The N-terminal domain of RfaH plays an active role in protein fold-switching

PLoS Comput Biol. 2021 Sep 3;17(9):e1008882. doi: 10.1371/journal.pcbi.1008882. eCollection 2021 Sep.

Abstract

The bacterial elongation factor RfaH promotes the expression of virulence factors by specifically binding to RNA polymerases (RNAP) paused at a DNA signal. This behavior is unlike that of its paralog NusG, the major representative of the protein family to which RfaH belongs. Both proteins have an N-terminal domain (NTD) bearing an RNAP binding site, yet NusG C-terminal domain (CTD) is folded as a β-barrel while RfaH CTD is forming an α-hairpin blocking such site. Upon recognition of the specific DNA exposed by RNAP, RfaH is activated via interdomain dissociation and complete CTD structural rearrangement into a β-barrel structurally identical to NusG CTD. Although RfaH transformation has been extensively characterized computationally, little attention has been given to the role of the NTD in the fold-switching process, as its structure remains unchanged. Here, we used Associative Water-mediated Structure and Energy Model (AWSEM) molecular dynamics to characterize the transformation of RfaH, spotlighting the sequence-dependent effects of NTD on CTD fold stabilization. Umbrella sampling simulations guided by native contacts recapitulate the thermodynamic equilibrium experimentally observed for RfaH and its isolated CTD. Temperature refolding simulations of full-length RfaH show a high success towards α-folded CTD, whereas the NTD interferes with βCTD folding, becoming trapped in a β-barrel intermediate. Meanwhile, NusG CTD refolding is unaffected by the presence of RfaH NTD, showing that these NTD-CTD interactions are encoded in RfaH sequence. Altogether, these results suggest that the NTD of RfaH favors the α-folded RfaH by specifically orienting the αCTD upon interdomain binding and by favoring β-barrel rupture into an intermediate from which fold-switching proceeds.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Escherichia coli / chemistry
  • Escherichia coli Proteins / chemistry*
  • Molecular Dynamics Simulation
  • Nuclear Magnetic Resonance, Biomolecular
  • Peptide Elongation Factors / chemistry*
  • Protein Domains
  • Protein Folding*
  • Trans-Activators / chemistry*

Substances

  • Escherichia coli Proteins
  • Peptide Elongation Factors
  • RfaH protein, E coli
  • Trans-Activators

Grants and funding

This research was funded by the National Agency for Research and Development (ANID) FONDECYT Regular Grant 1201684 (to CARS) and ANID Millennium Science Initiative Program ICN17_022. PGD was supported by ANID Doctoral Scholarship 21181705. EAR has a research grant from Agencia Nacional de Promoción Científica y Tecnológica (PICT 2016-0014). Powered@NLHPC: This research was partially supported by the supercomputing infrastructure of the NLHPC (ECM-02). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.