Signal Transduction at the Domain Interface of Prokaryotic Pentameric Ligand-Gated Ion Channels
| Autor: | Raimund Dutzler, Carlo Bertozzi, Sibylle Engeler, Iwan Zimmermann, Ricarda J. C. Hilf |
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| Přispěvatelé: | University of Zurich, Dutzler, Raimund |
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Nicotinic Acetylcholine Receptors Xenopus Biochemistry Protein structure Animal Cells 2400 General Immunology and Microbiology Macromolecular Structure Analysis Biology (General) Amino Acids Crystallography Alanine Organic Compounds General Neuroscience Physics 2800 General Neuroscience Animal Models Condensed Matter Physics Transport protein Chemistry OVA Physical Sciences Vertebrates Crystal Structure Ligand-gated ion channel Frogs Cellular Types General Agricultural and Biological Sciences Research Article Signal Transduction Protein Structure Proline Transmembrane Receptors QH301-705.5 GLIC 610 Medicine & health 1100 General Agricultural and Biological Sciences Biology Research and Analysis Methods General Biochemistry Genetics and Molecular Biology Amphibians 03 medical and health sciences Model Organisms 1300 General Biochemistry Genetics and Molecular Biology 10019 Department of Biochemistry Genetics Solid State Physics Point Mutation Animals Molecular Biology Ion channel General Immunology and Microbiology Organic Chemistry Chemical Compounds Organisms Biology and Life Sciences Proteins Isothermal titration calorimetry Cyclic Amino Acids Cell Biology A-site 030104 developmental biology Germ Cells Membrane protein Aliphatic Amino Acids Acetylcholine Receptors Mutation Biophysics Oocytes 570 Life sciences biology |
| Zdroj: | PLoS Biology PLoS Biology, Vol 14, Iss 3, p e1002393 (2016) |
| ISSN: | 1545-7885 1544-9173 |
| Popis: | Pentameric ligand-gated ion channels are activated by the binding of agonists to a site distant from the ion conduction path. These membrane proteins consist of distinct ligand-binding and pore domains that interact via an extended interface. Here, we have investigated the role of residues at this interface for channel activation to define critical interactions that couple conformational changes between the two structural units. By characterizing point mutants of the prokaryotic channels ELIC and GLIC by electrophysiology, X-ray crystallography and isothermal titration calorimetry, we have identified conserved residues that, upon mutation, apparently prevent activation but not ligand binding. The positions of nonactivating mutants cluster at a loop within the extracellular domain connecting β-strands 6 and 7 and at a loop joining the pore-forming helix M2 with M3 where they contribute to a densely packed core of the protein. An ionic interaction in the extracellular domain between the turn connecting β-strands 1 and 2 and a residue at the end of β-strand 10 stabilizes a state of the receptor with high affinity for agonists, whereas contacts of this turn to a conserved proline residue in the M2-M3 loop appear to be less important than previously anticipated. When mapping residues with strong functional phenotype on different channel structures, mutual distances are closer in conducting than in nonconducting conformations, consistent with a potential role of contacts in the stabilization of the open state. Our study has revealed a pattern of interactions that are crucial for the relay of conformational changes from the extracellular domain to the pore region of prokaryotic pentameric ligand-gated ion channels. Due to the strong conservation of the interface, these results are relevant for the entire family. Interacting residues at the interface between the extracellular domain and the pore of prokaryotic pentameric ligand-gated ion channels play an important role in the transduction of conformational changes that lead to channel activation. Author Summary The pentameric ligand-gated ion channels constitute a large family of membrane proteins that are expressed in animals and certain bacteria. Their molecular architecture and function is conserved throughout the family. In mammals, they operate as receptors of the neurotransmitters acetylcholine, serotonin, GABA, and glycine and play a key role in electrical signal transduction at chemical synapses. These receptors are called ionotropic because they open a selective ion conduction path across the membrane upon binding of the neurotransmitters to a site that is exposed to the extracellular medium. Ligand binding promotes a conformational change in the extracellular domain that is transmitted over more than 50 Å to the pore domain. Due to this long-range effect, pentameric ligand-gated ion channels have become important model systems for the study of allosteric processes, a mechanism that is of large importance for biology and entails the regulation of a protein activity by an effector that binds to a distant domain. In the present study, we investigated the role that residues in the contact region between the ligand-binding and the pore domains of two bacterial pentameric ligand-gated ion channels of known structure have in the transduction of conformational changes. Our study shows that single mutations severely influence the functional properties, with certain mutations preventing activation. The results underline the importance of highly conserved residues in the domain interface for the transmission of allosteric signals and thus likely apply also to other family members. |
| Databáze: | OpenAIRE |
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