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

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Santiago-Frangos, Andrew 
Fröhlich, Kathrin S 
Jeliazkov, Jeliazko R 
Małecka, Ewelina M 

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.

Caulobacter, Hfq, RNA–protein interaction, natively unstructured protein, sRNA, Bacterial Proteins, Caulobacter crescentus, Crystallography, X-Ray, Host Factor 1 Protein, Models, Molecular, Molecular Chaperones, Protein Binding, RNA, Bacterial, RNA, Messenger, RNA, Small Untranslated
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Proc Natl Acad Sci U S A
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Proceedings of the National Academy of Sciences
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Wellcome Trust (200873/Z/16/Z)
SWH and BL are funded by the Wellcome Trust (200873/Z/16/Z). This work was also supported by the NIH (R01 GM120425 to SW, F31 GM123616 to JRJ, and R01 GM078221 to JJG). KF acknowledges funding by the LMU Mentoring program of the LMU Faculty of Biology.