Co-operative gating interactions in the yeast TOK1 K+ channel

Lead Research Organisation: University of Glasgow
Department Name: Institute of Biomedical & Life Sciences

Abstract

K+ channels play major roles in all living cells, providing a pore, or pathway for K+ ion movements across membranes. How these channels are constructed and the mechanisms by which they regulate (gate) the flow of K+ through their pores is a field of intense research. We know now that the pores of all K+ channels comprise four protein domains, each with a pore loop and two, flanking transmembrane helices. Gating of these channels has generally been thought to arise from independent protein conformational changes within each domain that contribute to opening the pore. The yeast K+ channel TOK1 is gated both by voltage and by extracellular K+. Surprisingly, we recently uncovered evidence of long-distance interactions between putative K+-binding sites associated with each pore loop. The results identify an unanticipated co-operativity between adjacent pore domains and, thus, should provide new insights into the gating of these channels. An extension to the current project will enable us to systematically explore these interactions and their implications for the molecular functioning of the TOK1 K+ channel.

Technical Summary

Understanding the molecular mechanisms of gating in voltage-gated K+ channels remains a major issue in biology. The combination of structural, molecular and cellular methods to their analysis has already yielded some remarkable insights into these processes. We know now that the pores of all K+ channels comprise four protein domains, each with a pore loop and two, flanking transmembrane helices. Gating of these channels has generally been thought to arise from independent conformational changes within each domain that contribute to opening the pore. The yeast K+ channel TOK1 is gated both by voltage and by extracellular K+. Surprisingly, we recently uncovered evidence of long-distance interactions between putative K+-binding sites associated with each pore loop. We had demonstrated previously that the K+-sensitivity of TOK1 is mediated by two, kinetically separate K+ gates with different [K+] dependencies and, apparently, paired K+-binding sites on the outer surface of each pore domain. Quite unexpectly, our studies now have uncovered long-range interactions between K+-binding sites, demonstrating a co-operativity between pore domains in TOK1 channel gating. These data offer the first substantive evidence of a synergy between pore domains in a K+ channel, and are likely to yield important clues to the mechanics of gating in TOK1 and, plausibly, in other K+ channels. Because extracellular K+ clearly interacts with voltage-mediated gating in these channels, we now have a powerful tool with which both to manipulate gating and to probe the associated protein conformations. We will extend our present studies to mapping the cross-interacting domains that affect gating synergistically. A key advantage for these studies will be our use of double mutants that 'rescue' quasi-wild-type characteristics. Experiments will compare the the effects of single and double mutations on synergistic and/or compensatory effects in gating. We will assess the requirement for the intact protein backbone in gating synergy between the pores. Finally, we will examine potential for cross-interaction between TOK1 pore domains on separate polypeptide chains. These experiments will identify residues are critical for cross-interaction between the pore domains and should establish the scope and relationship(s) in pore domain interactions for TOK1 gating.

Publications

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Alpi A (2007) Plant neurobiology: no brain, no gain? in Trends in plant science

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Armengaud P (2009) EZ-Rhizo: integrated software for the fast and accurate measurement of root system architecture. in The Plant journal : for cell and molecular biology

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Bassham DC (2008) SNAREs: cogs and coordinators in signaling and development. in Plant physiology

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Blatt M (2007) Rhythms in Plants

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Blatt MR (2018) New Faces behind the Scenes. in Plant physiology

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Blatt MR (2017) Small Pores with a Big Impact. in Plant physiology

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Blatt MR (2018) Plant Physiology Launches Associate Features Editors. in Plant physiology

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Caesar K (2011) A fast brassinolide-regulated response pathway in the plasma membrane of Arabidopsis thaliana. in The Plant journal : for cell and molecular biology

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Campanoni P (2007) Membrane trafficking and polar growth in root hairs and pollen tubes. in Journal of experimental botany

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Campanoni P (2007) A generalized method for transfecting root epidermis uncovers endosomal dynamics in Arabidopsis root hairs. in The Plant journal : for cell and molecular biology

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Chen Z (2009) Systems analysis of membrane transport and homeostasis in stomatal guard cells in Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

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Chen ZH (2017) Molecular Evolution of Grass Stomata. in Trends in plant science

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Eisenach C (2009) The role of membrane and Ion channel trafficking in stomatal stress responses in Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

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Feroz H (2018) Light-Driven Chloride Transport Kinetics of Halorhodopsin. in Biophysical journal

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Feroz H (2021) Liposome-based measurement of light-driven chloride transport kinetics of halorhodopsin. in Biochimica et biophysica acta. Biomembranes

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Grefen C (2008) SNAREs--molecular governors in signalling and development. in Current opinion in plant biology

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Grefen C (2011) Ion transport, membrane traffic and cellular volume control. in Current opinion in plant biology

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Jezek M (2019) A constraint-relaxation-recovery mechanism for stomatal dynamics. in Plant, cell & environment

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Johansson I (2006) External K+ modulates the activity of the Arabidopsis potassium channel SKOR via an unusual mechanism. in The Plant journal : for cell and molecular biology

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Lefoulon C (2021) The bare necessities of plant K+ channel regulation. in Plant physiology

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Liao X (2019) A FRET method for investigating dimer/monomer status and conformation of the UVR8 photoreceptor. in Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology

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Riedelsberger J (2017) Editorial: Roots-The Hidden Provider. in Frontiers in plant science

 
Title EZ-Rhizo 
Description Computer software tool for quantitative measurement and analysis of root growth/development 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2010 
Provided To Others? Yes  
Impact Multiple publications from my own research group and research groups worldwide Online distribution has been accessed through the laboratory website with site views at a rate of >500 per month 
URL http://psrg.org.uk
 
Title Henry 
Description Software for electrophysiology and imaging data aquisition and analysis 
Type Of Material Technology assay or reagent 
Provided To Others? Yes  
Impact Multiple publications from my own research group and research groups worldwide Online distribution has been accessed through the laboratory website with site views at a rate of >500 per month 
URL http://psrg.org.uk
 
Title Software tools for electrophysiology and imaging 
Description The laboratory continues to develop and refine software/hardware tools for data acquisition and analysis relevant to electrophysiology, single-cell imaging and analysis. These activities are long-standing and open-ended, and develop in line with the current research activities and needs of the laboratory. All software and related packages are made freely available to the research community through the laboratory website at psrg.org.uk 
Type Of Material Technology assay or reagent 
Provided To Others? Yes  
Impact The various software tools and packages have furthered the research activities of the laboratory since the 1990s and continue to provide key support and drivers for advancing much of current research. These tools and packages are disseminated, on average, to over 100 laboratories per year. 
URL http://psrg.org.uk
 
Title EZ-Rhizo 
Description Software for quantitative trait analysis and acquisition for root growth/development 
Type Of Material Database/Collection of data 
Year Produced 2010 
Provided To Others? Yes  
Impact Multiple publications from my own research group and research groups worldwide Online distribution has been accessed through the laboratory website with site views at a rate of >500 per month 
URL http://psrg.org.uk
 
Title Henry 
Description Software package for electrophysiology and imaging data acquisition and analysis 
Type Of Material Data handling & control 
Provided To Others? Yes  
Impact Multiple publications from my own research group and research groups worldwide Online distribution has been accessed through the laboratory website with site views at a rate of >500 per month 
URL http://psrg.org.uk
 
Title OnGuard 
Description Quantitative systems biology modelling of cellular transport and homeostasis 
Type Of Material Computer model/algorithm 
Year Produced 2012 
Provided To Others? Yes  
Impact Multiple publications from my own research group and research groups worldwide Online distribution has been accessed through the laboratory website with site views at a rate of >500 per month 
URL http://psrg.org.uk
 
Description PBL 
Organisation Plant Bioscience Limited Technology
Country United Kingdom 
Sector Private 
PI Contribution IPR on ABA receptor technology and ABA signalling
Collaborator Contribution Funding related to IPR on ABA receptor technology and ABA signalling
Impact Multiple outcomes in publications and industrial contacts
 
Description PSG 
Organisation POSCO - South Korea
Country Korea, Republic of 
Sector Private 
PI Contribution Base support for meetings and exchange of materials
Collaborator Contribution Base support for meetings and exchange of materials
Impact Base support for meetings and exchange of materials
 
Title Software tools and packages for electrophysiology and imaging 
Description The laboratory continues to develop and refine software/hardware tools for data acquisition and analysis relevant to electrophysiology, single-cell imaging and analysis. These activities are long-standing and open-ended, and develop in line with the current research activities and needs of the laboratory. All software and related packages are made freely available to the research community through the laboratory website at psrg.org.uk 
Type Of Technology Software 
Impact The various software tools and packages have furthered the research activities of the laboratory since the 1990s and continue to provide key support and drivers for advancing much of current research. These tools and packages are disseminated, on average, to over 100 laboratories per year. 
URL http://psrg.org.uk
 
Description International online services 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Prof. Blatt and members of his laboratory have contributed to various media events over the years, including online interview contributions (e.g. People behind the Science, a US-based media program)
Year(s) Of Engagement Activity Pre-2006,2006,2008,2011,2015,2016,2017,2018
 
Description Invited presentations 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I regularly speak to audiences, from small groups (5-20) to large audiences (>1000) in a variety of settings. In addition to teaching and extramural activities associated with the university, I also speak on invitation to national and international groups a number of times each year and in a variety of settings, academic as well as public. I also reach audiences through short video presentations mounted on the web, these primarily via my laboratory website and the ASPB websites. Anyone reading this entry is welcome to visit these sites to learn more.

The impacts arising from my presentations are varied. For example, a common consequence of my speaking in academic settings is to attract potential researchers to visit my laboratory and, frequently, to interest potential collaborators and students/postdocs to my research group. At scientific meetings, my talks often attract interest also from researchers interested in the various tools and materials that my research has produced, including the various vector systems and software packages that I
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018
URL http://psrg.org.uk
 
Description Schools and displays 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact As these were multiple events, this question is not informative or useful. Participants varied from numbers in the tens to several thousands

Extensive training of participating laboratory members as well as broad scope reach to schools and communities, in the case of the GCC science days to the west of Scotland and in the case of the IFPD activities to audiences within and outside the UK
Year(s) Of Engagement Activity 2010,2011,2012,2013,2014,2015,2016,2017,2018
URL http://psrg.org.uk
 
Description Teaching Tools 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Schools
Results and Impact The PI has supported the editor in developing these tools since their inception in 2009 and has contributed to recent tools relating to membranes and transport education

The Tool received an international award in 2010 for excellence in education and has an acknowledged takeup worldwide in over 3000 institutions
Year(s) Of Engagement Activity 2009,2010,2011,2012,2013,2014,2015,2016,2017,2018
URL http://psrg.org.uk
 
Description Teaching Tools 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Schools
Results and Impact The PI has supported the editor in developing these tools since their inception in 2009 and has contributed to recent tools relating to membranes and transport education

The Tool received an international award in 2010 for excellence in education and has an acknowledged takeup worldwide in over 3000 institutions
Year(s) Of Engagement Activity 2009,2010,2011,2012,2013,2014,2015,2016,2017,2018
URL http://psrg.org.uk