Dynamic Behavior of Trigger Factor on the Ribosome.
Deeng, J., Chan, K.Y., Van Der Sluis, E.O., Berninghausen, O., Han, W., Gumbart, J., Schulten, K., Beatrix, B., Beckmann, R.(2016) J Mol Biol 428: 3588
- PubMed: 27320387 
- DOI: https://doi.org/10.1016/j.jmb.2016.06.007
- Primary Citation of Related Structures:  
4URD - PubMed Abstract: 
Trigger factor (TF) is the only ribosome-associated chaperone in bacteria. It interacts with hydrophobic segments in nascent chain (NCs) as they emerge from the ribosome. TF binds via its N-terminal ribosome-binding domain (RBD) mainly to ribosomal protein uL23 at the tunnel exit on the large ribosomal subunit. Whereas earlier structural data suggested that TF binds as a rigid molecule to the ribosome, recent comparisons of structural data on substrate-bound, ribosome-bound, and TF in solution from different species suggest that this chaperone is a rather flexible molecule. Here, we present two cryo-electron microscopy structures of TF bound to ribosomes translating an mRNA coding for a known TF substrate from Escherichia coli of a different length. The structures reveal distinct degrees of flexibility for the different TF domains, a conformational rearrangement of the RBD upon ribosome binding, and an increase in rigidity within TF when the NC is extended. Molecular dynamics simulations agree with these data and offer a molecular basis for these observations.
Organizational Affiliation: 
Gene Center Munich and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Straße 25, Munich 81377, Germany.