Shaker

About: Shaker is a research topic. Over the lifetime, 2178 publications have been published within this topic receiving 31219 citations.

Crystal Structure of a Mammalian Voltage-Dependent Shaker Family K + Channel

Abstract: Voltage-dependent potassium ion (K+) channels (Kv channels) conduct K+ ions across the cell membrane in response to changes in the membrane voltage, thereby regulating neuronal excitability by modulating the shape and frequency of action potentials. Here we report the crystal structure, at a resolution of 2.9 angstroms, of a mammalian Kv channel, Kv1.2, which is a member of the Shaker K+ channel family. This structure is in complex with an oxido-reductase beta subunit of the kind that can regulate mammalian Kv channels in their native cell environment. The activation gate of the pore is open. Large side portals communicate between the pore and the cytoplasm. Electrostatic properties of the side portals and positions of the T1 domain and beta subunit are consistent with electrophysiological studies of inactivation gating and with the possibility of K+ channel regulation by the beta subunit.

Biophysical and molecular mechanisms of shaker potassium channel inactivation

Abstract: The potassium channels encoded by the Drosophila Shaker gene activate and inactivate rapidly when the membrane potential becomes more positive. Site-directed mutagenesis and single-channel patch-clamp recording were used to explore the molecular transitions that underlie inactivation in Shaker potassium channels expressed in Xenopus oocytes. A region near the amino terminus with an important role in inactivation has now been identified. The results suggest a model where this region forms a cytoplasmic domain that interacts with the open channel to cause inactivation.

Cloning of genomic and complementary DNA from Shaker, a putative potassium channel gene from Drosophila.

Abstract: On the basis of electrophysiological analysis of Shaker mutants, the Shaker locus of Drosophila melanogaster has been proposed to encode a structural component of a voltage-dependent potassium channel, the A channel. Unlike sodium channels, acetylcholine receptors, and calcium channels, K+ channels have not been purified biochemically. To facilitate biochemical studies of a K+ channel, genomic DNA from the Shaker locus has been cloned. Rearrangements in five Shaker mutants have been mapped to a 60-kilobase segment of the genome. Four complementary DNA clones have been analyzed. These clones indicate that the Shaker gene contains multiple exons distributed over at least 65 kilobases of genomic DNA in the region where the mutations mapped. Furthermore, the gene may produce several classes of alternatively spliced transcripts. Two of the complementary DNA clones have been sequenced and their sequences support the hypothesis that Shaker encodes a component of a K+ channel.

Contribution of the S4 segment to gating charge in the Shaker K+ channel.

Abstract: 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 (∼4 electron charge units each) in the gating charge; however, the gating charge of Shaker Δ10, 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 NH 2 -terminal half but not the CO 2 H-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.

Voltage-Sensing Residues in the S2 and S4 Segments of the Shaker K+ Channel

Abstract: The activation of Shaker K + channels is steeply voltage dependent. To determine whether conserved charged amino acids in putative transmembrane segments S2, S3, and S4 contribute to the gating charge of the channel, the total gating charge movement per channel was measured in channels containing neutralization mutations. Of eight residues tested, four contributed significantly to the gating charge: E293, an acidic residue in S2, and R365, R368, and R371, three basic residues in the S4 segment. The results indicate that these residues are a major component of the voltage sensor. Furthermore, the S4 segment is not solely resposible for gating charge movement in Shaker K + channels.