Julian Deeng, Kwok-Yan Chan, Eli O. van der Sluis, Lukas Bischoff, Otto
Berninghausen, Wei Han, James Gumbart, Klaus Schulten, Birgitta Beatrix, and
Roland Beckmann.
Dynamic behavior of trigger factor on the ribosome.
Journal of Molecular Biology, 428:3588-3602, 2016.
DEEN2016
Trigger factor is the only ribosome-associated chaperone in bacteria. It interacts
with hydrophobic segments in nascent chains 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-EM structures of TF bound to
ribosomes translating an mRNA coding for a known TF substrate from E. coli of
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 nascent chain is
extended. Molecular dynamics simulations agree with these data and offer a
molecular basis for these observations.
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