Preprints
https://doi.org/10.5194/mr-2021-9
https://doi.org/10.5194/mr-2021-9

  25 Jan 2021

25 Jan 2021

Review status: this preprint is currently under review for the journal MR.

Structural polymorphism and substrate promiscuity of a ribosome-associated molecular chaperone

Chih-Ting Huang1, Yei-Chen Lai2, Szu-Yun Chen1, Meng-Ru Ho1, Yun-Wei Chiang2, and Shang-Te Danny Hsu1,3 Chih-Ting Huang et al.
  • 1Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan
  • 2Department of Chemistry, National Tsing Hua University, Hsichu 30013, Taiwan
  • 3Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan

Abstract. Trigger factor (TF) is a highly conserved multi-domain molecular chaperone that exerts its chaperone activity at the ribosomal tunnel exit from which newly synthesized nascent chains emerge. TF also displays promiscuous substrate binding for a large number of cytosolic proteins independent of ribosome binding. We asked how TF recognizes a variety of substrates while existing in a monomer-dimer equilibrium. Paramagnetic NMR, electron spin resonance spectroscopy and chemical crosslink show that dimeric TF displays a high degree of structural polymorphism in solution. A series of peptides has been generated to quantify their TF binding affinities in relation with their sequence compositions. The results confirmed a previous predication that TF preferentially binds to peptide fragments that are rich in aromatic and positively charged amino acids. NMR paramagnetic relaxation enhancement analysis showed that TF utilizes multiple binding sites, located in the chaperone domain and part of the prolyl trans/cis isomerisation domain, to interact with these peptides. Dimerization of TF effectively sequesters most of substrate binding sites, which are expected to become accessible upon binding to the ribosome as a monomer. As TF lacks ATPase activity, which is commonly used to trigger conformational changes within molecular chaperones in action, the ribosome-binding-associated disassembly and conformational rearrangements may be the underlying regulatory mechanism of its chaperone activity.

Chih-Ting Huang et al.

Status: open (until 15 Mar 2021)

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  • RC1: 'Comment on mr-2021-9', Anonymous Referee #1, 11 Feb 2021 reply

Chih-Ting Huang et al.

Chih-Ting Huang et al.

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Short summary
Trigger factor (TF) is a conserved bacterial molecular chaperone that exists in a monomer-dimer equilibrium in solution. It binds to the ribosome as a monomer to facilitate folding of nascent polypeptide chains. We showed that dimeric TF exhibits distinct domain dynamics and conformational polymorphism, and that TF contains multiple substrate binding sites that are only accessible in its monomeric form. The equilibrium of TF in different oligomeric states may serve as an regulatory mechanism.