular in trans interactions of the TF client-binding site with the ribosome binding domain, which is conformationally frustrated in the absence of the ribosome. The avidity in the dimer structure explains how the dimeric state of TF can be monomerized also by weakly interacting clients.

Highlights

The chaperone Trigger Factor (TF) from Escherichia coli forms a dimer at cellular concentrations
Since the domain folds are preserved in all available TF crystal structures, we decided to probe the integrity of individual folds in aqueous solution by calculating the secondary chemical shifts of the ribosome-binding domain (RBD), substratebinding domain (SBD), and SBD–peptidyl-prolyl isomerase domain (PPD) constructs and comparing them to the available TF crystal structure (PDB 1W26; Fig. 1c)
The experiments presented in this work have resolved the longstanding question about the spatial arrangement of the dimeric form of E. coli TF in solution

Summary

Introduction

The chaperone Trigger Factor (TF) from Escherichia coli forms a dimer at cellular concentrations. While the monomer structure of TF is well known, the spatial arrangement of this dimeric chaperone storage form has remained unclear. Several atomic resolution structures of TF from different organisms (E. coli, Thermotoga maritima, Vibrio cholerae, Deinococcus radiodurans, and Mycoplasma genitalium) are available for the full-length protein[8, 16, 17], as well as for its individual domains[10, 11, 18, 19], in complex with the ribosome[8, 20] or in complex with substrates[17, 21]. The T. maritima structure was determined both in apo form (PDB 3GU0) and in complex with the ribosomal protein S7 (PDB 3GTY), resulting in different arrangements[17]. Different models and suggestions are available for the structure of the TF dimer

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