1
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Renart ML, Giudici AM, González-Ros JM, Poveda JA. Steady-state and time-resolved fluorescent methodologies to characterize the conformational landscape of the selectivity filter of K + channels. Methods 2024; 225:89-99. [PMID: 38508347 DOI: 10.1016/j.ymeth.2024.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 02/02/2024] [Accepted: 02/23/2024] [Indexed: 03/22/2024] Open
Abstract
A variety of equilibrium and non-equilibrium methods have been used in a multidisciplinary approach to study the conformational landscape associated with the binding of different cations to the pore of potassium channels. These binding processes, and the conformational changes resulting therefrom, modulate the functional properties of such integral membrane properties, revealing these permeant and blocking cations as true effectors of such integral membrane proteins. KcsA, a prototypic K+ channel from Streptomyces lividans, has been extensively characterized in this regard. Here, we revise several fluorescence-based approaches to monitor cation binding under different experimental conditions in diluted samples, analyzing the advantages and disadvantages of each approach. These studies have contributed to explain the selectivity, conduction, and inactivation properties of K+ channels at the molecular level, together with the allosteric communication between the two gates that control the ion channel flux, and how they are modulated by lipids.
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Affiliation(s)
- María Lourdes Renart
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain.
| | - Ana Marcela Giudici
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain.
| | - José M González-Ros
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain.
| | - José A Poveda
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain.
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2
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Coutinho A, Poveda JA, Renart ML. Conformational Dynamic Studies of Prokaryotic Potassium Channels Explored by Homo-FRET Methodologies. Methods Mol Biol 2024; 2796:35-72. [PMID: 38856894 DOI: 10.1007/978-1-0716-3818-7_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Fluorescence techniques have been widely used to shed light over the structure-function relationship of potassium channels for the last 40-50 years. In this chapter, we describe how a Förster resonance energy transfer between identical fluorophores (homo-FRET) approach can be applied to study the gating behavior of the prokaryotic channel KcsA. Two different gates have been described to control the K+ flux across the channel's pore, the helix-bundle crossing and the selectivity filter, located at the opposite sides of the channel transmembrane section. Both gates can be studied individually or by using a double-reporter system. Due to its homotetrameric structural arrangement, KcsA presents a high degree of symmetry that fulfills the first requisite to calculate intersubunit distances through this technique. The results obtained through this work have helped to uncover the conformational plasticity of the selectivity filter under different experimental conditions and the importance of its allosteric coupling to the opening of the activation (inner) gate. This biophysical approach usually requires low protein concentration and presents high sensitivity and reproducibility, complementing the high-resolution structural information provided by X-ray crystallography, cryo-EM, and NMR studies.
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Affiliation(s)
- Ana Coutinho
- iBB, Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Associate Laboratory i4HB, Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - José Antonio Poveda
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, Elche, Spain
| | - María Lourdes Renart
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, Elche, Spain.
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3
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Iwamoto M, Morito M, Oiki S, Nishitani Y, Yamamoto D, Matsumori N. Cardiolipin binding enhances KcsA channel gating via both its specific and dianion-monoanion interchangeable sites. iScience 2023; 26:108471. [PMID: 38077151 PMCID: PMC10709135 DOI: 10.1016/j.isci.2023.108471] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Revised: 10/29/2023] [Accepted: 11/13/2023] [Indexed: 01/17/2024] Open
Abstract
KcsA is a potassium channel with a plethora of structural and functional information, but its activity in the KcsA-producing actinomycete membranes remains elusive. To determine lipid species involved in channel-modulation, a surface plasmon resonance (SPR)-based methodology, characterized by immobilization of membrane proteins under a membrane environment, was applied. Dianionic cardiolipin (CL) showed extremely higher affinity for KcsA than monoanionic lipids. The SPR experiments further demonstrated that CL bound not only to the N-terminal M0 helix, a lipid-sensor domain, but to the M0 helix-deleted mutant. In contrast, monoanionic lipids interacted primarily with the M0 helix. This indicates the presence of an alternative CL-binding site, plausibly in the transmembrane domain. Single-channel recordings demonstrated that CL enhanced channel opening in an M0-independent manner. Taken together, the action of monoanionic lipids is exclusively mediated by the M0 helix, while CL binds both the M0 helix and its specific site, further enhancing the channel activity.
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Affiliation(s)
- Masayuki Iwamoto
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Masayuki Morito
- Department of Chemistry, Graduate School of Science, Kyushu University, Fukuoka 819-0395 Japan
| | - Shigetoshi Oiki
- Biomedial Imaging Research Center, University of Fukui, Fukui 910-1193, Japan
| | - Yudai Nishitani
- Department of Applied Physics, Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan
| | - Daisuke Yamamoto
- Department of Applied Physics, Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan
| | - Nobuaki Matsumori
- Department of Chemistry, Graduate School of Science, Kyushu University, Fukuoka 819-0395 Japan
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4
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Renart ML, Giudici AM, Coll-Díez C, González-Ros JM, Poveda JA. Anionic Phospholipids Shift the Conformational Equilibrium of the Selectivity Filter in the KcsA Channel to the Conductive Conformation: Predicted Consequences on Inactivation. Biomedicines 2023; 11:biomedicines11051376. [PMID: 37239046 DOI: 10.3390/biomedicines11051376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/19/2023] [Accepted: 05/03/2023] [Indexed: 05/28/2023] Open
Abstract
Here, we report an allosteric effect of an anionic phospholipid on a model K+ channel, KcsA. The anionic lipid in mixed detergent-lipid micelles specifically induces a change in the conformational equilibrium of the channel selectivity filter (SF) only when the channel inner gate is in the open state. Such change consists of increasing the affinity of the channel for K+, stabilizing a conductive-like form by maintaining a high ion occupancy in the SF. The process is highly specific in several aspects: First, lipid modifies the binding of K+, but not that of Na+, which remains unperturbed, ruling out a merely electrostatic phenomenon of cation attraction. Second, no lipid effects are observed when a zwitterionic lipid, instead of an anionic one, is present in the micelles. Lastly, the effects of the anionic lipid are only observed at pH 4.0, when the inner gate of KcsA is open. Moreover, the effect of the anionic lipid on K+ binding to the open channel closely emulates the K+ binding behaviour of the non-inactivating E71A and R64A mutant proteins. This suggests that the observed increase in K+ affinity caused by the bound anionic lipid should result in protecting the channel against inactivation.
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Affiliation(s)
- María Lourdes Renart
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain
| | - Ana Marcela Giudici
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain
| | - Carlos Coll-Díez
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain
| | - José M González-Ros
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain
| | - José A Poveda
- IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain
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5
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Gao Y, Amon JD, Artzi L, Ramírez-Guadiana FH, Brock KP, Cofsky JC, Marks DS, Kruse AC, Rudner DZ. Bacterial spore germination receptors are nutrient-gated ion channels. Science 2023; 380:387-391. [PMID: 37104613 PMCID: PMC11154005 DOI: 10.1126/science.adg9829] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 03/29/2023] [Indexed: 04/29/2023]
Abstract
Bacterial spores resist antibiotics and sterilization and can remain metabolically inactive for decades, but they can rapidly germinate and resume growth in response to nutrients. Broadly conserved receptors embedded in the spore membrane detect nutrients, but how spores transduce these signals remains unclear. Here, we found that these receptors form oligomeric membrane channels. Mutations predicted to widen the channel initiated germination in the absence of nutrients, whereas those that narrow it prevented ion release and germination in response to nutrients. Expressing receptors with widened channels during vegetative growth caused loss of membrane potential and cell death, whereas the addition of germinants to cells expressing wild-type receptors triggered membrane depolarization. Therefore, germinant receptors act as nutrient-gated ion channels such that ion release initiates exit from dormancy.
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Affiliation(s)
- Yongqiang Gao
- Department of Microbiology, Harvard Medical ScF(2hool, 77 Avenue Louis Pasteur, Boston MA 02115
| | - Jeremy D. Amon
- Department of Microbiology, Harvard Medical ScF(2hool, 77 Avenue Louis Pasteur, Boston MA 02115
- Present Address: Moderna Genomics, 200 Technology Square, Cambridge MA 02139
| | - Lior Artzi
- Department of Microbiology, Harvard Medical ScF(2hool, 77 Avenue Louis Pasteur, Boston MA 02115
- Present Address: Evolved By Nature, 196 Boston Ave, Medford MA 02155
| | | | - Kelly P. Brock
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston MA 02115
- Present Address: Kernal Biologics, 238 Main Street, Cambrdige MA 02142
| | - Joshua C. Cofsky
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston MA 02115
| | - Deborah S. Marks
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston MA 02115
| | - Andrew C. Kruse
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston MA 02115
| | - David Z. Rudner
- Department of Microbiology, Harvard Medical ScF(2hool, 77 Avenue Louis Pasteur, Boston MA 02115
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6
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Gu RX, de Groot BL. Central cavity dehydration as a gating mechanism of potassium channels. Nat Commun 2023; 14:2178. [PMID: 37069187 PMCID: PMC10110622 DOI: 10.1038/s41467-023-37531-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 03/21/2023] [Indexed: 04/19/2023] Open
Abstract
The hydrophobic gating model, in which ion permeation is inhibited by the hydrophobicity, rather than a physical occlusion of the nanopore, functions in various ion channels including potassium channels. Available research focused on the energy barriers for ion/water conduction due to the hydrophobicity, whereas how hydrophobic gating affects the function and structure of channels remains unclear. Here, we use potassium channels as examples and conduct molecular dynamics simulations to investigate this problem. Our simulations find channel activities (ion currents) highly correlated with cavity hydration level, implying insufficient hydration as a barrier for ion permeation. Enforced cavity dehydration successfully induces conformational transitions between known channel states, further implying cavity dewetting as a key step in the gating procedure of potassium channels utilizing different activation mechanisms. Our work reveals how the cavity dewetting is coupled to structural changes of potassium channels and how it affects channel activity. The conclusion may also apply to other ion channels.
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Affiliation(s)
- Ruo-Xu Gu
- School of Life Sciences and Biotechnology, Shanghai Jia Tong University, 800 Dongchuan Road, 200240, Shanghai, China
- Department of Theoretical and Computational Biophysics, Max-Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, 37077, Göttingen, Germany
| | - Bert L de Groot
- Department of Theoretical and Computational Biophysics, Max-Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, 37077, Göttingen, Germany.
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7
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Qing R, Hao S, Smorodina E, Jin D, Zalevsky A, Zhang S. Protein Design: From the Aspect of Water Solubility and Stability. Chem Rev 2022; 122:14085-14179. [PMID: 35921495 PMCID: PMC9523718 DOI: 10.1021/acs.chemrev.1c00757] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Indexed: 12/13/2022]
Abstract
Water solubility and structural stability are key merits for proteins defined by the primary sequence and 3D-conformation. Their manipulation represents important aspects of the protein design field that relies on the accurate placement of amino acids and molecular interactions, guided by underlying physiochemical principles. Emulated designer proteins with well-defined properties both fuel the knowledge-base for more precise computational design models and are used in various biomedical and nanotechnological applications. The continuous developments in protein science, increasing computing power, new algorithms, and characterization techniques provide sophisticated toolkits for solubility design beyond guess work. In this review, we summarize recent advances in the protein design field with respect to water solubility and structural stability. After introducing fundamental design rules, we discuss the transmembrane protein solubilization and de novo transmembrane protein design. Traditional strategies to enhance protein solubility and structural stability are introduced. The designs of stable protein complexes and high-order assemblies are covered. Computational methodologies behind these endeavors, including structure prediction programs, machine learning algorithms, and specialty software dedicated to the evaluation of protein solubility and aggregation, are discussed. The findings and opportunities for Cryo-EM are presented. This review provides an overview of significant progress and prospects in accurate protein design for solubility and stability.
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Affiliation(s)
- Rui Qing
- State
Key Laboratory of Microbial Metabolism, School of Life Sciences and
Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
- Media
Lab, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- The
David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Shilei Hao
- Media
Lab, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- Key
Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400030, China
| | - Eva Smorodina
- Department
of Immunology, University of Oslo and Oslo
University Hospital, Oslo 0424, Norway
| | - David Jin
- Avalon GloboCare
Corp., Freehold, New Jersey 07728, United States
| | - Arthur Zalevsky
- Laboratory
of Bioinformatics Approaches in Combinatorial Chemistry and Biology, Shemyakin−Ovchinnikov Institute of Bioorganic
Chemistry RAS, Moscow 117997, Russia
| | - Shuguang Zhang
- Media
Lab, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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8
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Molecular Events behind the Selectivity and Inactivation Properties of Model NaK-Derived Ion Channels. Int J Mol Sci 2022; 23:ijms23169246. [PMID: 36012519 PMCID: PMC9409022 DOI: 10.3390/ijms23169246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 08/10/2022] [Accepted: 08/14/2022] [Indexed: 11/17/2022] Open
Abstract
Y55W mutants of non-selective NaK and partly K+-selective NaK2K channels have been used to explore the conformational dynamics at the pore region of these channels as they interact with either Na+ or K+. A major conclusion is that these channels exhibit a remarkable pore conformational flexibility. Homo-FRET measurements reveal a large change in W55–W55 intersubunit distances, enabling the selectivity filter (SF) to admit different species, thus, favoring poor or no selectivity. Depending on the cation, these channels exhibit wide-open conformations of the SF in Na+, or tight induced-fit conformations in K+, most favored in the four binding sites containing NaK2K channels. Such conformational flexibility seems to arise from an altered pattern of restricting interactions between the SF and the protein scaffold behind it. Additionally, binding experiments provide clues to explain such poor selectivity. Compared to the K+-selective KcsA channel, these channels lack a high affinity K+ binding component and do not collapse in Na+. Thus, they cannot properly select K+ over competing cations, nor reject Na+ by collapsing, as K+-selective channels do. Finally, these channels do not show C-type inactivation, likely because their submillimolar K+ binding affinities prevent an efficient K+ loss from their SF, thus favoring permanently open channel states.
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9
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High-Resolution Magic Angle Spinning NMR of KcsA in Liposomes: The Highly Mobile C-Terminus. Biomolecules 2022; 12:biom12081122. [PMID: 36009016 PMCID: PMC9405666 DOI: 10.3390/biom12081122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/27/2022] [Accepted: 08/04/2022] [Indexed: 11/25/2022] Open
Abstract
The structure of the transmembrane domain of the pH-activated bacterial potassium channel KcsA has been extensively characterized, yet little information is available on the structure of its cytosolic, functionally critical N- and C-termini. This study presents high-resolution magic angle spinning (HR-MAS) and fractional deuteration as tools to study these poorly resolved regions for proteoliposome-embedded KcsA. Using 1H-detected HR-MAS NMR, we show that the C-terminus transitions from a rigid structure to a more dynamic structure as the solution is rendered acidic. We make previously unreported assignments of residues in the C-terminus of lipid-embedded channels. These data agree with functional models of the C-terminus-stabilizing KcsA tetramers at a neutral pH with decreased stabilization effects at acidic pH. We present evidence that a C-terminal truncation mutation has a destabilizing effect on the KcsA selectivity filter. Finally, we show evidence of hydrolysis of lipids in proteoliposome samples during typical experimental timeframes.
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10
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McGuire H, Blunck R. Studying KcsA Channel Clustering Using Single Channel Voltage-Clamp Fluorescence Imaging*. Front Physiol 2022; 13:863375. [PMID: 35721536 PMCID: PMC9204084 DOI: 10.3389/fphys.2022.863375] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 05/16/2022] [Indexed: 11/13/2022] Open
Abstract
Oligomerization and complex formation play a key role for many membrane proteins and has been described to influence ion channel function in both neurons and the heart. In this study, we observed clustering of single KcsA channels in planar lipid bilayer using single molecule fluorescence, while simultaneously measuring single channel currents. Clustering coincided with cooperative opening of KcsA. We demonstrate that clustering was not caused by direct protein-protein interactions or hydrophobic mismatch with the lipid environment, as suggested earlier, but was mediated via microdomains induced by the channel in the lipid matrix. We found that single channel activity of KcsA requires conically-shaped lipids in the lamellar liquid-crystalline (Lα) phase, and the need for a negative spontaneous curvature seem to lead to the deformations in the membrane that cause the clustering. The method introduced here will be applicable to follow oligomerization of a wide range of membrane proteins.
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Affiliation(s)
- Hugo McGuire
- Department of Physics, Université de Montréal, Montréal, QC, Canada
| | - Rikard Blunck
- Department of Physics, Université de Montréal, Montréal, QC, Canada
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, QC, Canada
- Interdisciplinary Research Center on Brain and Learning (CIRCA), Université de Montréal, Montréal, QC, Canada
- *Correspondence: Rikard Blunck,
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11
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Quaternary structure independent folding of voltage-gated ion channel pore domain subunits. Nat Struct Mol Biol 2022; 29:537-548. [PMID: 35655098 PMCID: PMC9809158 DOI: 10.1038/s41594-022-00775-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Accepted: 04/08/2022] [Indexed: 01/07/2023]
Abstract
Every voltage-gated ion channel (VGIC) has a pore domain (PD) made from four subunits, each comprising an antiparallel transmembrane helix pair bridged by a loop. The extent to which PD subunit structure requires quaternary interactions is unclear. Here, we present crystal structures of a set of bacterial voltage-gated sodium channel (BacNaV) 'pore only' proteins that reveal a surprising collection of non-canonical quaternary arrangements in which the PD tertiary structure is maintained. This context-independent structural robustness, supported by molecular dynamics simulations, indicates that VGIC-PD tertiary structure is independent of quaternary interactions. This fold occurs throughout the VGIC superfamily and in diverse transmembrane and soluble proteins. Strikingly, characterization of PD subunit-binding Fabs indicates that non-canonical quaternary PD conformations can occur in full-length VGICs. Together, our data demonstrate that the VGIC-PD is an autonomously folded unit. This property has implications for VGIC biogenesis, understanding functional states, de novo channel design, and VGIC structural origins.
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12
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Li B, Qin X, Mi LZ. Nanobodies: from structure to applications in non-injectable and bispecific biotherapeutic development. NANOSCALE 2022; 14:7110-7122. [PMID: 35535618 DOI: 10.1039/d2nr00306f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The increasing demand for convenient, miniaturized and multifunctional antibodies necessitates the development of novel antigen-recognition molecules for biological and medical studies. Nanobodies, the functional variable regions of camelid heavy-chain-only antibodies, as a new tool, complement the conventional antibodies and are in the stage of rapid development. The outstanding advantages of nanobodies include a stable structure, easy production, excellent water solubility, high affinity toward antigens and low immunogenicity. With promising application potential, nanobodies are now increasingly applied to various studies, including protein structure analysis, microscopic imaging, medical diagnosis, and drug development. The approval of the first nanobody drug Caplacizumab by the FDA disclosed the therapeutic potential of nanobodies. The outbreak of COVID-19 accelerated the development of nanobody drugs in non-injectable and bispecific biotherapeutic applications. Herein, we reviewed recent studies on the nanobody structure, screening and their applications in protein structure analysis and nanobody drugs, especially on non-injectable nanobody and bispecific nanobody development.
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Affiliation(s)
- Bingxuan Li
- School of Life Sciences, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China.
| | - Xiaohong Qin
- School of Life Sciences, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China.
| | - Li-Zhi Mi
- School of Life Sciences, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China.
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13
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Rohaim A, Slezak T, Koh YH, Blachowicz L, Kossiakoff AA, Roux B. Engineering of a synthetic antibody fragment for structural and functional studies of K+ channels. J Gen Physiol 2022; 154:e202112965. [PMID: 35234830 PMCID: PMC8924934 DOI: 10.1085/jgp.202112965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 01/28/2022] [Indexed: 11/20/2022] Open
Abstract
Engineered antibody fragments (Fabs) have made major impacts on structural biology research, particularly to aid structural determination of membrane proteins. Nonetheless, Fabs generated by traditional monoclonal technology suffer from challenges of routine production and storage. Starting from the known IgG paratopes of an antibody that binds to the "turret loop" of the KcsA K+ channel, we engineered a synthetic Fab (sFab) based upon the highly stable Herceptin Fab scaffold, which can be recombinantly expressed in Escherichia coli and purified with single-step affinity chromatography. This synthetic Fab was used as a crystallization chaperone to obtain crystals of the KcsA channel that diffracted to a resolution comparable to that from the parent Fab. Furthermore, we show that the turret loop can be grafted into the unrelated voltage-gated Kv1.2-Kv2.1 channel and still strongly bind the engineered sFab, in support of the loop grafting strategy. Macroscopic electrophysiology recordings show that the sFab affects the activation and conductance of the chimeric voltage-gated channel. These results suggest that straightforward engineering of antibodies using recombinant formats can facilitate the rapid and scalable production of Fabs as structural biology tools and functional probes. The impact of this approach is expanded significantly based on the potential portability of the turret loop to a myriad of other K+ channels.
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Affiliation(s)
- Ahmed Rohaim
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
- Department of Biophysics, Faculty of Science, Cairo University, Giza, Egypt
| | - Tomasz Slezak
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
| | - Young Hoon Koh
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
| | - Lydia Blachowicz
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
| | - Anthony A. Kossiakoff
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
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14
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Guzman KM, Khosla C. Fragment antigen binding domains (F abs) as tools to study assembly-line polyketide synthases. Synth Syst Biotechnol 2022; 7:506-512. [PMID: 34977395 PMCID: PMC8683866 DOI: 10.1016/j.synbio.2021.12.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/02/2021] [Accepted: 12/03/2021] [Indexed: 12/17/2022] Open
Abstract
The crystallization of proteins remains a bottleneck in our fundamental understanding of their functions. Therefore, discovering tools that aid crystallization is crucial. In this review, the versatility of fragment-antigen binding domains (Fabs) as protein crystallization chaperones is discussed. Fabs have aided the crystallization of membrane-bound and soluble proteins as well as RNA. The ability to bind three Fabs onto a single protein target has demonstrated their potential for crystallization of challenging proteins. We describe a high-throughput workflow for identifying Fabs to aid the crystallization of a protein of interest (POI) by leveraging phage display technologies and differential scanning fluorimetry (DSF). This workflow has proven to be especially effective in our structural studies of assembly-line polyketide synthases (PKSs), which harbor flexible domains and assume transient conformations. PKSs are of interest to us due to their ability to synthesize an unusually broad range of medicinally relevant compounds. Despite years of research studying these megasynthases, their overall topology has remained elusive. One Fab in particular, 1B2, has successfully enabled X-ray crystallographic and single particle cryo-electron microscopic (cryoEM) analyses of multiple modules from distinct assembly-line PKSs. Its use has not only facilitated multidomain protein crystallization but has also enhanced particle quality via cryoEM, thereby enabling the visualization of intact PKS modules at near-atomic (3-5 Å) resolution. The identification of PKS-binding Fabs can be expected to continue playing a key role in furthering our knowledge of polyketide biosynthesis on assembly-line PKSs.
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Affiliation(s)
- Katarina M. Guzman
- Department of Chemical Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Chaitan Khosla
- Department of Chemical Engineering, Stanford University, Stanford, CA, 94305, USA
- Department of Chemistry, Stanford ChEM-H, Stanford University, Stanford, CA, 94305, USA
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15
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Kluge C, Pöhnl M, Böckmann RA. Spontaneous local membrane curvature induced by transmembrane proteins. Biophys J 2022; 121:671-683. [PMID: 35122737 PMCID: PMC8943716 DOI: 10.1016/j.bpj.2022.01.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 01/13/2022] [Accepted: 01/28/2022] [Indexed: 11/26/2022] Open
Abstract
The (local) curvature of cellular membranes acts as a driving force for the targeting of membrane-associated proteins to specific membrane domains, as well as a sorting mechanism for transmembrane proteins, e.g., by accumulation in regions of matching spontaneous curvature. The latter measure was previously experimentally employed to study the curvature induced by the potassium channel KvAP and by aquaporin AQP0. However, the direction of the reported spontaneous curvature levels as well as the molecular driving forces governing the membrane curvature induced by these integral transmembrane proteins could not be addressed experimentally. Here, using both coarse-grained and atomistic molecular dynamics (MD) simulations, we report induced spontaneous curvature values for the homologous potassium channel Kv 1.2/2.1 Chimera (KvChim) and AQP0 embedded in unrestrained lipid bicelles that are in very good agreement with experiment. Importantly, the direction of curvature could be directly assessed from our simulations: KvChim induces a strong positive membrane curvature (≈0.036 nm-1) whereas AQP0 causes a comparably small negative curvature (≈-0.019 nm-1). Analyses of protein-lipid interactions within the bicelle revealed that the potassium channel shapes the surrounding membrane via structural determinants. Differences in shape of the protein-lipid interface of the voltage-gating domains between the extracellular and cytosolic membrane leaflets induce membrane stress and thereby promote a protein-proximal membrane curvature. In contrast, the water pore AQP0 displayed a high structural stability and an only faint effect on the surrounding membrane environment that is connected to its wedge-like shape.
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Affiliation(s)
- Christoph Kluge
- Computational Biology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Matthias Pöhnl
- Computational Biology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Rainer A. Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany,National Center for High-Performance Computing Erlangen (NHR@FAU), Erlangen, Germany,Corresponding author
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16
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Yan T, Liu S, Xu J, Sun H, Yu S, Liu J. Unimolecular Helix-Based Transmembrane Nanochannel with a Smallest Luminal Cavity of 1 Å Expressing High Proton Selectivity and Transport Activity. NANO LETTERS 2021; 21:10462-10468. [PMID: 34860025 DOI: 10.1021/acs.nanolett.1c03858] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Natural protein channels have evolved with exquisite structures to transport ions selectively and rapidly. Learning from nature to construct biomimetic artificial channels is always challenging. Herein we present a unimolecular transmembrane proton channel by quinoline-derived helix, which exhibited highly selective and ultrafast proton transport behaviors. This helix-based channel possesses a small luminal cavity of 1 Å in diameter, which could efficiently reject the permeation of cations, anions or water molecules but only permits the translocation of protons owing to the size effect. The proton flow rate exceeded 107 H+ s-1 channel-1 and reached the same magnitude with gramicidin A. Mechanism investigation revealed that the directionally arrayed NH-chain inside the synthetic channel played a pivotal role during the proton flux. This work not only presented a helix-based channel with the smallest observable nanopore, but also unveiled an unexplored pathway for realizing efficient transport of protons via the consecutive NH-chain.
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Affiliation(s)
- Tengfei Yan
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Shengda Liu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Jiayun Xu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Hongcheng Sun
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Shuangjiang Yu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Junqiu Liu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
- College of Chemistry, State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, China
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17
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Díaz-García C, Renart ML, Poveda JA, Giudici AM, González-Ros JM, Prieto M, Coutinho A. Probing the Structural Dynamics of the Activation Gate of KcsA Using Homo-FRET Measurements. Int J Mol Sci 2021; 22:ijms222111954. [PMID: 34769384 PMCID: PMC8584343 DOI: 10.3390/ijms222111954] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/18/2021] [Accepted: 10/29/2021] [Indexed: 12/16/2022] Open
Abstract
The allosteric coupling between activation and inactivation processes is a common feature observed in K+ channels. Particularly, in the prokaryotic KcsA channel the K+ conduction process is controlled by the inner gate, which is activated by acidic pH, and by the selectivity filter (SF) or outer gate, which can adopt non-conductive or conductive states. In a previous study, a single tryptophan mutant channel (W67 KcsA) enabled us to investigate the SF dynamics using time-resolved homo-Förster Resonance Energy Transfer (homo-FRET) measurements. Here, the conformational changes of both gates were simultaneously monitored after labelling the G116C position with tetramethylrhodamine (TMR) within a W67 KcsA background. At a high degree of protein labeling, fluorescence anisotropy measurements showed that the pH-induced KcsA gating elicited a variation in the homo-FRET efficiency among the conjugated TMR dyes (TMR homo-FRET), while the conformation of the SF was simultaneously tracked (W67 homo-FRET). The dependence of the activation pKa of the inner gate with the ion occupancy of the SF unequivocally confirmed the allosteric communication between the two gates of KcsA. This simple TMR homo-FRET based ratiometric assay can be easily extended to study the conformational dynamics associated with the gating of other ion channels and their modulation.
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Affiliation(s)
- Clara Díaz-García
- iBB, Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (C.D.-G.); (M.P.)
- Associate Laboratory i4HB, Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Maria Lourdes Renart
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain; (J.A.P.); (A.M.G.); (J.M.G.-R.)
- Correspondence: (M.L.R.); (A.C.)
| | - José Antonio Poveda
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain; (J.A.P.); (A.M.G.); (J.M.G.-R.)
| | - Ana Marcela Giudici
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain; (J.A.P.); (A.M.G.); (J.M.G.-R.)
| | - José M. González-Ros
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain; (J.A.P.); (A.M.G.); (J.M.G.-R.)
| | - Manuel Prieto
- iBB, Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (C.D.-G.); (M.P.)
- Associate Laboratory i4HB, Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Ana Coutinho
- iBB, Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (C.D.-G.); (M.P.)
- Associate Laboratory i4HB, Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
- Correspondence: (M.L.R.); (A.C.)
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18
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De Bruyn P, Prolič-Kalinšek M, Vandervelde A, Malfait M, Sterckx YGJ, Sobott F, Hadži S, Pardon E, Steyaert J, Loris R. Nanobody-aided crystallization of the transcription regulator PaaR2 from Escherichia coli O157:H7. Acta Crystallogr F Struct Biol Commun 2021; 77:374-384. [PMID: 34605442 PMCID: PMC8488858 DOI: 10.1107/s2053230x21009006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 08/30/2021] [Indexed: 11/10/2022] Open
Abstract
paaR2-paaA2-parE2 is a three-component toxin-antitoxin module found in prophage CP-993P of Escherichia coli O157:H7. Transcription regulation of this module occurs via the 123-amino-acid regulator PaaR2, which forms a large oligomeric structure. Despite appearing to be well folded, PaaR2 withstands crystallization, as does its N-terminal DNA-binding domain. Native mass spectrometry was used to screen for nanobodies that form a unique complex and stabilize the octameric structure of PaaR2. One such nanobody, Nb33, allowed crystallization of the protein. The resulting crystals belong to space group F432, with unit-cell parameter a = 317 Å, diffract to 4.0 Å resolution and are likely to contain four PaaR2 monomers and four nanobody monomers in the asymmetric unit. Crystals of two truncates containing the N-terminal helix-turn-helix domain also interact with Nb33, and the corresponding co-crystals diffracted to 1.6 and 1.75 Å resolution.
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Affiliation(s)
- Pieter De Bruyn
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Center for Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Maruša Prolič-Kalinšek
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Center for Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Alexandra Vandervelde
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Center for Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Milan Malfait
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Yann G.-J. Sterckx
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Center for Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
- Laboratory of Medical Biochemistry (LMB) and the Infla-Med Centre of Excellence, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
| | - Frank Sobott
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - San Hadži
- Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia
| | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Center for Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Center for Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Remy Loris
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Center for Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
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19
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Folding and misfolding of potassium channel monomers during assembly and tetramerization. Proc Natl Acad Sci U S A 2021; 118:2103674118. [PMID: 34413192 DOI: 10.1073/pnas.2103674118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics and folding of potassium channel pore domain monomers are connected to the kinetics of tetramer assembly. In all-atom molecular dynamics simulations of Kv1.2 and KcsA channels, monomers adopt multiple nonnative conformations while the three helices remain folded. Consistent with this picture, NMR studies also find the monomers to be dynamic and structurally heterogeneous. However, a KcsA construct with a disulfide bridge engineered between the two transmembrane helices has an NMR spectrum with well-dispersed peaks, suggesting that the monomer can be locked into a native-like conformation that is similar to that observed in the folded tetramer. During tetramerization, fluoresence resonance energy transfer (FRET) data indicate that monomers rapidly oligomerize upon insertion into liposomes, likely forming a protein-dense region. Folding within this region occurs along separate fast and slow routes, with τfold ∼40 and 1,500 s, respectively. In contrast, constructs bearing the disulfide bond mainly fold via the faster pathway, suggesting that maintaining the transmembrane helices in their native orientation reduces misfolding. Interestingly, folding is concentration independent despite the tetrameric nature of the channel, indicating that the rate-limiting step is unimolecular and occurs after monomer association in the protein-dense region. We propose that the rapid formation of protein-dense regions may help with the assembly of multimeric membrane proteins by bringing together the nascent components prior to assembly. Finally, despite its name, the addition of KcsA's C-terminal "tetramerization" domain does not hasten the kinetics of tetramerization.
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20
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Gubič Š, Hendrickx LA, Toplak Ž, Sterle M, Peigneur S, Tomašič T, Pardo LA, Tytgat J, Zega A, Mašič LP. Discovery of K V 1.3 ion channel inhibitors: Medicinal chemistry approaches and challenges. Med Res Rev 2021; 41:2423-2473. [PMID: 33932253 PMCID: PMC8252768 DOI: 10.1002/med.21800] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 03/03/2021] [Accepted: 03/19/2021] [Indexed: 12/12/2022]
Abstract
The KV 1.3 voltage-gated potassium ion channel is involved in many physiological processes both at the plasma membrane and in the mitochondria, chiefly in the immune and nervous systems. Therapeutic targeting KV 1.3 with specific peptides and small molecule inhibitors shows great potential for treating cancers and autoimmune diseases, such as multiple sclerosis, type I diabetes mellitus, psoriasis, contact dermatitis, rheumatoid arthritis, and myasthenia gravis. However, no KV 1.3-targeted compounds have been approved for therapeutic use to date. This review focuses on the presentation of approaches for discovering new KV 1.3 peptide and small-molecule inhibitors, and strategies to improve the selectivity of active compounds toward KV 1.3. Selectivity of dalatazide (ShK-186), a synthetic derivate of the sea anemone toxin ShK, was achieved by chemical modification and has successfully reached clinical trials as a potential therapeutic for treating autoimmune diseases. Other peptides and small-molecule inhibitors are critically evaluated for their lead-like characteristics and potential for progression into clinical development. Some small-molecule inhibitors with well-defined structure-activity relationships have been optimized for selective delivery to mitochondria, and these offer therapeutic potential for the treatment of cancers. This overview of KV 1.3 inhibitors and methodologies is designed to provide a good starting point for drug discovery to identify novel effective KV 1.3 modulators against this target in the future.
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Affiliation(s)
- Špela Gubič
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | - Louise A. Hendrickx
- Toxicology and PharmacologyUniversity of Leuven, Campus GasthuisbergLeuvenBelgium
| | - Žan Toplak
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | - Maša Sterle
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | - Steve Peigneur
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | | | - Luis A. Pardo
- AG OncophysiologyMax‐Planck Institute for Experimental MedicineGöttingenGermany
| | - Jan Tytgat
- Toxicology and PharmacologyUniversity of Leuven, Campus GasthuisbergLeuvenBelgium
| | - Anamarija Zega
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
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21
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Kudryashova KS, Nekrasova OV, Kirpichnikov MP, Feofanov AV. Chimeras of KcsA and Kv1 as a bioengineering tool to study voltage-gated potassium channels and their ligands. Biochem Pharmacol 2021; 190:114646. [PMID: 34090876 DOI: 10.1016/j.bcp.2021.114646] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/31/2021] [Accepted: 06/01/2021] [Indexed: 11/28/2022]
Abstract
Chimeric potassium channels KcsA-Kv1, which are among the most intensively studied hybrid membrane proteins to date, were constructed by replacing a part of the pore domain of bacterial potassium channel KcsA (K channel of streptomyces A) with corresponding regions of the mammalian voltage-gated potassium channels belonging to the Kv1 subfamily. In this way, the pore blocker binding site of Kv1 channels was transferred to KcsA, opening up possibility to use the obtained hybrids as receptors of Kv1-channel pore blockers of different origin. In this review the recent progress in KcsA-Kv1 channel design and applications is discussed with a focus on the development of new assays for studying interactions of pore blockers with the channels. A summary of experimental data is presented demonstrating that hybrid channels reproduce the blocker-binding profiles of parental Kv1 channels. It is overviewed how the KcsA-Kv1 chimeras are used to get new insight into the structure of potassium channels, to determine molecular basis for high affinity and selectivity of binding of peptide blockers to Kv1 channels, as well as to identify new peptide ligands.
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Affiliation(s)
- Ksenia S Kudryashova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, 117997 Moscow, Russia
| | - Oksana V Nekrasova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, 117997 Moscow, Russia.
| | - Mikhail P Kirpichnikov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, 117997 Moscow, Russia; Biological Faculty, Lomonosov Moscow State University, Leninskie Gory 1, 119992 Moscow, Russia
| | - Alexey V Feofanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, 117997 Moscow, Russia; Biological Faculty, Lomonosov Moscow State University, Leninskie Gory 1, 119992 Moscow, Russia
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22
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Iwamoto M, Oiki S. Hysteresis of a Tension-Sensitive K + Channel Revealed by Time-Lapse Tension Measurements. JACS AU 2021; 1:467-474. [PMID: 34467309 PMCID: PMC8395652 DOI: 10.1021/jacsau.0c00098] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Indexed: 05/05/2023]
Abstract
Various types of channels vary their function by membrane tension changes upon cellular activities, and lipid bilayer methods allow elucidation of direct interaction between channels and the lipid bilayer. However, the dynamic responsiveness of the channel to the membrane tension remains elusive. Here, we established a time-lapse tension measurement system. A bilayer is formed by docking two monolayer-lined water bubbles, and tension is evaluated via measuring intrabubble pressure as low as <100 Pa (Young-Laplace principle). The prototypical KcsA potassium channel is tension-sensitive, and single-channel current recordings showed that the activation gate exhibited distinct tension sensitivity upon stretching and relaxing. The mechanism underlying the hysteresis is discussed in the mode shift regime, in which the channel protein bears short "memory" in their conformational changes.
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Affiliation(s)
- Masayuki Iwamoto
- Department
of Molecular Neuroscience, University of
Fukui Faculty of Medical Science, 910-1193 Fukui, Japan
| | - Shigetoshi Oiki
- Biomedical
Imaging Research Center, University of Fukui, 910-1193 Fukui, Japan
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23
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Schmidt M, Schroeder I, Bauer D, Thiel G, Hamacher K. Inferring functional units in ion channel pores via relative entropy. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2021; 50:37-57. [PMID: 33523249 PMCID: PMC7872957 DOI: 10.1007/s00249-020-01480-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 10/11/2020] [Accepted: 11/09/2020] [Indexed: 11/25/2022]
Abstract
Coarse-grained protein models approximate the first-principle physical potentials. Among those modeling approaches, the relative entropy framework yields promising and physically sound results, in which a mapping from the target protein structure and dynamics to a model is defined and subsequently adjusted by an entropy minimization of the model parameters. Minimization of the relative entropy is equivalent to maximization of the likelihood of reproduction of (configurational ensemble) observations by the model. In this study, we extend the relative entropy minimization procedure beyond parameter fitting by a second optimization level, which identifies the optimal mapping to a (dimension-reduced) topology. We consider anisotropic network models of a diverse set of ion channels and assess our findings by comparison to experimental results.
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Affiliation(s)
- Michael Schmidt
- Department of Physics, TU Darmstadt, Karolinenpl. 5, 64289 Darmstadt, Germany
| | - Indra Schroeder
- Department of Biology, TU Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany
| | - Daniel Bauer
- Department of Biology, TU Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany
| | - Gerhard Thiel
- Department of Biology, TU Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany
| | - Kay Hamacher
- Department of Physics, Department of Biology, Department of Computer Science, TU Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany
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24
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Giudici AM, Díaz-García C, Renart ML, Coutinho A, Prieto M, González-Ros JM, Poveda JA. Tetraoctylammonium, a Long Chain Quaternary Ammonium Blocker, Promotes a Noncollapsed, Resting-Like Inactivated State in KcsA. Int J Mol Sci 2021; 22:ijms22020490. [PMID: 33419017 PMCID: PMC7825302 DOI: 10.3390/ijms22020490] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 12/28/2020] [Accepted: 01/01/2021] [Indexed: 02/06/2023] Open
Abstract
Alkylammonium salts have been used extensively to study the structure and function of potassium channels. Here, we use the hydrophobic tetraoctylammonium (TOA+) to shed light on the structure of the inactivated state of KcsA, a tetrameric prokaryotic potassium channel that serves as a model to its homologous eukaryotic counterparts. By the combined use of a thermal denaturation assay and the analysis of homo-Förster resonance energy transfer in a mutant channel containing a single tryptophan (W67) per subunit, we found that TOA+ binds the channel cavity with high affinity, either with the inner gate open or closed. Moreover, TOA+ bound at the cavity allosterically shifts the equilibrium of the channel's selectivity filter conformation from conductive to an inactivated-like form. The inactivated TOA+-KcsA complex exhibits a loss in the affinity towards permeant K+ at pH 7.0, when the channel is in its closed state, but maintains the two sets of K+ binding sites and the W67-W67 intersubunit distances characteristic of the selectivity filter in the channel resting state. Thus, the TOA+-bound state differs clearly from the collapsed channel state described by X-ray crystallography and claimed to represent the inactivated form of KcsA.
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Affiliation(s)
- Ana Marcela Giudici
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, E-03202 Elche, Spain; (A.M.G.); (M.L.R.)
| | - Clara Díaz-García
- Institute for Bioengineering and Bioscience (IBB), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (C.D.-G.); (A.C.); (M.P.)
| | - Maria Lourdes Renart
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, E-03202 Elche, Spain; (A.M.G.); (M.L.R.)
| | - Ana Coutinho
- Institute for Bioengineering and Bioscience (IBB), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (C.D.-G.); (A.C.); (M.P.)
- Departamento de Química e Bioquímica, Faculty of Sciences, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Manuel Prieto
- Institute for Bioengineering and Bioscience (IBB), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (C.D.-G.); (A.C.); (M.P.)
| | - José M. González-Ros
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, E-03202 Elche, Spain; (A.M.G.); (M.L.R.)
- Correspondence: (J.M.G.-R.); (J.A.P.); Tel.: +34-966-658-757 (J.M.G.-R.); +34-966-658-466 (J.A.P.)
| | - José Antonio Poveda
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, E-03202 Elche, Spain; (A.M.G.); (M.L.R.)
- Correspondence: (J.M.G.-R.); (J.A.P.); Tel.: +34-966-658-757 (J.M.G.-R.); +34-966-658-466 (J.A.P.)
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25
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Miao Y, Lam D, Zhuang J, Zhu J, Poget SF, Tang M. Membrane Topology of an Ion Channel Detected by Solid-State Nuclear Magnetic Resonance and Paramagnetic Effects. J Phys Chem Lett 2020; 11:9795-9801. [PMID: 33151058 DOI: 10.1021/acs.jpclett.0c02014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Ion channels are often targeted by toxins or other ligands to modify their channel activities and alter ion conductance. Interactions between toxins and ion channels could result in changes in membrane insertion depth for residues close to the binding site. Paramagnetic solid-state nuclear magnetic resonance (SSNMR) has shown great potential in providing structural information on membrane samples. We used KcsA as a model ion channel to investigate how the paramagnetic effects of Mn2+ and Dy3+ ions with headgroup-modified chelator lipids would influence the SSNMR signals of membrane proteins in proteoliposomes. Spectral comparisons have shown significant changes of peak intensities for the residues in the loop or terminal regions due to paramagnetic effects corresponding to the close proximity to the membrane surface. Hence, these results demonstrate that paramagnetic SSNMR can be used to detect surface residues based on the topology and membrane insertion properties for integral membrane proteins.
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Affiliation(s)
- Yimin Miao
- Department of Chemistry, College of Staten Island-Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
| | - Dennis Lam
- Department of Chemistry, College of Staten Island-Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
| | - Jianqin Zhuang
- Department of Chemistry, College of Staten Island-Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
| | - Jing Zhu
- Department of Chemistry, College of Staten Island-Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
| | - Sebastien F Poget
- Department of Chemistry, College of Staten Island-Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
| | - Ming Tang
- Department of Chemistry, College of Staten Island-Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, New York 10016, United States
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26
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Iwahashi Y, Toyama Y, Imai S, Itoh H, Osawa M, Inoue M, Shimada I. Conformational equilibrium shift underlies altered K + channel gating as revealed by NMR. Nat Commun 2020; 11:5168. [PMID: 33057011 PMCID: PMC7560842 DOI: 10.1038/s41467-020-19005-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 09/23/2020] [Indexed: 01/30/2023] Open
Abstract
The potassium ion (K+) channel plays a fundamental role in controlling K+ permeation across the cell membrane and regulating cellular excitabilities. Mutations in the transmembrane pore reportedly affect the gating transitions of K+ channels, and are associated with the onset of neural disorders. However, due to the lack of structural and dynamic insights into the functions of K+ channels, the structural mechanism by which these mutations cause K+ channel dysfunctions remains elusive. Here, we used nuclear magnetic resonance spectroscopy to investigate the structural mechanism underlying the decreased K+-permeation caused by disease-related mutations, using the prokaryotic K+ channel KcsA. We demonstrated that the conformational equilibrium in the transmembrane region is shifted toward the non-conductive state with the closed intracellular K+-gate in the disease-related mutant. We also demonstrated that this equilibrium shift is attributable to the additional steric contacts in the open-conductive structure, which are evoked by the increased side-chain bulkiness of the residues lining the transmembrane helix. Our results suggest that the alteration in the conformational equilibrium of the intracellular K+-gate is one of the fundamental mechanisms underlying the dysfunctions of K+ channels caused by disease-related mutations. Potassium ion channels control K+ permeation across cell membranes and mutations that cause cardiovascular and neural diseases are known. Here, the authors perform NMR measurements with the prototypical K+ channel from Streptomyces lividans, KcsA and characterise the effects of disease causing mutations on the conformational dynamics of K+ channels in a physiological solution environment.
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Affiliation(s)
- Yuta Iwahashi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yuki Toyama
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Shunsuke Imai
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hiroaki Itoh
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masanori Osawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.,Keio University Faculty of Pharmacy, Shibakoen, Minato-ku, Tokyo, 105-8512, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Ichio Shimada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. .,RIKEN Center for Biosystems Dynamics Research, Kanagawa, 230-0045, Japan.
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27
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Callahan KM, Mondou B, Sasseville L, Schwartz JL, D'Avanzo N. The influence of membrane bilayer thickness on KcsA channel activity. Channels (Austin) 2020; 13:424-439. [PMID: 31608774 PMCID: PMC6802934 DOI: 10.1080/19336950.2019.1676367] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
Atomic resolution structures have provided significant insight into the gating and permeation mechanisms of various ion channels, including potassium channels. However, ion channels may also be regulated by numerous factors, including the physiochemical properties of the membrane in which they are embedded. For example, the matching of the bilayer's hydrophobic region to the hydrophobic external surface of the ion channel is thought to minimize the energetic penalty needed to solvate hydrophobic residues or exposed lipid tails. To understand the molecular basis of such regulation by hydrophobic matching requires examining channels in the presence of the lipid membrane. Here we examine the role of hydrophobic matching in regulating the activity of the model potassium channel, KcsA. 86Rb+ influx assays and single-channel recordings indicate that the non-inactivating E71A KcsA channel is most active in thin bilayers (<diC18:1PC). Bilayer thickness affects the open probability of KcsA and not its unitary conductance. Molecular dynamics simulations indicate that the bilayer can sufficiently modify its dimensions to accommodate KcsA channels without major perturbations in the protein helical packing within the nanosecond timescale. Based on experimental results and MD simulations, we present a model in which bilayer thickness influences the stability of the open and closed conformations of the intracellular gate of KcsA, with minimal impact on the stability of the selectivity filter of the non-inactivating mutant, E71A.
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Affiliation(s)
- Karen M Callahan
- From the Département de pharmacologie et physiologie, Faculté de médecine, Université de Montréal , Montréal , Canada
| | - Benoit Mondou
- Département de biochimie et médecine moléculaire, Université de Montréal , Montréal , Canada
| | - Louis Sasseville
- From the Département de pharmacologie et physiologie, Faculté de médecine, Université de Montréal , Montréal , Canada
| | - Jean-Louis Schwartz
- From the Département de pharmacologie et physiologie, Faculté de médecine, Université de Montréal , Montréal , Canada.,Département de biochimie et médecine moléculaire, Université de Montréal , Montréal , Canada.,Centre SÈVE, Université de Sherbrooke , Sherbrooke , Canada
| | - Nazzareno D'Avanzo
- From the Département de pharmacologie et physiologie, Faculté de médecine, Université de Montréal , Montréal , Canada.,Département de biochimie et médecine moléculaire, Université de Montréal , Montréal , Canada
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28
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Generating therapeutic monoclonal antibodies to complex multi-spanning membrane targets: Overcoming the antigen challenge and enabling discovery strategies. Methods 2020; 180:111-126. [PMID: 32422249 DOI: 10.1016/j.ymeth.2020.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/21/2020] [Accepted: 05/13/2020] [Indexed: 12/17/2022] Open
Abstract
Complex integral membrane proteins, which are embedded in the cell surface lipid bilayer by multiple transmembrane spanning helices, encompass families of proteins which are important target classes for drug discovery. These protein families include G protein-coupled receptors, ion channels and transporters. Although these proteins have typically been targeted by small molecule drugs and peptides, the high specificity of monoclonal antibodies offers a significant opportunity to selectively modulate these target proteins. However, it remains the case that isolation of antibodies with desired pharmacological function(s) has proven difficult due to technical challenges in preparing membrane protein antigens suitable to support antibody drug discovery. In this review recent progress in defining strategies for generation of membrane protein antigens is outlined. We also highlight antibody isolation strategies which have generated antibodies which bind the membrane protein and modulate the protein function.
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29
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Probing allosteric coupling in a constitutively open mutant of the ion channel KcsA using solid-state NMR. Proc Natl Acad Sci U S A 2020; 117:7171-7175. [PMID: 32188782 DOI: 10.1073/pnas.1908828117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Transmembrane allosteric coupling is a feature of many critical biological signaling events. Here we test whether transmembrane allosteric coupling controls the potassium binding affinity of the prototypical potassium channel KcsA in the context of C-type inactivation. Activation of KcsA is initiated by proton binding to the pH gate upon an intracellular drop in pH. Numerous studies have suggested that this proton binding also prompts a conformational switch, leading to a loss of affinity for potassium ions at the selectivity filter and therefore to channel inactivation. We tested this mechanism for inactivation using a KcsA mutant (H25R/E118A) that exhibits an open pH gate across a broad range of pH values. We present solid-state NMR measurements of this open mutant at neutral pH to probe the affinity for potassium at the selectivity filter. The potassium binding affinity in the selectivity filter of this mutant, 81 mM, is about four orders of magnitude weaker than that of wild-type KcsA at neutral pH and is comparable to the value for wild-type KcsA at low pH (pH ≈ 3.5). This result strongly supports our assertion that the open pH gate allosterically affects the potassium binding affinity of the selectivity filter. In this mutant, the protonation state of a glutamate residue (E120) in the pH sensor is sensitive to potassium binding, suggesting that this mutant also has flexibility in the activation gate and is subject to transmembrane allostery.
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30
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Mitropoulou AN, Ceska T, Heads JT, Beavil AJ, Henry AJ, McDonnell JM, Sutton BJ, Davies AM. Engineering the Fab fragment of the anti-IgE omalizumab to prevent Fab crystallization and permit IgE-Fc complex crystallization. Acta Crystallogr F Struct Biol Commun 2020; 76:116-129. [PMID: 32133997 PMCID: PMC7057348 DOI: 10.1107/s2053230x20001466] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 02/03/2020] [Indexed: 12/01/2022] Open
Abstract
Immunoglobulin E (IgE) plays a central role in the allergic response, in which cross-linking of allergen by FcεRI-bound IgE triggers mast cell and basophil degranulation and the release of inflammatory mediators. The high-affinity interaction between IgE and FcεRI is a long-standing target for therapeutic intervention in allergic disease. Omalizumab is a clinically approved anti-IgE monoclonal antibody that binds to free IgE, also with high affinity, preventing its interaction with FcεRI. All attempts to crystallize the pre-formed complex between the omalizumab Fab and the Fc region of IgE (IgE-Fc), to understand the structural basis for its mechanism of action, surprisingly failed. Instead, the Fab alone selectively crystallized in different crystal forms, but their structures revealed intermolecular Fab/Fab interactions that were clearly strong enough to disrupt the Fab/IgE-Fc complexes. Some of these interactions were common to other Fab crystal structures. Mutations were therefore designed to disrupt two recurring packing interactions observed in the omalizumab Fab crystal structures without interfering with the ability of the omalizumab Fab to recognize IgE-Fc; this led to the successful crystallization and subsequent structure determination of the Fab/IgE-Fc complex. The mutagenesis strategy adopted to achieve this result is applicable to other intractable Fab/antigen complexes or systems in which Fabs are used as crystallization chaperones.
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Affiliation(s)
- Alkistis N. Mitropoulou
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Tom Ceska
- UCB Celltech, 208 Bath Road, Slough SL1 3WE, UK
| | | | - Andrew J. Beavil
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | | | - James M. McDonnell
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Brian J. Sutton
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Anna M. Davies
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
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31
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Maiuri M, Garavelli M, Cerullo G. Ultrafast Spectroscopy: State of the Art and Open Challenges. J Am Chem Soc 2019; 142:3-15. [DOI: 10.1021/jacs.9b10533] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Margherita Maiuri
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Marco Garavelli
- Dipartimento di Chimica Industriale, Università degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Giulio Cerullo
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
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32
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Chill JH, Qasim A, Sher I, Gross R. NMR Perspectives of the KcsA Potassium Channel in the Membrane Environment. Isr J Chem 2019. [DOI: 10.1002/ijch.201900107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jordan H. Chill
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
| | - Arwa Qasim
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
| | - Inbal Sher
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
| | - Renana Gross
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
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33
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Xu Y, McDermott AE. Inactivation in the potassium channel KcsA. JOURNAL OF STRUCTURAL BIOLOGY-X 2019; 3:100009. [PMID: 32647814 PMCID: PMC7337057 DOI: 10.1016/j.yjsbx.2019.100009] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 05/17/2019] [Accepted: 06/04/2019] [Indexed: 12/17/2022]
Abstract
C-type inactivation in potassium channels is a nearly universal regulatory mechanism. A major hypothesis states that C-type inactivation involves ion loss at the selectivity filter as an allosteric response to activation. NMR is used to probe protein conformational changes in response to pH and [K+], demonstrating that H+ and K+ binding are allosterically coupled in KcsA. The lipids are integrated parts of potassium channels in terms of structure, energetics and function.
Inactivation, the slow cessation of transmission after activation, is a general feature of potassium channels. It is essential for their function, and malfunctions in inactivation leads to numerous pathologies. The detailed mechanism for the C-type inactivation, distinct from the N-type inactivation, remains an active area of investigation. Crystallography, computational simulations, and NMR have greatly enriched our understanding of the process. Here we review the major hypotheses regarding C-type inactivation, particularly focusing on the key role played by NMR studies of the prokaryotic potassium channel KcsA, which serves as a good model for voltage gated mammalian channels.
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Affiliation(s)
- Yunyao Xu
- Department of Chemistry, Columbia University, New York, NY 10027, United States
| | - Ann E McDermott
- Department of Chemistry, Columbia University, New York, NY 10027, United States
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34
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Diffracted X-ray tracking method for recording single-molecule protein motions. Biochim Biophys Acta Gen Subj 2019; 1864:129361. [PMID: 31077793 DOI: 10.1016/j.bbagen.2019.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 04/25/2019] [Accepted: 05/05/2019] [Indexed: 11/24/2022]
Abstract
BACKGROUND Proteins change their conformation depending on function. Although a vast number of static pictures of proteins have been accumulated, information regarding their dynamics in function is limited. Diffracted X-ray tracking (DXT) is a good candidate to obtain the missing data. SCOPE OF REVIEW A gold nanocrystal was attached to the target protein as a probe and the motion of the X-ray diffraction spots from the crystal corresponded to the motion of the target. Although it has advantages of high temporal (sub-millisecond) and spatial (approximately 0.1°) resolutions, it is not extensively utilized. This review focused on its effective application from a user's perspective. We also present an example with the KcsA channel and the status of recent developments to show the future possibilities of the method. MAJOR CONCLUSIONS DXT is a powerful method to investigate intramolecular structural changes. For instance, in the KcsA channel, the method revealed a wave of conformational changes transmitted from the gate region to the end of the molecule. The method is continuously being developed, and users can choose an appropriate measurement system depending on the condition of their sample. GENERAL SIGNIFICANCE Revealing the protein structural changes with respect to function is an important frontier. The most distinctive feature of the DXT method is that both high temporal and spatial resolutions are achievable, and it is possible to track the motions of multiple molecules at the same time. This feature is an advantage for screening molecules associated with the target proteins (e.g., ligands and medicines).
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35
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Conformational plasticity in the KcsA potassium channel pore helix revealed by homo-FRET studies. Sci Rep 2019; 9:6215. [PMID: 30996281 PMCID: PMC6470172 DOI: 10.1038/s41598-019-42405-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 03/29/2019] [Indexed: 11/24/2022] Open
Abstract
Potassium channels selectivity filter (SF) conformation is modulated by several factors, including ion-protein and protein-protein interactions. Here, we investigate the SF dynamics of a single Trp mutant of the potassium channel KcsA (W67) using polarized time-resolved fluorescence measurements. For the first time, an analytical framework is reported to analyze the homo-Förster resonance energy transfer (homo-FRET) within a symmetric tetrameric protein with a square geometry. We found that in the closed state (pH 7), the W67-W67 intersubunit distances become shorter as the average ion occupancy of the SF increases according to cation type and concentration. The hypothesis that the inactivated SF at pH 4 is structurally similar to its collapsed state, detected at low K+, pH 7, was ruled out, emphasizing the critical role played by the S2 binding site in the inactivation process of KcsA. This homo-FRET approach provides complementary information to X-ray crystallography in which the protein conformational dynamics is usually compromised.
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36
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Eichmann C, Frey L, Maslennikov I, Riek R. Probing Ion Binding in the Selectivity Filter of the KcsA Potassium Channel. J Am Chem Soc 2019; 141:7391-7398. [DOI: 10.1021/jacs.9b01092] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Cédric Eichmann
- Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Lukas Frey
- Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland
| | | | - Roland Riek
- Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland
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37
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Qasim A, Sher I, Hirschhorn O, Shaked H, Qasem Z, Ruthstein S, Chill JH. Investigation of a KcsA Cytoplasmic pH Gate in Lipoprotein Nanodiscs. Chembiochem 2019; 20:813-821. [PMID: 30565824 DOI: 10.1002/cbic.201800627] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Indexed: 12/14/2022]
Abstract
The bacterial potassium channel KcsA is gated by pH, opening for conduction under acidic conditions. Molecular determinants responsible for this effect have been identified at the extracellular selectivity filter, at the membrane-cytoplasm interface (TM2 gate), and in the cytoplasmic C-terminal domain (CTD), an amphiphilic four-helix bundle mediated by hydrophobic and electrostatic interactions. Here we have employed NMR and EPR to provide a structural view of the pH-induced open-to-closed CTD transition. KcsA was embedded in lipoprotein nanodiscs (LPNs), selectively methyl-protonated at Leu/Val residues to allow observation of both states by NMR, and spin-labeled for the purposes of EPR studies. We observed a pHinduced structural change between an associated structured CTD at neutral pH and a dissociated flexible CTD at acidic pH, with a transition in the 5.0-5.5 range, consistent with a stabilization of the CTD by channel architecture. A double mutant constitutively open at the TM2 gate exhibited reduced stability of associated CTD, as indicated by weaker spin-spin interactions, a shift to higher transition pH values, and a tenfold reduction in the population of the associated "closed" channels. We extended these findings for isolated CTD-derived peptides to full-length KcsA and have established a contribution of the CTD to KcsA pH-controlled gating, which exhibits a strong correlation with the state of the proximal TM2 gate.
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Affiliation(s)
- Arwa Qasim
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Inbal Sher
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Orel Hirschhorn
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Hadassa Shaked
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Zena Qasem
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Sharon Ruthstein
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
| | - Jordan H Chill
- Department of Chemistry, Bar Ilan University, Ramat Gan, 52900, Israel
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38
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Gupta S. Using X-ray Footprinting and Mass Spectrometry to Study the Structure and Function of Membrane Proteins. Protein Pept Lett 2019; 26:44-54. [PMID: 30484402 DOI: 10.2174/0929866526666181128142401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 10/22/2018] [Accepted: 11/06/2018] [Indexed: 11/22/2022]
Abstract
BACKGROUND Membrane proteins are crucial for cellular sensory cascades and metabolite transport, and hence are key pharmacological targets. Structural studies by traditional highresolution techniques are limited by the requirements for high purity and stability when handled in high concentration and nonnative buffers. Hence, there is a growing requirement for the use of alternate methods in a complementary but orthogonal approach to study the dynamic and functional aspects of membrane proteins in physiologically relevant conditions. In recent years, significant progress has been made in the field of X-ray radiolytic labeling in combination with mass spectroscopy, commonly known as X-ray Footprinting and Mass Spectrometry (XFMS), which provide residue-specific information on the solvent accessibility of proteins. In combination with both lowresolution biophysical methods and high-resolution structural data, XFMS is capable of providing valuable insights into structure and dynamics of membrane proteins, which have been difficult to obtain by standalone high-resolution structural techniques. The XFMS method has also demonstrated a unique capability for identification of structural waters and their dynamics in protein cavities at both a high degree of spatial and temporal resolution, and thus capable of identifying conformational hot-spots in transmembrane proteins. CONCLUSION We provide a perspective on the place of XFMS amongst other structural biology methods and showcase some of the latest developments in its usage for studying conformational changes in membrane proteins.
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Affiliation(s)
- Sayan Gupta
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
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39
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Vasseur L, Chavanieu A, Combemale S, Caumes C, Béroud R, De Waard M, Ducrot P, Boutin JA, Ferry G, Cens T. Fluorescent analogues of BeKm-1 with high and specific activity against the hERG channel. Toxicon X 2019; 2:100010. [PMID: 32550567 PMCID: PMC7285999 DOI: 10.1016/j.toxcx.2019.100010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 01/30/2019] [Accepted: 02/13/2019] [Indexed: 12/30/2022] Open
Abstract
Peptidic toxins that target specifically mammalian channels and receptors can be found in the venom of animals. These toxins are rarely used directly as tools for biochemical experiments, and need to be modified via the attachment of chemical groups (e.g., radioactive or fluorescent moieties). Ideally, such modifications should maintain the toxin specificity and affinity for its target. With the goal of obtaining fluorescent derivatives of BeKm-1, a toxin from the scorpion species Buthus eupeus that selectively inhibits the voltage-gated potassium ion channel hERG, we produced four active analogues using a model of BeKm-1 docking to the outer mouth of the channel. In these BeKm-1 analogues, the natural peptide was linked to the fluorescent cyanine 5 (Cy5) probe via four different linkers at Arg1 or Arg/Lys27. All analogues retained their specificity towards the hERG channel in electrophysiological experiments but displayed a lesser affinity. These results validate our strategy for designing toxin analogues and demonstrate that different chemical groups can be attached to different residues of BeKm-1. Recent structural data on the hERG ion channel allow modeling BeKm-1 docking to the outer mouth of the channel. The docking model identified solvent-exposed residues in BeKm-1 sequence for the attachment of chemical groups. Four BeKm-1 analogues were produced by labeling with a fluorescent dye the end of four different linkers. Electrophysiological recordings demonstrated that BeKm-1 analogues retain the toxin affinity and specificity towards hERG.
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Affiliation(s)
- Lucie Vasseur
- Institut des Biomolécules Max Mousseron, Université de Montpellier, Montpellier, France
| | - Alain Chavanieu
- Institut des Biomolécules Max Mousseron, Université de Montpellier, Montpellier, France
| | | | | | | | - Michel De Waard
- Smartox Biotechnology, Saint-Egrève, France.,Institut du Thorax, Inserm UMR 1087/CNRS UMR 6291, LabEx « Ion Channels, Science & Therapeutics », Nantes, France
| | - Pierre Ducrot
- Pole d'expertise Biotechnologie, Chimie, Biologie, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Jean A Boutin
- Pole d'expertise Biotechnologie, Chimie, Biologie, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Gilles Ferry
- Pole d'expertise Biotechnologie, Chimie, Biologie, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Thierry Cens
- Institut des Biomolécules Max Mousseron, Université de Montpellier, Montpellier, France
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40
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Schönrock M, Thiel G, Laube B. Coupling of a viral K +-channel with a glutamate-binding-domain highlights the modular design of ionotropic glutamate-receptors. Commun Biol 2019; 2:75. [PMID: 30820470 PMCID: PMC6385376 DOI: 10.1038/s42003-019-0320-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 01/22/2019] [Indexed: 01/12/2023] Open
Abstract
Ionotropic glutamate receptors (iGluRs) mediate excitatory neuronal signaling in the mammalian CNS. These receptors are critically involved in diverse physiological processes; including learning and memory formation, as well as neuronal damage associated with neurological diseases. Based on partial sequence and structural similarities, these complex cation-permeable iGluRs are thought to descend from simple bacterial proteins emerging from a fusion of a substrate binding protein (SBP) and an inverted potassium (K+)-channel. Here, we fuse the pore module of the viral K+-channel KcvATCV-1 to the isolated glutamate-binding domain of the mammalian iGluR subunit GluA1 which is structural homolog to SBPs. The resulting chimera (GluATCV*) is functional and displays the ligand recognition characteristics of GluA1 and the K+-selectivity of KcvATCV-1. These results are consistent with a conserved activation mechanism between a glutamate-binding domain and the pore-module of a K+-channel and support the expected phylogenetic link between the two protein families.
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Affiliation(s)
- Michael Schönrock
- Department of Biology, Neurophysiology and Neurosensory Systems, Technische Universität Darmstadt, 64289, Darmstadt, Germany
| | - Gerhard Thiel
- Department of Biology, Plant Membrane Biophysics, Technische Universität Darmstadt, 64289, Darmstadt, Germany
| | - Bodo Laube
- Department of Biology, Neurophysiology and Neurosensory Systems, Technische Universität Darmstadt, 64289, Darmstadt, Germany.
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41
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Giudici AM, Renart ML, Díaz-García C, Morales A, Poveda JA, González-Ros JM. Accessibility of Cations to the Selectivity Filter of KcsA in the Inactivated State: An Equilibrium Binding Study. Int J Mol Sci 2019; 20:ijms20030689. [PMID: 30764559 PMCID: PMC6387330 DOI: 10.3390/ijms20030689] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 01/25/2019] [Accepted: 01/25/2019] [Indexed: 12/29/2022] Open
Abstract
Cation binding under equilibrium conditions has been used as a tool to explore the accessibility of permeant and nonpermeant cations to the selectivity filter in three different inactivated models of the potassium channel KcsA. The results show that the stack of ion binding sites (S1 to S4) in the inactivated filter models remain accessible to cations as they are in the resting channel state. The inactivated state of the selectivity filter is therefore “resting-like” under such equilibrium conditions. Nonetheless, quantitative differences in the apparent KD’s of the binding processes reveal that the affinity for the binding of permeant cations to the inactivated channel models, mainly K+, decreases considerably with respect to the resting channel. This is likely to cause a loss of K+ from the inactivated filter and consequently, to promote nonconductive conformations. The most affected site by the affinity loss seems to be S4, which is interesting because S4 is the first site to accommodate K+ coming from the channel vestibule when K+ exits the cell. Moreover, binding of the nonpermeant species, Na+, is not substantially affected by inactivation, meaning that the inactivated channels are also less selective for permeant versus nonpermeant cations under equilibrium conditions.
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Affiliation(s)
- Ana Marcela Giudici
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), and Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, Elche, E-03202 Alicante, Spain.
| | - Maria Lourdes Renart
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), and Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, Elche, E-03202 Alicante, Spain.
| | - Clara Díaz-García
- CQFM-IN and IBB-Institute for Bioengineering and Bioscience, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal.
| | - Andrés Morales
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, E-03080 Alicante, Spain.
| | - José Antonio Poveda
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), and Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, Elche, E-03202 Alicante, Spain.
| | - José Manuel González-Ros
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), and Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, Elche, E-03202 Alicante, Spain.
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42
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Abstract
Ion channels are essential for cellular signaling. Voltage-gated ion channels (VGICs) are the largest and most extensively studied superfamily of ion channels. They possess modular structural features such as voltage-sensing domains that encircle and form mechanical connections with the pore-forming domains. Such features are intimately related to their function in sensing and responding to changes in the membrane potential. In the present work, we discuss the thermodynamic mechanisms of the VGIC superfamily, including the two-state gating mechanism, sliding-rocking mechanism of the voltage sensor, subunit cooperation, lipid-infiltration mechanism of inactivation, and the relationship with their structural features.
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43
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Anomalous X-ray diffraction studies of ion transport in K + channels. Nat Commun 2018; 9:4540. [PMID: 30382100 PMCID: PMC6208422 DOI: 10.1038/s41467-018-06957-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 09/24/2018] [Indexed: 11/16/2022] Open
Abstract
Potassium ion channels utilize a highly selective filter to rapidly transport K+ ions across cellular membranes. This selectivity filter is composed of four binding sites which display almost equal electron density in crystal structures with high potassium ion concentrations. This electron density can be interpreted to reflect a superposition of alternating potassium ion and water occupied states or as adjacent potassium ions. Here, we use single wavelength anomalous dispersion (SAD) X-ray diffraction data collected near the potassium absorption edge to show experimentally that all ion binding sites within the selectivity filter are fully occupied by K+ ions. These data support the hypothesis that potassium ion transport occurs by direct Coulomb knock-on, and provide an example of solving the phase problem by K-SAD. The number of K+ occupied binding sites in the selectivity filter of potassium ion channels is still under debate. Here, the authors collect diffraction data on the K+ selective NaK channel NaK2K at a wavelength of 3.35 Å, close to the K absorption edge, revealing that all four binding sites in the selectivity filter are fully occupied by K+ ions.
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44
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Li X, Sevillano N, La Greca F, Hsu J, Mathews II, Matsui T, Craik CS, Khosla C. Discovery and Characterization of a Thioesterase-Specific Monoclonal Antibody That Recognizes the 6-Deoxyerythronolide B Synthase. Biochemistry 2018; 57:6201-6208. [PMID: 30289692 DOI: 10.1021/acs.biochem.8b00886] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Assembly line polyketide synthases (PKSs) are large multimodular enzymes responsible for the biosynthesis of diverse antibiotics in bacteria. Structural and mechanistic analysis of these megasynthases can benefit from the discovery of reagents that recognize individual domains or linkers in a site-specific manner. Monoclonal antibodies not only have proven themselves as premier tools in analogous applications but also have the added benefit of constraining the conformational flexibility of their targets in unpredictable but often useful ways. Here we have exploited a library based on the naïve human antibody repertoire to discover a Fab (3A6) that recognizes the terminal thioesterase (TE) domain of the 6-deoxyerythronolide B synthase with high specificity. Biochemical assays were used to verify that 3A6 binding does not inhibit enzyme turnover. The co-crystal structure of the TE-3A6 complex was determined at 2.45 Å resolution, resulting in atomic characterization of this protein-protein recognition mechanism. Fab binding had minimal effects on the structural integrity of the TE. In turn, these insights were used to interrogate via small-angle X-ray scattering the solution-phase conformation of 3A6 complexed to a catalytically competent PKS module and bimodule. Altogether, we have developed a high-affinity monoclonal antibody tool that recognizes the TE domain of the 6-deoxyerythronolide B synthase while maintaining its native function.
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Affiliation(s)
| | - Natalia Sevillano
- Department of Pharmaceutical Chemistry , University of California San Francisco , San Francisco , California 94158 , United States
| | - Florencia La Greca
- Department of Pharmaceutical Chemistry , University of California San Francisco , San Francisco , California 94158 , United States
| | | | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Tsutomu Matsui
- Department of Pharmaceutical Chemistry , University of California San Francisco , San Francisco , California 94158 , United States
| | - Charles S Craik
- Department of Pharmaceutical Chemistry , University of California San Francisco , San Francisco , California 94158 , United States
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45
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Hirano M, Ide T. Electrostatic state of the cytoplasmic domain influences inactivation at the selectivity filter of the KcsA potassium channel. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:220-227. [PMID: 30053405 DOI: 10.1016/j.bbamem.2018.07.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 07/20/2018] [Accepted: 07/23/2018] [Indexed: 12/23/2022]
Abstract
KcsA is a proton-activated K+ channel that is regulated at two gates: an activation gate located in the inner entrance of the pore and an inactivation gate at the selectivity filter. Previously, we revealed that the cytoplasmic domain (CPD) of KcsA senses proton and that electrostatic changes of the CPD influences the opening and closing of the activation gate. However, our previous studies did not reveal the effect of CPD on the inactivation gate because we used a non-inactivating mutant (E71A). In the present study, we used mutants that did not harbor the E71A mutation, and showed that the electrostatic state of the CPD influences the inactivation gate. Three novel CPD mutants were generated in which some negatively charged amino acids were replaced with neutral amino acids. These CPD mutants conducted K+, but showed various inactivation properties. Mutants carrying the D149N mutation showed high open probability and slow inactivation, whereas those without the D149N mutation showed low open probability and fast inactivation, similar to wild-type KcsA. In addition, mutants with D149N showed poor K+ selectivity, and permitted Na+ to flow. These results indicated that electrostatic changes in the CPD by D149N mutation triggered the loss of fast inactivation and changes in the conformation of selectivity filter. Additionally, the loss of fast inactivation induced by D149N was reversed by R153A mutation, suggesting that not only the electrostatic state of D149, but also that of R153 affects inactivation.
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Affiliation(s)
- Minako Hirano
- Bio Photonics Laboratory, The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsu Nishi-ku, Hamamatsu, Shizuoka 431-1202, Japan.
| | - Toru Ide
- Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka Kita-ku, Okayama-shi, Okayama 700-8530, Japan
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46
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Zimmermann I, Egloff P, Hutter CA, Arnold FM, Stohler P, Bocquet N, Hug MN, Huber S, Siegrist M, Hetemann L, Gera J, Gmür S, Spies P, Gygax D, Geertsma ER, Dawson RJ, Seeger MA. Synthetic single domain antibodies for the conformational trapping of membrane proteins. eLife 2018; 7:34317. [PMID: 29792401 PMCID: PMC5967865 DOI: 10.7554/elife.34317] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 05/07/2018] [Indexed: 12/13/2022] Open
Abstract
Mechanistic and structural studies of membrane proteins require their stabilization in specific conformations. Single domain antibodies are potent reagents for this purpose, but their generation relies on immunizations, which impedes selections in the presence of ligands typically needed to populate defined conformational states. To overcome this key limitation, we developed an in vitro selection platform based on synthetic single domain antibodies named sybodies. To target the limited hydrophilic surfaces of membrane proteins, we designed three sybody libraries that exhibit different shapes and moderate hydrophobicity of the randomized surface. A robust binder selection cascade combining ribosome and phage display enabled the generation of conformation-selective, high affinity sybodies against an ABC transporter and two previously intractable human SLC transporters, GlyT1 and ENT1. The platform does not require access to animal facilities and builds exclusively on commercially available reagents, thus enabling every lab to rapidly generate binders against challenging membrane proteins.
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Affiliation(s)
- Iwan Zimmermann
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Pascal Egloff
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Cedric Aj Hutter
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Fabian M Arnold
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Peter Stohler
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Nicolas Bocquet
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Melanie N Hug
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Sylwia Huber
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Martin Siegrist
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Lisa Hetemann
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Jennifer Gera
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Samira Gmür
- University of Applied Sciences and Arts Northwestern Switzerland, Muttenz, Switzerland
| | - Peter Spies
- University of Applied Sciences and Arts Northwestern Switzerland, Muttenz, Switzerland
| | - Daniel Gygax
- University of Applied Sciences and Arts Northwestern Switzerland, Muttenz, Switzerland
| | - Eric R Geertsma
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Roger Jp Dawson
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Markus A Seeger
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
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47
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Li X, Sevillano N, La Greca F, Deis L, Liu YC, Deller MC, Mathews II, Matsui T, Cane DE, Craik CS, Khosla C. Structure-Function Analysis of the Extended Conformation of a Polyketide Synthase Module. J Am Chem Soc 2018; 140:6518-6521. [PMID: 29762030 DOI: 10.1021/jacs.8b02100] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Catalytic modules of assembly-line polyketide synthases (PKSs) have previously been observed in two very different conformations-an "extended" architecture and an "arch-shaped" architecture-although the catalytic relevance of neither has been directly established. By the use of a fully human naïve antigen-binding fragment (Fab) library, a high-affinity antibody was identified that bound to the extended conformation of a PKS module, as verified by X-ray crystallography and tandem size-exclusion chromatography-small-angle X-ray scattering (SEC-SAXS). Kinetic analysis proved that this antibody-stabilized module conformation was fully competent for catalysis of intermodular polyketide chain translocation as well as intramodular polyketide chain elongation and functional group modification of a growing polyketide chain. Thus, the extended conformation of a PKS module is fully competent for all of its essential catalytic functions.
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Affiliation(s)
| | - Natalia Sevillano
- Department of Pharmaceutical Chemistry , University of California San Francisco , San Francisco , California 94158 , United States
| | - Florencia La Greca
- Department of Pharmaceutical Chemistry , University of California San Francisco , San Francisco , California 94158 , United States
| | | | | | - Marc C Deller
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - David E Cane
- Department of Chemistry , Box H, Brown University , Providence , Rhode Island 02912-9108 , United States
| | - Charles S Craik
- Department of Pharmaceutical Chemistry , University of California San Francisco , San Francisco , California 94158 , United States
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48
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Niitsu A, Heal JW, Fauland K, Thomson AR, Woolfson DN. Membrane-spanning α-helical barrels as tractable protein-design targets. Philos Trans R Soc Lond B Biol Sci 2018. [PMID: 28630153 DOI: 10.1098/rstb.2016.0213] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The rational (de novo) design of membrane-spanning proteins lags behind that for water-soluble globular proteins. This is due to gaps in our knowledge of membrane-protein structure, and experimental difficulties in studying such proteins compared to water-soluble counterparts. One limiting factor is the small number of experimentally determined three-dimensional structures for transmembrane proteins. By contrast, many tens of thousands of globular protein structures provide a rich source of 'scaffolds' for protein design, and the means to garner sequence-to-structure relationships to guide the design process. The α-helical coiled coil is a protein-structure element found in both globular and membrane proteins, where it cements a variety of helix-helix interactions and helical bundles. Our deep understanding of coiled coils has enabled a large number of successful de novo designs. For one class, the α-helical barrels-that is, symmetric bundles of five or more helices with central accessible channels-there are both water-soluble and membrane-spanning examples. Recent computational designs of water-soluble α-helical barrels with five to seven helices have advanced the design field considerably. Here we identify and classify analogous and more complicated membrane-spanning α-helical barrels from the Protein Data Bank. These provide tantalizing but tractable targets for protein engineering and de novo protein design.This article is part of the themed issue 'Membrane pores: from structure and assembly, to medicine and technology'.
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Affiliation(s)
- Ai Niitsu
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Jack W Heal
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Kerstin Fauland
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Andrew R Thomson
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Derek N Woolfson
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK .,School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.,BrisSynBio, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK
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49
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Abstract
Crystallization of dual-topology fluoride (Fluc) channels requires small, soluble crystallization chaperones known as monobodies, which act as primary crystal lattice contacts. Previous structures of Flucs have been solved in the presence of monobodies that inhibit fluoride currents in single-channel electrophysiological recordings. These structures have revealed two-fold symmetric, doubly bound arrangements, with one monobody on each side of the membrane. The combined electrophysiological and structural observations raise the possibility that chaperone binding allosterically closes the channel, altering the structure from its conducting form. To address this, we identify and solve the structure with a different monobody that only partially blocks fluoride currents. The structure of the channel-monobody complex is asymmetric, with monobody bound to one side of the channel only. The channel conformation is nearly identical on the bound and uncomplexed sides, and to all previously solved structures, providing direct structural evidence that monobody binding does not induce local structural changes. Inhibitory crystallization chaperones bind on each side of the membrane Crystal structure of channel with one side free of chaperone binding S8 chaperone-bound channel is competent for fluoride transport Chaperones inhibit channels via a “cork-in-bottle” mechanism of physical occlusion
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50
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Hardy D, Desuzinges Mandon E, Rothnie AJ, Jawhari A. The yin and yang of solubilization and stabilization for wild-type and full-length membrane protein. Methods 2018; 147:118-125. [PMID: 29477816 DOI: 10.1016/j.ymeth.2018.02.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 02/12/2018] [Accepted: 02/18/2018] [Indexed: 11/16/2022] Open
Abstract
Membrane proteins (MP) are stable in their native lipid environment. To enable structural and functional investigations, MP need to be extracted from the membrane. This is a critical step that represents the main obstacle for MP biochemistry and structural biology. General guidelines and rules for membrane protein solubilization remain difficult to establish. This review aims to provide the reader with a comprehensive overview of the general concepts of MP solubilization and stabilization as well as recent advances in detergents innovation. Understanding how solubilization and stabilization are intimately linked is key to facilitate MP isolation toward fundamental structural and functional research as well as drug discovery applications. How to manage the tour de force of destabilizing the lipid bilayer and stabilizing MP at the same time is the holy grail of successful isolation and investigation of such a delicate and fascinating class of proteins.
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Affiliation(s)
- David Hardy
- CALIXAR, 60 Avenue Rockefeller, 69008 Lyon, France; Life & Health Sciences, Aston University, Birmingham B4 7ET, UK
| | | | - Alice J Rothnie
- Life & Health Sciences, Aston University, Birmingham B4 7ET, UK
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