Schwanstecher M, Sieverding C, Dörschner H, Gross I, Aguilar-Bryan L, Schwanstecher C, Bryan J
Institut für Pharmakologie und Toxikologie, Universität Braunschweig, Mendelssohnstrasse 1, 38106 Braunschweig, Germany.
EMBO J. 1998 Oct 1;17(19):5529-35. doi: 10.1093/emboj/17.19.5529.
KATP channels are composed of a small inwardly rectifying K+ channel subunit, either KIR6.1 or KIR6.2, plus a sulfonylurea receptor, SUR1 or SUR2 (A or B), which belong to the ATP-binding cassette superfamily. SUR1/KIR6.2 reconstitute the neuronal/pancreatic beta-cell channel, whereas SUR2A/KIR6.2 and SUR2B/KIR6.1 (or KIR6.2) are proposed to reconstitute the cardiac and the vascular-smooth-muscle-type KATP channels, respectively. We report that potassium channel openers (KCOs) bind to and act through SURs and that binding to SUR1, SUR2A and SUR2B requires ATP. Non-hydrolysable ATP-analogues do not support binding, and Mg2+ or Mn2+ are required. Point mutations in the Walker A motifs or linker regions of both nucleotide-binding folds (NBFs) abolish or weaken [3H]P1075 binding to SUR2B, rendering reconstituted SUR2B/KIR6.2 channels insensitive towards KCOs. The C-terminus of SUR affects KCO affinity with SUR2B approximately SUR1 > SUR2A. KCOs belonging to different structural classes inhibited specific [3H]P1075 binding to SUR2B in a monophasic manner, with the exception of minoxidil sulfate, which induced a biphasic displacement. The affinities of KCO binding to SUR2B were 3.5-8-fold higher than their potencies for activation of SUR2B/KIR6.2 channels. The results establish that SURs are the KCO receptors of KATP channels and suggest that KCO binding requires a conformational change induced by ATP hydrolysis in both NBFs.
KATP通道由一个内向整流性小K⁺通道亚基（KIR6.1或KIR6.2）和一个磺脲类受体（SUR1或SUR2（A或B））组成，后者属于ATP结合盒超家族。SUR1/KIR6.2重构神经元/胰腺β细胞通道，而SUR2A/KIR6.2和SUR2B/KIR6.1（或KIR6.2）分别被认为重构心脏和血管平滑肌型KATP通道。我们报道钾通道开放剂（KCOs）通过SURs结合并发挥作用，且与SUR1、SUR2A和SUR2B的结合需要ATP。不可水解的ATP类似物不支持结合，且需要Mg²⁺或Mn²⁺。两个核苷酸结合结构域（NBFs）的沃克A基序或连接区的点突变消除或减弱[³H]P1075与SUR2B的结合，使重构的SUR2B/KIR6.2通道对KCOs不敏感。SUR的C末端对KCO与SUR2B的亲和力影响约为SUR1 > SUR2A > SUR2B。除硫酸米诺地尔诱导双相置换外，不同结构类别的KCOs以单相方式抑制[³H]P1075与SUR2B的特异性结合。KCO与SUR2B结合的亲和力比它们激活SUR2B/KIR6.2通道的效力高3.5 - 8倍。结果表明SURs是KATP通道的KCO受体，并提示KCO结合需要由两个NBFs中ATP水解诱导的构象变化。
