Toggle switch residues control allosteric transitions in bacterial adhesins by participating in a concerted repacking of the protein core
| Autor: | Hovhannes Avagyan, Rachel E. Klevit, Laura A. Carlucci, Evgeni V. Sokurenko, Benjamin Basanta, Dagmara I. Kisiela, Angelo Ramos, Wendy E. Thomas, Ronald E. Stenkamp, Pearl Magala, Veronika Tchesnokova, Vladimir Yarov-Yarovoy, Anahit Hovhannisyan, Gianluca Interlandi |
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| Přispěvatelé: | Francetic, Olivera |
| Rok vydání: | 2021 |
| Předmět: |
Models
Molecular Hydrolases Mannose Catch bond Pathology and Laboratory Medicine Spectrum analysis techniques Biochemistry Epitope Bacterial Adhesion chemistry.chemical_compound 0302 clinical medicine Electronics Engineering Models Microbial Physiology Lectins Medicine and Health Sciences Bacterial Physiology Amino Acids Enzyme-Linked Immunoassays Biology (General) Alanine 0303 health sciences Adhesins Escherichia coli Chemistry Organic Compounds Mannose binding Bacterial Adhesins Enzymes Medical Microbiology Physical Sciences Engineering and Technology Fimbriae Proteins Cellular Structures and Organelles Pathogens Research Article Protein Binding Steric effects Pathogen Motility Stereochemistry Virulence Factors Nucleases QH301-705.5 Allosteric regulation Immunology Microbiology Fimbriae 03 medical and health sciences Ribonucleases NMR spectroscopy Virology DNA-binding proteins Genetics Toggle Switches Escherichia coli Adhesins Bacterial Immunoassays Molecular Biology 030304 developmental biology Organic Chemistry Chemical Compounds Biology and Life Sciences Proteins Molecular Bacteriology Cell Biology RC581-607 Bacterial adhesin Research and analysis methods Pili and Fimbriae Aliphatic Amino Acids Fimbriae Bacterial Enzymology Immunologic Techniques Parasitology Generic health relevance Immunologic diseases. Allergy 030217 neurology & neurosurgery |
| Zdroj: | PLoS pathogens, vol 17, iss 4 PLoS Pathogens, Vol 17, Iss 4, p e1009440 (2021) PLoS Pathogens |
| Popis: | Critical molecular events that control conformational transitions in most allosteric proteins are ill-defined. The mannose-specific FimH protein of Escherichia coli is a prototypic bacterial adhesin that switches from an ‘inactive’ low-affinity state (LAS) to an ‘active’ high-affinity state (HAS) conformation allosterically upon mannose binding and mediates shear-dependent catch bond adhesion. Here we identify a novel type of antibody that acts as a kinetic trap and prevents the transition between conformations in both directions. Disruption of the allosteric transitions significantly slows FimH’s ability to associate with mannose and blocks bacterial adhesion under dynamic conditions. FimH residues critical for antibody binding form a compact epitope that is located away from the mannose-binding pocket and is structurally conserved in both states. A larger antibody-FimH contact area is identified by NMR and contains residues Leu-34 and Val-35 that move between core-buried and surface-exposed orientations in opposing directions during the transition. Replacement of Leu-34 with a charged glutamic acid stabilizes FimH in the LAS conformation and replacement of Val-35 with glutamic acid traps FimH in the HAS conformation. The antibody is unable to trap the conformations if Leu-34 and Val-35 are replaced with a less bulky alanine. We propose that these residues act as molecular toggle switches and that the bound antibody imposes a steric block to their reorientation in either direction, thereby restricting concerted repacking of side chains that must occur to enable the conformational transition. Residues homologous to the FimH toggle switches are highly conserved across a diverse family of fimbrial adhesins. Replacement of predicted switch residues reveals that another E. coli adhesin, galactose-specific FmlH, is allosteric and can shift from an inactive to an active state. Our study shows that allosteric transitions in bacterial adhesins depend on toggle switch residues and that an antibody that blocks the switch effectively disables adhesive protein function. Author summary To bind their ligands, allosteric proteins shift between ‘inactive’ and ‘active’ states, but molecular details of the conformational changes during the transition are often unclear. We describe a monoclonal antibody against the mannose-specific bacterial adhesin, FimH, that blocks the conformational transition in both directions. The antibody-trapped LAS and HAS conformations of FimH are unable to mediate bacterial adhesion under dynamic shear conditions. We propose that the conformational trapping involves a steric block of the core-to-surface switching of certain residues which is critical for the allosteric transitions. Furthermore, we demonstrate that the allosteric switches are structurally and functionally conserved across a broad spectrum of bacterial fimbrial adhesins. |
| Databáze: | OpenAIRE |
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