Contribution of the S4 Segment to Gating Charge in the Shaker K+ Channel

Voltage-activated ion channels respond to changes in membrane voltage by coupling the movement of charges to channel opening. A K+ channel-specific radioligand was designed and used to determine the origin of these gating charges in the Shaker K+ channel. Opening of a Shaker K+ channel is associated with a displacement of 13.6 electron charge units. Gating charge contributions were determined for six of the seven positive charges in the S4 segment, an unusual amino acid sequence in voltage-activated cation channels consisting of repeating basic residues at every third position. Charge-neutralizing mutations of the first four positive charges led to large decreases (approximately 4 electron charge units each) in the gating charge; however, the gating charge of Shaker delta 10, a Shaker K+ channel with 10 altered nonbasic residues in its S4 segment, was found to be identical to the wild-type channel. These findings show that movement of the NH2-terminal half but not the CO2H-terminal end of the S4 segment underlies gating charge, and that this portion of the S4 segment appears to move across the entire transmembrane voltage difference in association with channel activation.

[1]  W. Catterall,et al.  Molecular properties of voltage-sensitive sodium channels. , 1986, Annual review of biochemistry.

[2]  Engineering a uniquely reactive thiol into a cysteine-rich peptide. , 1994, Protein engineering.

[3]  A. VanDongen,et al.  A novel potassium channel with delayed rectifier properties isolated from rat brain by expression cloning , 1989, Nature.

[4]  Y. Palti,et al.  Charge displacements in a single potassium ion channel macromolecule during gating. , 1994, Biophysical journal.

[5]  R. MacKinnon,et al.  Purification and characterization of three inhibitors of voltage-dependent K+ channels from Leiurus quinquestriatus var. hebraeus venom. , 1994, Biochemistry.

[6]  H. Guy,et al.  Atomic scale structure and functional models of voltage-gated potassium channels. , 1992, Biophysical journal.

[7]  A. Aggarwal,et al.  Structure of Bam HI endonuclease bound to DNA: partial folding and unfolding on DNA binding. , 1995, Science.

[8]  A. Hodgkin,et al.  A quantitative description of membrane current and its application to conduction and excitation in nerve , 1952, The Journal of physiology.

[9]  H. Takeshima,et al.  Existence of distinct sodium channel messenger RNAs in rat brain , 1986, Nature.

[10]  H. Guy,et al.  Molecular model of the action potential sodium channel. , 1986, Proceedings of the National Academy of Sciences of the United States of America.

[11]  J. Tytgat,et al.  Subunit stoichiometry of a mammalian K+ channel determined by construction of multimeric cDNAs , 1992, Neuron.

[12]  T Hoshi,et al.  Biophysical and molecular mechanisms of Shaker potassium channel inactivation , 1990, Science.

[13]  E. Liman,et al.  Voltage-sensing residues in the S4 region of a mammalian K+ channel , 1991, Nature.

[14]  Y. Jan,et al.  Alteration of voltage-dependence of Shaker potassium channel by mutations in the S4 sequence , 1991, Nature.

[15]  R. Keynes,et al.  Kinetics and steady‐state properties of the charged system controlling sodium conductance in the squid giant axon , 1974, The Journal of physiology.

[16]  F. Conti,et al.  Structural parts involved in activation and inactivation of the sodium channel , 1989, Nature.

[17]  R. Greenblatt,et al.  The structure of the voltage‐sensitive sodium channel , 1985, FEBS letters.

[18]  E. Kosower,et al.  A structural and dynamic molecular model for the sodium channel of Electrophorus electricus , 1985, FEBS letters.

[19]  R. North,et al.  Cooperative interactions among subunits of a voltage-dependent potassium channel. Evidence from expression of concatenated cDNAs. , 1992, The Journal of biological chemistry.

[20]  M. Tanouye,et al.  Multiple products of the drosophila Shaker gene may contribute to potassium channel diversity , 1988, Neuron.

[21]  G. A. Lopez,et al.  Hydrophobic substitution mutations in the S4 sequence alter voltage-dependent gating in shaker K+ channels , 1991, Neuron.

[22]  F Bezanilla,et al.  Gating current noise produced by elementary transitions in Shaker potassium channels. , 1994, Science.

[23]  Jan Tytgat,et al.  Evidence for cooperative interactions in potassium channel gating , 1992, Nature.

[24]  K. Lindpaintner,et al.  Gating charge differences between two voltagegated K+ channels are due to the specific charge content of their respective S4 regions , 1993, Neuron.

[25]  F. Bezanilla,et al.  Currents Related to Movement of the Gating Particles of the Sodium Channels , 1973, Nature.

[26]  E. Isacoff,et al.  Direct Physical Measure of Conformational Rearrangement Underlying Potassium Channel Gating , 1996, Science.

[27]  W. Almers,et al.  Gating currents and charge movements in excitable membranes. , 1978, Reviews of physiology, biochemistry and pharmacology.

[28]  Y. Jan,et al.  Images of purified Shaker potassium channels , 1994, Current Biology.

[29]  Ehud Y. Isacoff,et al.  Transmembrane Movement of the Shaker K+ Channel S4 , 1996, Neuron.

[30]  W. Chandler,et al.  Voltage Dependent Charge Movement in Skeletal Muscle: a Possible Step in Excitation–Contraction Coupling , 1973, Nature.

[31]  F Bezanilla,et al.  Molecular basis of gating charge immobilization in Shaker potassium channels. , 1991, Science.

[32]  F J Sigworth,et al.  Voltage gating of ion channels , 1994, Quarterly Reviews of Biophysics.

[33]  S. Hausdorff,et al.  Design, synthesis, and functional expression of a gene for charybdotoxin, a peptide blocker of K+ channels. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[34]  A. Finkelstein,et al.  Identification of a translocated protein segment in a voltage-dependent channel , 1994, Nature.

[35]  Francisco Bezanilla,et al.  Charge Movement Associated with the Opening and Closing of the Activation Gates of the Na Channels , 1974, The Journal of general physiology.

[36]  T Hoshi,et al.  Shaker potassium channel gating. II: Transitions in the activation pathway , 1994, The Journal of general physiology.

[37]  M. Tanouye,et al.  The size of gating charge in wild-type and mutant Shaker potassium channels. , 1992, Science.

[38]  K. Lindpaintner,et al.  Incremental reductions of positive charge within the S4 region of a voltage-gated K+ channel result in corresponding decreases in gating charge , 1992, Neuron.

[39]  Yuichi Kanaoka,et al.  Primary structure of Electrophorus electricus sodium channel deduced from cDNA sequence , 1984, Nature.

[40]  R. MacKinnon.  Determination of the subunit stoichiometry of a voltage-activated potassium channel , 1991, Nature.