Functional role of the type 1 pilus rod structure in mediating host-pathogen interactions
Abstract
Uropathogenic E. coli (UPEC), which cause urinary tract infections (UTI), utilize type 1 pili, a chaperone usher pathway (CUP) pilus, to cause UTI and colonize the gut. The pilus rod, comprised of repeating FimA subunits, provides a structural scaffold for displaying the tip adhesin, FimH. We solved the 4.2 Å resolution structure of the type 1 pilus rod using cryo-electron microscopy. Residues forming the interactive surfaces that determine the mechanical properties of the rod were maintained by selection based on a global alignment of fimA sequences. We identified mutations that did not alter pilus production in vitro but reduced the force required to unwind the rod. UPEC expressing these mutant pili were significantly attenuated in bladder infection and intestinal colonization in mice. This study elucidates an unappreciated functional role for the molecular spring-like property of type 1 pilus rods in host-pathogen interactions and carries important implications for other pilus-mediated diseases.
Data availability
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Bacteria Genome sequencing and assemblyPublicly available at the NCBI BioProject Database (accession PRJNA269984).
Article and author information
Author details
Funding
National Institutes of Health (GM122510)
- Edward H Egelman
Washington University School of Medicine (Monsanto Excellence Fund Graduate Fellowship)
- Henry Louis Schreiber
National Institutes of Health (AI048689)
- Scott Hultgren
National Institutes of Health (DK064540)
- Scott Hultgren
National Institutes of Health (1F31DK107057)
- Caitlin N Spaulding
National Institutes of Health (DK101171-02)
- Matt S Conover
Svenska Forskningsrådet Formas (621-2013-5379)
- Magnus Andersson
Agence Nationale de la Recherche (ANR-14-CE09-0004)
- Olivera Francetic
Paris Pasteur University (Graduate Research Fellowship)
- Areli Luna-Rico
Washington University School of Medicine (Lucille P. Markey Pathway for Pathobiology)
- Henry Louis Schreiber
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: The Washington University Animal Studies Committee approved all procedures used for the mouse experiments described in the present study (Protocol Application Number 20150226). Overall care of the animals was consistent with The Guide for the Care and Use of Laboratory Animals from the National Research Council and the USDA Animal Care Resource Guide. Every effort was made to minimize suffering.
Reviewing Editor
- Michael S Gilmore, Harvard Medical School, United States
Publication history
- Received: August 31, 2017
- Accepted: January 12, 2018
- Accepted Manuscript published: January 18, 2018 (version 1)
- Version of Record published: February 5, 2018 (version 2)
Copyright
© 2018, Spaulding et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Further reading
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- Biochemistry and Chemical Biology
- Structural Biology and Molecular Biophysics
Mycobacterium tuberculosis adenylyl cyclase (AC) Rv1625c / Cya is an evolutionary ancestor of the mammalian membrane ACs and a model system for studies of their structure and function. Although the vital role of ACs in cellular signaling is well established, the function of their transmembrane (TM) regions remains unknown. Here we describe the cryo-EM structure of Cya bound to a stabilizing nanobody at 3.6 Å resolution. The TM helices 1-5 form a structurally conserved domain that facilitates the assembly of the helical and catalytic domains. The TM region contains discrete pockets accessible from the extracellular and cytosolic side of the membrane. Neutralization of the negatively charged extracellular pocket Ex1 destabilizes the cytosolic helical domain and reduces the catalytic activity of the enzyme. The TM domain acts as a functional component of Cya, guiding the assembly of the catalytic domain and providing the means for direct regulation of catalytic activity in response to extracellular ligands.
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- Structural Biology and Molecular Biophysics
To clarify the determinants of agonist efficacy in pentameric ligand-gated ion channels we examined a new compound, aminomethanesulfonic acid (AMS), a molecule intermediate in structure between glycine and taurine. Despite wide availability, to date there are no reports of AMS action on glycine receptors, perhaps because AMS is unstable at physiological pH. Here we show that at pH 5, AMS is an efficacious agonist, eliciting in zebrafish α1 glycine receptors a maximum single channel open probability of 0.85, much greater than that of β-alanine (0.54) or taurine (0.12), and second only to that of glycine itself (0.96). Thermodynamic cycle analysis of the efficacy of these closely related agonists shows supra-additive interaction between changes in the length of the agonist molecule and the size of the anionic moiety. Single particle cryo-EM structures of AMS-bound glycine receptors show that the AMS-bound agonist pocket is as compact as with glycine, and three-dimensional classification demonstrates that the channel populates the open and the desensitized states, like glycine, but not the closed intermediate state associated with the weaker partial agonists, β-alanine and taurine. Because AMS is on the cusp between full and partial agonists, it provides a new tool to help us understand agonist action in the pentameric superfamily of ligand-gated ion channels.