Nakajo K , Kubo Y .

	Figure 1. Cysteine-scanning mutagenesis of the S4 segment of the KCNQ1 channel. (A) Amino acid sequences of the S3–S4 linker and S4 segment of human KCNQ1 (hKCNQ1), Drosophila Shaker (Shaker), and human Kv1.2 (hKv1.2) are aligned. Amino acids substituted with cysteine are shaded in gray. Endogenous cysteine (C214; yellow) was substituted with alanine in all mutants. Positively and negatively charged amino acids are indicated in red and blue, respectively. (B) Representative traces for C214A and A226C in the absence and presence of KCNE1. Membrane potential was depolarized for 2 s from −80 to +40 mV in 10-mV steps in the absence of KCNE1 and from −80 to +60 mV in 20-mV steps in the presence of KCNE1. (C) Conductance–voltage (G-V) relationships for C214A (black) and A226C (red) with (open symbols) and without (filled symbols) KCNE1 are shown. Data are fitted with Boltzmann equation (dotted curves, see Materials and Methods).
	Figure 2. Reaction with MTS reagents locks A226C mutant open. (A) Representative traces for C214A and A226C obtained in the presence of KCNE1 (E1) after a 30-min pretreatment with 1 mM MTSET. A226C was stabilized in the open state after MTSET treatment. Membrane potential was stepped from −120 to +40 mV in 20-mV increments. Holding potential was −90 mV. (B) G-V curves with (red) and without (black) MTSET pretreatment in the presence of KCNE1. (C) Representative traces for C214A and A226C obtained in the absence of KCNE1 after a 30-min pretreatment with 1 mM MTSET. Membrane potential was stepped from −100 to +60 mV in 20-mV increments. Holding potential was −80 mV. (D) G-V curves with (red) and without (black) MTSET pretreatment in the absence of KCNE1.
	Figure 3. MTS reaction rate is slowed in the KCNQ1–KCNE1 complex. (A) Pulse protocols for MTSES application. Depolarizing pulses (to +40 mV) with durations of 30 ms (blue), 300 ms (red), or 3 s (black) were applied every 10 s. (B) Representative traces for A226C (30 ms), A226C (300 ms), A226C+KCNE1 (300 ms), and A226C+E1 (3 s). Traces obtained just before applying MTSES are shown in red; those obtained 1, 2, 3, 4, and 5 min after the onset of MTSES application are shown in black. (C) Time courses of the MTSES reaction with A226C and A226C+KCNE1 with 30-ms (blue), 300-ms (red), and 3-s (black) depolarizing pulses. The timing of the MTSES application is indicated by black bars. (D) Time courses of MTSES reaction are replotted as functions of “exposure (mM sec)” (see Materials and Methods) of A226C+KCNE1 elicited by 30-ms (blue), 300-ms (red), and 3-s (black) depolarizing pulses. (E) Time courses of the MTSES reaction with 300-ms pulses in terms of “exposure” are compared between A226C and A226C+KCNE1 (E1). Filled red symbols represent A226C, open black symbols A226C+KCNE1. (F) Apparent second order rate constants are plotted. Although time courses of MTSES reaction with A226C (300 ms) and A226C+KCNE1 (3 s) were fitted by a double exponential function, only the faster time constants were used for calculation of the apparent second order rate constants. Filled bars represent rate constants without KCNE1, open bars the rate constants with KCNE1; **, P < 0.01.
	Figure 4. MTS reaction rate is voltage dependent. (A) Time courses of MTSES reaction with A226C (300 ms) and A226C+KCNE1 (3 s) with depolarization to −40, 0, +40, and +80 mV are shown. (B) Apparent second order rate constants are plotted against voltage. Although time courses of the reaction with depolarizations to +40 and +80 mV were fitted with double exponential function, only the faster time constants were used for the calculation of the apparent second order rate constants. Filled bars represent rate constants without KCNE1, open bars the rate constants with KCNE1.
	Figure 5. The rate of MTS reaction with the KCNQ1–KCNE3 complex is voltage independent. (A) Representative traces obtained from oocyte coexpressing KCNQ1 (A226C) and KCNE3 (C31A) before and 5 min after application of 1 mM MTSES. Membrane potential was stepped from a holding potential of −100 to +60 mV in 20-mV increments. (B) G-V relationships for A226C+KCNE3 before (black) and after (red) MTSES application. (C) Representative traces obtained with 30-ms depolarizations to +40 mV or 300-ms depolarizations to +40 or −40 mV in oocytes expressing A226C+KCNE3. Traces just before applying MTSES are shown in red; those recorded 1, 2, and 3 min after the onset of MTSES application are shown in black. (D) Time courses of the MTSES reaction with A226C+KCNE3. Error bars were omitted for clarity. The timing of MTSES application is indicated by a black bar. (E) Two second order rate constants (kfast and kslow) are plotted for each protocol. They are calculated from two time constants obtained from D fitted using a double exponential function.
	Figure 6. A disulfide bond can form between KCNE1 and S4 of KCNQ1. (A) Current traces recorded from an oocyte coexpressing KCNQ1 (A226C) and KCNE1 (E44C) are shown. The oocyte was repetitively depolarized to +40 mV for 3 s every 10 s. Only the 1st, 12th, and 13th traces are shown. The current gradually ran down until by the 12th depolarization it was nearly flat. With subsequent addition of 1 mM DTT, the current immediately recovered the slow activation (13th depolarization). Thereafter, slow activation was retained in DTT. (inset) Time course of the run down and recovery by DTT. Filled and open symbols represent the instantaneous currents and the currents at the end of the depolarization, respectively. Black bar represents the presence of 1 mM DTT in the bath solution. (B) Time course of current amplitude upon DTT application (n = 5). Filled and open symbols represent the instantaneous currents and the currents at the end of the depolarization, respectively. Black bar represents the presence of 1 mM DTT in bath solution. (C) Representative traces obtained from oocyte coexpressing KCNQ1 A226C mutant and KCNE1 E44C mutant. Membrane potential was stepped from a holding potential of −100 to +60 mV in 20-mV increments. After the first set of voltage pulses (left), oocyte is depolarized at +40 mV for 1 min to facilitate the disulfide formation. Second set of voltage pulses was applied after 1 min depolarization (right). (D) G-V curves for the KCNQ mutants with KCNE1 (E44C) mutant. Open and filled symbols represent G-V curves before and after 1 min depolarization at +40 mV, respectively.

Abbott, MiRP1 forms IKr potassium channels with HERG and is associated with cardiac arrhythmia. 1999, Pubmed, Xenbase

Abbott, MiRP1 forms IKr potassium channels with HERG and is associated with cardiac arrhythmia. 1999, Pubmed , Xenbase
Abbott, MiRP2 forms potassium channels in skeletal muscle with Kv3.4 and is associated with periodic paralysis. 2001, Pubmed , Xenbase
Akabas, Acetylcholine receptor channel structure probed in cysteine-substitution mutants. 1992, Pubmed , Xenbase
Barhanin, K(V)LQT1 and lsK (minK) proteins associate to form the I(Ks) cardiac potassium current. 1996, Pubmed , Xenbase
Bell, Changes in local S4 environment provide a voltage-sensing mechanism for mammalian hyperpolarization-activated HCN channels. 2004, Pubmed , Xenbase
Gage, KCNE3 truncation mutants reveal a bipartite modulation of KCNQ1 K+ channels. 2004, Pubmed , Xenbase
Gutman, International Union of Pharmacology. LIII. Nomenclature and molecular relationships of voltage-gated potassium channels. 2005, Pubmed
Isacoff, Evidence for the formation of heteromultimeric potassium channels in Xenopus oocytes. 1990, Pubmed , Xenbase
Kurokawa, TEA(+)-sensitive KCNQ1 constructs reveal pore-independent access to KCNE1 in assembled I(Ks) channels. 2001, Pubmed
Larsson, Transmembrane movement of the shaker K+ channel S4. 1996, Pubmed , Xenbase
Ledwell, Mutations in the S4 region isolate the final voltage-dependent cooperative step in potassium channel activation. 1999, Pubmed , Xenbase
Long, Crystal structure of a mammalian voltage-dependent Shaker family K+ channel. 2005, Pubmed
Mannuzzu, Direct physical measure of conformational rearrangement underlying potassium channel gating. 1996, Pubmed , Xenbase
Melman, A single transmembrane site in the KCNE-encoded proteins controls the specificity of KvLQT1 channel gating. 2002, Pubmed
Melman, Structural determinants of KvLQT1 control by the KCNE family of proteins. 2001, Pubmed
Melman, KCNE regulation of KvLQT1 channels: structure-function correlates. 2002, Pubmed
Melman, KCNE1 binds to the KCNQ1 pore to regulate potassium channel activity. 2004, Pubmed
Panaghie, The role of S4 charges in voltage-dependent and voltage-independent KCNQ1 potassium channel complexes. 2007, Pubmed , Xenbase
Panaghie, Interaction of KCNE subunits with the KCNQ1 K+ channel pore. 2006, Pubmed , Xenbase
Papazian, Cloning of genomic and complementary DNA from Shaker, a putative potassium channel gene from Drosophila. 1987, Pubmed
Rocheleau, Secondary structure of a KCNE cytoplasmic domain. 2006, Pubmed , Xenbase
Ruppersberg, Heteromultimeric channels formed by rat brain potassium-channel proteins. 1990, Pubmed , Xenbase
Sanguinetti, Coassembly of K(V)LQT1 and minK (IsK) proteins to form cardiac I(Ks) potassium channel. 1996, Pubmed , Xenbase
Schroeder, A constitutively open potassium channel formed by KCNQ1 and KCNE3. 2000, Pubmed , Xenbase
Schulze-Bahr, KCNE1 mutations cause jervell and Lange-Nielsen syndrome. 1997, Pubmed
Seebohm, Differential roles of S6 domain hinges in the gating of KCNQ potassium channels. 2006, Pubmed , Xenbase
Sesti, Single-channel characteristics of wild-type IKs channels and channels formed with two minK mutants that cause long QT syndrome. 1998, Pubmed , Xenbase
Smith-Maxwell, Role of the S4 in cooperativity of voltage-dependent potassium channel activation. 1998, Pubmed , Xenbase
Smith-Maxwell, Uncharged S4 residues and cooperativity in voltage-dependent potassium channel activation. 1998, Pubmed , Xenbase
Splawski, Mutations in the hminK gene cause long QT syndrome and suppress IKs function. 1997, Pubmed , Xenbase
Tai, The conduction pore of a cardiac potassium channel. 1998, Pubmed , Xenbase
Tai, MinK potassium channels are heteromultimeric complexes. 1997, Pubmed , Xenbase
Takumi, Cloning of a membrane protein that induces a slow voltage-gated potassium current. 1988, Pubmed , Xenbase
Takumi, Alteration of channel activities and gating by mutations of slow ISK potassium channel. 1991, Pubmed , Xenbase
Tapper, Location and orientation of minK within the I(Ks) potassium channel complex. 2001, Pubmed , Xenbase
Tapper, MinK subdomains that mediate modulation of and association with KvLQT1. 2000, Pubmed , Xenbase
Timpe, Expression of functional potassium channels from Shaker cDNA in Xenopus oocytes. 1988, Pubmed , Xenbase
Vemana, S4 movement in a mammalian HCN channel. 2004, Pubmed , Xenbase
Wang, Positional cloning of a novel potassium channel gene: KVLQT1 mutations cause cardiac arrhythmias. 1996, Pubmed
Wang, KCNQ2 and KCNQ3 potassium channel subunits: molecular correlates of the M-channel. 1998, Pubmed , Xenbase
Wang, MinK residues line a potassium channel pore. 1996, Pubmed
Yang, Single-channel properties of IKs potassium channels. 1998, Pubmed , Xenbase
Yang, Molecular basis of charge movement in voltage-gated sodium channels. 1996, Pubmed