The S4 voltage sensor packs against the pore domain in the KAT1 voltage-gated potassium channel.
In voltage-gated ion channels, the S4 transmembrane segment responds to changes in membrane potential and controls channel opening. The local environment of S4 is still unknown, even regarding the basic question as to whether S4 is close to the pore domain. Relying on the ability of functional KAT1 channels to rescue potassium (K+) transport-deficient yeast, we have performed an unbiased mutagenesis screen aimed at determining whether S4 packs against S5 of the pore domain. Starting with semilethal mutations of surface-exposed S5 residues of the KAT1 pore domain, we have screened randomly mutagenized libraries of S4 or S1-S3 for second-site suppressors. Our study identifies two S4 residues that interact in a highly specific manner with two S5 residues in the middle of the membrane-spanning regions, supporting a model in which the S4 voltage sensor packs against the pore domain in the hyperpolarized, or "down," state of S4.
Lai
Helen C
HC
Graduate Group in Biophysics, University of California, San Francisco, San Francisco, California 94143, USA.
Grabe
Michael
M
Jan
Yuh Nung
YN
Jan
Lily Yeh
LY
D000818:Animals; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D004594:Electrophysiology; D005804:Genes, Lethal; D008958:Models, Molecular; D009154:Mutation; D009865:Oocytes; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D014981:Xenopus; D015003:Yeasts
D029681:Arabidopsis Proteins; C501210:KAT1 protein, Arabidopsis; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated