Atomic scale movement of the voltage-sensing region in a potassium channel measured via spectroscopy

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Voltage-gated ion channels are transmembrane proteins that are essential for nerve impulses and regulate ion flow across cell membranes in response to changes in membrane potential. They are made up of four homologous domains or subunits, each of which contains six transmembrane segments1,2. Studies of potassium channels have shown that the second (S2) and fourth (S4) segments contain several charged residues, which sense changes in voltage and form part of the voltage sensor3,4,5. Although these regions clearly undergo conformational changes in response to voltage6,7,8,9,10, little is known about the nature of these changes because voltage-dependent distance changes have not been measured. Here we use lanthanide-based resonance energy transfer11,12 to measure distances between Shaker potassium channel subunits at specific residues. Voltage-dependent distance changes of up to 3.2 Å were measured at several sites near the S4 segment. These movements directly correlated with electrical measurements of the voltage sensor, establishing the link between physical changes and electrical charge movement. Measured distance changes suggest that the region associated with the S4 segment undergoes a rotation and possible tilt, rather than a large transmembrane movement, in response to voltage. These results demonstrate the first in situ measurement of atomic scale movement in a transmembrane protein.

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Figure 1: Labelling methodology and characteristics of ion channel.
Figure 2: Transmembrane topology of the Shaker potassium channel.
Figure 3: Voltage-dependent distance changes at residue S346C and correlation to gating charge movement.
Figure 4: Distance changes at three successive residues in the S3–S4 linker.
Figure 5: Translation versus rotation models of S4 movement.


  1. 1

    Noda,M. et al. Primary structure of the Electrophorus electricus sodium channel deduced from cDNA sequence. Nature 312, 121–127 (1984).

  2. 2

    Tempel,B. L., Papazian,D. M., Schwarz,T. L., Jan,Y. L. & Jan,L. Y. Sequence of a probable potassium channel component encoded at Shaker locus of Drosophila. Science 237, 770–775 (1987).

  3. 3

    Armstrong,C. M. & Bezanilla,F. Currents related to the movement of the gating particles of sodium channels. Nature 242, 459–461 (1973).

  4. 4

    Seoh,S. A., Sigg,D., Papazian,D. M. & Bezanilla,F. Voltage-sensing residues in the S2 and S4 segments of the Shaker K+ channel. Neuron 16, 1159–1167 (1996).

  5. 5

    Aggarwal,S. K. & MacKinnon,R. Contribution of the S4 segment to gating charge in the Shaker K+ channel. Neuron 16, 1169–1177 (1996).

  6. 6

    Yang,N. & Horn,R. Evidence for voltage-dependent S4 movement in sodium channels. Neuron 15, 213–218 (1995).

  7. 7

    Larsson,H. P., Baker,O. S., Dhillon,D. S. & Isacoff,E. Y. Transmembrane movement of the Shaker K+ channel S4. Neuron 16, 387–397 (1996).

  8. 8

    Starace,D. M., Stefani,E. & Bezanilla,F. Voltage-dependent proton transport by the voltage sensor of the Shaker K+ channel. Neuron 19, 1319–1327 (1997).

  9. 9

    Mannuzzu,L. M., Moronne,M. M. & Isacoff,E. Y. Direct physical measure of conformational rearrangement underlying potassium channel gating. Science 271, 213–216 (1996).

  10. 10

    Cha,A. & Bezanilla,F. Characterizing voltage-dependent conformational changes in the Shaker K+ channel with fluorescence. Neuron 19, 1127–1140 (1997).

  11. 11

    Selvin,P. R. & Hearst,J. E. Luminescence energy transfer using a terbium chelate: improvements on fluorescence energy transfer. Proc. Natl Acad. Sci. USA 91, 10024–10028 (1994).

  12. 12

    Selvin,P. R., Rana,T. M. & Hearst,J. E. Luminescence resonance energy transfer. J. Am. Chem. Soc. 116, 6029–6030 (1994).

  13. 13

    Xiao,M. et al. Conformational changes between the active-site and regulatory light chain of myosin as determined by luminescence resonance energy transfer: the effect of nucleotides and actin. Proc. Natl Acad. Sci. 95, 15309–15314 (1998).

  14. 14

    Doyle,D. A. et al. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science 280, 69–77 (1998).

  15. 15

    Gross,A., Columbus,L., Hideg,K., Altenbach,C. & Hubbell,W. L. Structure of the KcsA potassium channel from Streptomyces lividans: A site-directed spin labeling study of the second transmembrane segment. Biochemistry 38, 10324–10335 (1999).

  16. 16

    MacKinnon,R., Cohen,S.L., Kuo,A., Lee,A. & Chait,B. T. Structural conservation in prokaryotic and eukaryotic potassium channels. Science 280, 106–109 (1998).

  17. 17

    Durell,S. R. & Guy,H. R. Atomic scale structure and functional models of voltage-gated potassium channels. Biophys. J. 62, 238–247 (1992).

  18. 18

    Selvin,P. R. Fluorescence resonance energy transfer. Methods Enzymol. 246, 300–344 (1995).

  19. 19

    Chen,J. & Selvin,P. R. Thiol-reactive luminescent chelates of terbium and europium. Bioconjugate Chem. 10, 311–315 (1999).

  20. 20

    Cha,A. & Bezanilla,F. Structural implications of fluorescence quenching in the Shaker K+ channel. J. Gen. Phys. 112, 391–408 (1998).

  21. 21

    Bezanilla,F., Perozo,E. & Stefani,E. Gating of Shaker K+ channels: II. The components of gating currents and a model of channel activation. Biophys. J. 66, 1011–1021 (1994).

  22. 22

    Smith-Maxwell,C. J., Ledwell,J. L. & Aldrich,R. W. Uncharged S4 residues and cooperativity in voltage-dependent potassium channel activation. J. Gen. Phys. 111, 421–439 (1998).

  23. 23

    Schoppa,N. E. & Sigworth,F. Activation of Shaker potassium channels. III. An activation gating model for wild-type and V2 mutant channels. J. Gen. Phys. 111, 313–342 (1998).

  24. 24

    Selvin,P. R., Jancarik,J., Li,M. & Hung,L. W. Crystal structure and spectroscopic characterization of a luminescent europium chelate. Inorg. Chem. 35, 700–705 (1996).

  25. 25

    Bezanilla,F. The voltage sensor in voltage dependent ion channels. Physiol. Rev. (in the press).

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This work was supported by NIH grants to F.B. and P.R.S., the Hagiwara Chair funds to F.B., and from Research Corporation to P.R.S. A.C. was also supported by UCLA Medical Scientist Training Program and a National Research Service Award from National Institute of Mental Health. G.E.S. was supported by a National Research Service Award in Molecular Biophysics. We thank A. Gross, for his involvement in preliminary FRET results, and J. Chen, for synthesis of maleimide terbium chelates. We also thank the members of the Bezanilla lab for their support.

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Correspondence to Francisco Bezanilla.

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Cha, A., Snyder, G., Selvin, P. et al. Atomic scale movement of the voltage-sensing region in a potassium channel measured via spectroscopy. Nature 402, 809–813 (1999) doi:10.1038/45552

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