Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Structure of the carboxy-terminal region of a KCNH channel

Abstract

The KCNH family of ion channels, comprising ether-à-go-go (EAG), EAG-related gene (ERG), and EAG-like (ELK) K+-channel subfamilies, is crucial for repolarization of the cardiac action potential1, regulation of neuronal excitability2 and proliferation of tumour cells3. The carboxy-terminal region of KCNH channels contains a cyclic-nucleotide-binding homology domain (CNBHD) and C-linker that couples the CNBHD to the pore4. The C-linker/CNBHD is essential for proper function and trafficking of ion channels in the KCNH family5,6,7,8,9. However, despite the importance of the C-linker/CNBHD for the function of KCNH channels, the structural basis of ion-channel regulation by the C-linker/CNBHD is unknown. Here we report the crystal structure of the C-linker/CNBHD of zebrafish ELK channels at 2.2-Å resolution. Although the overall structure of the C-linker/CNBHD of ELK channels is similar to the cyclic-nucleotide-binding domain (CNBD) structure of the related hyperpolarization-activated cyclic-nucleotide-modulated (HCN) channels10, there are marked differences. Unlike the CNBD of HCN, the CNBHD of ELK displays a negatively charged electrostatic profile that explains the lack of binding and regulation of KCNH channels by cyclic nucleotides4,11. Instead of cyclic nucleotide, the binding pocket is occupied by a short β-strand. Mutations of the β-strand shift the voltage dependence of activation to more depolarized voltages, implicating the β-strand as an intrinsic ligand for the CNBHD of ELK channels. In both ELK and HCN channels the C-linker is the site of virtually all of the intersubunit interactions in the C-terminal region. However, in the zebrafish ELK structure there is a reorientation in the C-linker so that the subunits form dimers instead of tetramers, as observed in HCN channels. These results provide a structural framework for understanding the regulation of ion channels in the KCNH family by the C-linker/CNBHD and may guide the design of specific drugs.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Topology and electrophysiological properties of zebrafish ELK channels.
Figure 2: Structure of the C-linker/CNBHD.
Figure 3: Structural comparison of the C-linker regions and quaternary arrangement of the C-linker/CNBHDs of zebrafish ELK and HCN2 channels.

Accession codes

Primary accessions

Protein Data Bank

Data deposits

Atomic coordinates and structure factors for the reported crystal structures have been deposited with the Protein Data Bank under accession codes 3UKN, 3UKT and 3UKV (see Supplementary Table 1 for identifications).

References

  1. Sanguinetti, M. C. & Tristani-Firouzi, M. hERG potassium channels and cardiac arrhythmia. Nature 440, 463–469 (2006)

    Article  ADS  CAS  Google Scholar 

  2. Zhang, X. et al. Deletion of the potassium channel Kv12.2 causes hippocampal hyperexcitability and epilepsy. Nature Neurosci. 13, 1056–1058 (2010)

    Article  CAS  Google Scholar 

  3. Camacho, J. Ether à go-go potassium channels and cancer. Cancer Lett. 233, 1–9 (2006)

    Article  CAS  Google Scholar 

  4. Ganetzky, B., Robertson, G. A., Wilson, G. F., Trudeau, M. C. & Titus, S. A. The Eag family of K+ channels in Drosophila and mammals. Ann. NY Acad. Sci. 868, 356–369 (1999)

    Article  ADS  CAS  Google Scholar 

  5. Al-Owais, M., Bracey, K. & Wray, D. Role of intracellular domains in the function of the herg potassium channel. Eur. Biophys. J. 38, 569–576 (2009)

    Article  CAS  Google Scholar 

  6. Stevens, L., Ju, M. & Wray, D. Roles of surface residues of intracellular domains of heag potassium channels. Eur. Biophys. J. 38, 523–532 (2009)

    Article  CAS  Google Scholar 

  7. Gustina, A. S. & Trudeau, M. C. hERG potassium channel gating is mediated by N- and C-terminal region interactions. J. Gen. Physiol. 137, 315–325 (2011)

    Article  CAS  Google Scholar 

  8. Muskett, F. W. et al. Mechanistic insight into human ether-à-go-go-related gene (hERG) K+ channel deactivation gating from the solution structure of the EAG domain. J. Biol. Chem. 286, 6184–6191 (2011)

    Article  CAS  Google Scholar 

  9. Zhou, Z., Gong, Q., Epstein, M. L. & January, C. T. HERG channel dysfunction in human long QT syndrome. Intracellular transport and functional defects. J. Biol. Chem. 273, 21061–21066 (1998)

    Article  CAS  Google Scholar 

  10. Zagotta, W. N. et al. Structural basis for modulation and agonist specificity of HCN pacemaker channels. Nature 425, 200–205 (2003)

    Article  ADS  CAS  Google Scholar 

  11. Brelidze, T. I., Carlson, A. E. & Zagotta, W. N. Absence of direct cyclic nucleotide modulation of mEAG1 and hERG1 channels revealed with fluorescence and electrophysiological methods. J. Biol. Chem. 284, 27989–27997 (2009)

    Article  CAS  Google Scholar 

  12. Morais Cabral, J. H. et al. Crystal structure and functional analysis of the HERG potassium channel N terminus: a eukaryotic PAS domain. Cell 95, 649–655 (1998)

    Article  CAS  Google Scholar 

  13. Schonherr, R. & Heinemann, S. H. Molecular determinants for activation and inactivation of HERG, a human inward rectifier potassium channel. J. Physiol. (Lond.) 493, 635–642 (1996)

    Article  Google Scholar 

  14. Wang, J., Trudeau, M. C., Zappia, A. M. & Robertson, G. A. Regulation of deactivation by an amino terminal domain in human ether-à-go-go-related gene potassium channels. J. Gen. Physiol. 112, 637–647 (1998)

    Article  CAS  Google Scholar 

  15. Muskett, F. W. et al. Mechanistic insight into hERG K+ channel deactivation gating from the solution structure of the EAG domain. J. Biol. Chem. 286, 6184–6191 (2011)

    Article  CAS  Google Scholar 

  16. Li, Q. et al. NMR solution structure of the N-terminal domain of hERG and its interaction with the S4–S5 linker. Biochem. Biophys. Res. Commun. 403, 126–132 (2010)

    Article  CAS  Google Scholar 

  17. Ng, C. A. et al. The N-terminal tail of hERG contains an amphipathic α-helix that regulates channel deactivation. PLoS ONE 6, e16191 (2011)

    Article  ADS  CAS  Google Scholar 

  18. Craven, K. B. & Zagotta, W. N. CNG and HCN channels: two peas, one pod. Annu. Rev. Physiol. 68, 375–401 (2006)

    Article  CAS  Google Scholar 

  19. Brelidze, T. I., Carlson, A. E., Davies, D. R., Stewart, L. J. & Zagotta, W. N. Identifying regulators for EAG1 channels with a novel electrophysiology and tryptophan fluorescence based screen. PLoS ONE 5, e12523 (2010)

    Article  ADS  Google Scholar 

  20. Splawski, I. et al. Spectrum of mutations in long-QT syndrome genes. KVLQT1, HERG, SCN5A, KCNE1, and KCNE2 . Circulation 102, 1178–1185 (2000)

    Article  CAS  Google Scholar 

  21. Kawate, T. & Gouaux, E. Fluorescence-detection size-exclusion chromatography for precrystallization screening of integral membrane proteins. Structure 14, 673–681 (2006)

    Article  CAS  Google Scholar 

  22. Becchetti, A. et al. The functional properties of the human ether-à-go-go-like (HELK2) K+ channel. Eur. J. Neurosci. 16, 415–428 (2002)

    Article  Google Scholar 

  23. Engeland, B., Neu, A., Ludwig, J., Roeper, J. & Pongs, O. Cloning and functional expression of rat ether-à-go-go-like K+ channel genes. J. Physiol. (Lond.) 513, 647–654 (1998)

    Article  CAS  Google Scholar 

  24. Trudeau, M. C., Titus, S. A., Branchaw, J. L., Ganetzky, B. & Robertson, G. A. Functional analysis of a mouse brain Elk-type K+ channel. J. Neurosci. 19, 2906–2918 (1999)

    Article  CAS  Google Scholar 

  25. Zou, A. et al. Distribution and functional properties of human KCNH8 (Elk1) potassium channels. Am. J. Physiol. Cell Physiol. 285, C1356–C1366 (2003)

    Article  CAS  Google Scholar 

  26. Rehmann, H., Wittinghofer, A. & Bos, J. L. Capturing cyclic nucleotides in action: snapshots from crystallographic studies. Nature Rev. Mol. Cell Biol. 8, 63–73 (2007)

    Article  CAS  Google Scholar 

  27. Altieri, S. L. et al. Structural and energetic analysis of activation by a cyclic nucleotide binding domain. J. Mol. Biol. 381, 655–669 (2008)

    Article  CAS  Google Scholar 

  28. Clayton, G. M., Silverman, W. R., Heginbotham, L. & Morais-Cabral, J. H. Structural basis of ligand activation in a cyclic nucleotide regulated potassium channel. Cell 119, 615–627 (2004)

    Article  CAS  Google Scholar 

  29. Schunke, S., Stoldt, M., Lecher, J., Kaupp, U. B. & Willbold, D. Structural insights into conformational changes of a cyclic nucleotide-binding domain in solution from Mesorhizobium loti K1 channel. Proc. Natl Acad. Sci. USA 108, 6121–6126 (2011)

    Article  ADS  CAS  Google Scholar 

  30. Napolitano, C. et al. Genetic testing in the long QT syndrome: development and validation of an efficient approach to genotyping in clinical practice. J. Am. Med. Assoc. 294, 2975–2980 (2005)

    Article  CAS  Google Scholar 

  31. Guerrero, S. A., Hecht, H. J., Hofmann, B., Biebl, H. & Singh, M. Production of selenomethionine-labelled proteins using simplified culture conditions and generally applicable host/vector systems. Appl. Microbiol. Biotechnol. 56, 718–723 (2001)

    Article  CAS  Google Scholar 

  32. Collaborative Computation Project 4 The CCP4 suite: programs for protein crystallography. Acta Crystallogr. D 50, 760–763 (1994)

    Article  Google Scholar 

  33. Otwinowski, Z. & Minor, W. Processing X-ray diffraction data collected in oscillation mode. Methods Enzymol. 276, 307–326 (1997)

    Article  CAS  Google Scholar 

  34. Adams, P. D. et al. PHENIX: a comprehensive Python-based system for macromolecular structure solution. Acta Crystallogr. D 66, 213–221 (2010)

    Article  CAS  Google Scholar 

  35. Emsley, P. & Cowtan, K. Coot: model-building tools for molecular graphics. Acta Crystallogr. D 60, 2126–2132 (2004)

    Article  Google Scholar 

  36. Chen, V. B. et al. MolProbity: all-atom structure validation for macromolecular crystallography. Acta Crystallogr. D 66, 12–21 (2010)

    Article  CAS  Google Scholar 

  37. DeLano, W. L. The PyMOL molecular graphics system. http://www.pymol.org (DeLano Scientific, 2002)

  38. Huson, D. H. et al. Dendroscope: an interactive viewer for large phylogenetic trees. BMC Bioinformatics 8, 460 (2007)

    Article  Google Scholar 

  39. Baker, N. A., Sept, D., Joseph, S., Holst, M. J. & McCammon, J. A. Electrostatics of nanosystems: application to microtubules and the ribosome. Proc. Natl Acad. Sci. USA 98, 10037–10041 (2001)

    Article  ADS  CAS  Google Scholar 

Download references

Acknowledgements

We thank M. Munari, S. Camp, S. Cunnington and G. Sheridan for excellent technical assistance. We thank the beamline staff at the Advanced Light Source (ALS) and especially P. Zwart for help with data analysis. We also thank the members of the Zagotta laboratory for helpful discussions. This work was supported by the Howard Hughes Medical Institute, National Institutes of Health (NIH) grant R01 EY010329 (W.N.Z.) and NIH grant F32 HL095241 (A.E.C.). The Berkeley Center for Structural Biology is supported in part by the NIH, National Institute of General Medical Sciences and the Howard Hughes Medical Institute. The ALS is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02-05CH11231.

Author information

Authors and Affiliations

Authors

Contributions

T.I.B. and W.N.Z. conceived the experiments. T.I.B. performed the crystallographic experiments, and B.S. helped with the crystallographic data analysis. A.E.C. and W.N.Z. performed the electrophysiology experiments and data analysis. T.I.B. and W.N.Z. wrote the manuscript.

Corresponding author

Correspondence to William N. Zagotta.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-10 with legends, Supplementary Table 1, a Supplementary Discussion and additional references. This file was replaced on 18 April 2012 (PDF 6933 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Brelidze, T., Carlson, A., Sankaran, B. et al. Structure of the carboxy-terminal region of a KCNH channel. Nature 481, 530–533 (2012). https://doi.org/10.1038/nature10735

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature10735

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing