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Proc Natl Acad Sci U S A. 2019 May 28;116(22):10978-10987. doi: 10.1073/pnas.1814428116. Epub 2019 May 10.

Caulobacter crescentus Hfq structure reveals a conserved mechanism of RNA annealing regulation.

Author information

1
Cell, Molecular and Developmental Biology and Biophysics Program, Johns Hopkins University, Baltimore, MD 21218.
2
Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218.
3
Department of Biology I, Microbiology, Ludwig Maximilian University Munich, 82152 Martinsried, Germany.
4
Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD 21218.
5
Department of Biology I, Plant Molecular Biology, Ludwig Maximilian University Munich, 82152 Martinsried, Germany.
6
Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218.
7
Department of Biochemistry, University of Cambridge, CB2 1GA Cambridge, United Kingdom bfl20@cam.ac.uk swoodson@jhu.edu swh32@cam.ac.uk.
8
Cell, Molecular and Developmental Biology and Biophysics Program, Johns Hopkins University, Baltimore, MD 21218; bfl20@cam.ac.uk swoodson@jhu.edu swh32@cam.ac.uk.

Abstract

We have solved the X-ray crystal structure of the RNA chaperone protein Hfq from the alpha-proteobacterium Caulobacter crescentus to 2.15-Å resolution, resolving the conserved core of the protein and the entire C-terminal domain (CTD). The structure reveals that the CTD of neighboring hexamers pack in crystal contacts, and that the acidic residues at the C-terminal tip of the protein interact with positive residues on the rim of Hfq, as has been recently proposed for a mechanism of modulating RNA binding. De novo computational models predict a similar docking of the acidic tip residues against the core of Hfq. We also show that C. crescentus Hfq has sRNA binding and RNA annealing activities and is capable of facilitating the annealing of certain Escherichia coli sRNA:mRNA pairs in vivo. Finally, we describe how the Hfq CTD and its acidic tip residues provide a mechanism to modulate annealing activity and substrate specificity in various bacteria.

KEYWORDS:

Caulobacter; Hfq; RNA–protein interaction; natively unstructured protein; sRNA

PMID:
31076551
PMCID:
PMC6561178
DOI:
10.1073/pnas.1814428116
[Indexed for MEDLINE]
Free PMC Article

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