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Lin JL, Chang Y, Tewari D, Cowgill J, Chanda B. Mapping the contribution of the C-linker domain to gating polarity in CNBD channels. Biophys J 2024; 123:2176-2184. [PMID: 38678368 PMCID: PMC11309966 DOI: 10.1016/j.bpj.2024.04.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 03/23/2024] [Accepted: 04/22/2024] [Indexed: 04/29/2024] Open
Abstract
Ion channels of the cyclic nucleotide-binding domain (CNBD) family play a crucial role in the regulation of key biological processes, such as photoreception and pacemaking activity in the heart. These channels exhibit high sequence and structural similarity but differ greatly in their functional responses to membrane potential. The CNBD family includes hyperpolarization-activated ion channels and depolarization-activated ether-à-go-go channels. Structural and functional studies show that the differences in the coupling interface between these two subfamilies' voltage-sensing domain and pore domain may underlie their differential response to membrane polarity. However, other structural components may also contribute to defining the polarity differences in activation. Here, we focus on the role of the C-terminal domain, which interacts with elements in both the pore and voltage-sensing domains. By generating a series of chimeras involving the C-terminal domain derived from distant members of the CNBD family, we find that the nature of the C-termini profoundly influences the gating polarity of these ion channels. Scanning mutagenesis of the C-linker region, a helix-turn-helix motif connecting the pore helix to the CNBD, reveals that residues at the intersubunit interface between the C-linkers are crucial for hyperpolarization-dependent activation. These findings highlight the unique and unexpected role of the intersubunit interface of the C-linker region in regulating the gating polarity of voltage-gated ion channels.
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Affiliation(s)
- Jenna L Lin
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Graduate Program in Biochemistry, Biophysics, & Structural Biology, Washington University School of Medicine, St. Louis, Missouri
| | - Yongchang Chang
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Debanjan Tewari
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - John Cowgill
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Baron Chanda
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri.
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2
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Blatt MR. A charged existence: A century of transmembrane ion transport in plants. PLANT PHYSIOLOGY 2024; 195:79-110. [PMID: 38163639 PMCID: PMC11060664 DOI: 10.1093/plphys/kiad630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 11/01/2023] [Indexed: 01/03/2024]
Abstract
If the past century marked the birth of membrane transport as a focus for research in plants, the past 50 years has seen the field mature from arcane interest to a central pillar of plant physiology. Ion transport across plant membranes accounts for roughly 30% of the metabolic energy consumed by a plant cell, and it underpins virtually every aspect of plant biology, from mineral nutrition, cell expansion, and development to auxin polarity, fertilization, plant pathogen defense, and senescence. The means to quantify ion flux through individual transporters, even single channel proteins, became widely available as voltage clamp methods expanded from giant algal cells to the fungus Neurospora crassa in the 1970s and the cells of angiosperms in the 1980s. Here, I touch briefly on some key aspects of the development of modern electrophysiology with a focus on the guard cells of stomata, now without dispute the premier plant cell model for ion transport and its regulation. Guard cells have proven to be a crucible for many technical and conceptual developments that have since emerged into the mainstream of plant science. Their study continues to provide fundamental insights and carries much importance for the global challenges that face us today.
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Affiliation(s)
- Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
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3
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Nguyen TBA, Lefoulon C, Nguyen TH, Blatt MR, Carroll W. Engineering stomata for enhanced carbon capture and water-use efficiency. TRENDS IN PLANT SCIENCE 2023; 28:1290-1309. [PMID: 37423785 DOI: 10.1016/j.tplants.2023.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 05/29/2023] [Accepted: 06/02/2023] [Indexed: 07/11/2023]
Abstract
Stomatal pores facilitate gaseous exchange between the inner air spaces of the leaf and the atmosphere. As gatekeepers that balance CO2 entry for photosynthesis against transpirational water loss, they are a focal point for efforts to improve crop performance, especially in the efficiency of water use, within the changing global environment. Until recently, engineering strategies had focused on stomatal conductance in the steady state. These strategies are limited by the physical constraints of CO2 and water exchange such that gains in water-use efficiency (WUE) commonly come at a cost in carbon assimilation. Attention to stomatal speed and responsiveness circumvents these constraints and offers alternatives to enhancing WUE that also promise increases in carbon assimilation in the field.
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Affiliation(s)
- Thu Binh-Anh Nguyen
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Cecile Lefoulon
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Thanh-Hao Nguyen
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK.
| | - William Carroll
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
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4
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Li S, Wang Y, Wang C, Zhang Y, Sun D, Zhou P, Tian C, Liu S. Cryo-EM structure reveals a symmetry reduction of the plant outward-rectifier potassium channel SKOR. Cell Discov 2023; 9:67. [PMID: 37391403 PMCID: PMC10313817 DOI: 10.1038/s41421-023-00572-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 05/30/2023] [Indexed: 07/02/2023] Open
Affiliation(s)
- Siyu Li
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Joint Center for Biological Analytical Chemistry, Anhui Engineering Laboratory of Peptide Drug, Anhui Laboratory of Advanced Photonic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China
| | - Yuanxia Wang
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Joint Center for Biological Analytical Chemistry, Anhui Engineering Laboratory of Peptide Drug, Anhui Laboratory of Advanced Photonic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China
| | - Chenyang Wang
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Joint Center for Biological Analytical Chemistry, Anhui Engineering Laboratory of Peptide Drug, Anhui Laboratory of Advanced Photonic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China
| | - Yong Zhang
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Joint Center for Biological Analytical Chemistry, Anhui Engineering Laboratory of Peptide Drug, Anhui Laboratory of Advanced Photonic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China
| | - Demeng Sun
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Joint Center for Biological Analytical Chemistry, Anhui Engineering Laboratory of Peptide Drug, Anhui Laboratory of Advanced Photonic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China
| | - Peng Zhou
- School of Life Science, Hefei Normal University, Hefei, Anhui, China.
| | - Changlin Tian
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Joint Center for Biological Analytical Chemistry, Anhui Engineering Laboratory of Peptide Drug, Anhui Laboratory of Advanced Photonic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China.
- The Anhui Provincial Key Laboratory of High Magnetic Resonance Image, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China.
| | - Sanling Liu
- Department of Endocrinology, Institute of Endocrine and Metabolic Diseases, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Joint Center for Biological Analytical Chemistry, Anhui Engineering Laboratory of Peptide Drug, Anhui Laboratory of Advanced Photonic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China.
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Horaruang W, Klejchová M, Carroll W, Silva-Alvim FAL, Waghmare S, Papanatsiou M, Amtmann A, Hills A, Alvim JC, Blatt MR, Zhang B. Engineering a K + channel 'sensory antenna' enhances stomatal kinetics, water use efficiency and photosynthesis. NATURE PLANTS 2022; 8:1262-1274. [PMID: 36266492 DOI: 10.1038/s41477-022-01255-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 09/12/2022] [Indexed: 06/16/2023]
Abstract
Stomata of plant leaves open to enable CO2 entry for photosynthesis and close to reduce water loss via transpiration. Compared with photosynthesis, stomata respond slowly to fluctuating light, reducing assimilation and water use efficiency. Efficiency gains are possible without a cost to photosynthesis if stomatal kinetics can be accelerated. Here we show that clustering of the GORK channel, which mediates K+ efflux for stomatal closure in the model plant Arabidopsis, arises from binding between the channel voltage sensors, creating an extended 'sensory antenna' for channel gating. Mutants altered in clustering affect channel gating to facilitate K+ flux, accelerate stomatal movements and reduce water use without a loss in biomass. Our findings identify the mechanism coupling channel clustering with gating, and they demonstrate the potential for engineering of ion channels native to the guard cell to enhance stomatal kinetics and improve water use efficiency without a cost in carbon fixation.
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Affiliation(s)
- Wijitra Horaruang
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
- Faculty of Science and Arts, Burapha University, Chanthaburi Campus, Chanthaburi, Thailand
| | - Martina Klejchová
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - William Carroll
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | | | - Sakharam Waghmare
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Maria Papanatsiou
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Anna Amtmann
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Adrian Hills
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Jonas Chaves Alvim
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK.
| | - Ben Zhang
- School of Life Sciences, Shanxi University, Taiyuan City, China
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Structural basis for the activity regulation of a potassium channel AKT1 from Arabidopsis. Nat Commun 2022; 13:5682. [PMID: 36167696 PMCID: PMC9515098 DOI: 10.1038/s41467-022-33420-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 09/16/2022] [Indexed: 11/25/2022] Open
Abstract
The voltage-gated potassium channel AKT1 is responsible for primary K+ uptake in Arabidopsis roots. AKT1 is functionally activated through phosphorylation and negatively regulated by a potassium channel α-subunit AtKC1. However, the molecular basis for the modulation mechanism remains unclear. Here we report the structures of AKT1, phosphorylated-AKT1, a constitutively-active variant, and AKT1-AtKC1 complex. AKT1 is assembled in 2-fold symmetry at the cytoplasmic domain. Such organization appears to sterically hinder the reorientation of C-linkers during ion permeation. Phosphorylated-AKT1 adopts an alternate 4-fold symmetric conformation at cytoplasmic domain, which indicates conformational changes associated with symmetry switch during channel activation. To corroborate this finding, we perform structure-guided mutagenesis to disrupt the dimeric interface and identify a constitutively-active variant Asp379Ala mediates K+ permeation independently of phosphorylation. This variant predominantly adopts a 4-fold symmetric conformation. Furthermore, the AKT1-AtKC1 complex assembles in 2-fold symmetry. Together, our work reveals structural insight into the regulatory mechanism for AKT1. Arabidopsis thaliana potassium channel AKT1 is responsible for primary K + uptake from soil, which is functionally activated through phosphorylation and negatively regulated by an α-subunit AtKC1. Here, the authors report the structures of AKT1 at different states, revealing a 2- fold to 4-fold symmetry switch at cytoplasmic domain associated with AKT1 activity regulation.
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