Regulation of K-ATP channel activity by diazoxide and MgADP - Distinct functions of the two nucleotide binding folds of the sulfonylurea receptor
Regulation of K-ATP channel activity by diazoxide and MgADP - Distinct functions of the two nucleotide binding folds of the sulfonylurea receptor
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DOI：
10.1085/jgp.110.6.643
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发表时间：
1997-12-01
影响因子：
3.8
通讯作者：
Nichols, CG
中科院分区：
文献类型：
--
作者：
Shyng, SL;Ferrigni, T;Nichols, CG
K-ATP通道在COSm 6细胞中通过共表达磺酰脲受体SUR 1和内向整流钾通道Kir6.2来重建。研究了SUR 1的两个核苷酸结合折叠在核苷酸和二氮嗪调节K-ATP通道活性中的作用。接头区和步行者B基序中的突变（步行者，J.E.，M.J. Saraste，M.J. Runswick，和N.J. Gay. 1952. EMBO [Eur.摩尔生物器官] J. 1：945-951），包括G1479 D、G1479 R、G1485 D、G1485 R、Q1486 H和D1506 A，都消除了MgADP和二氮嗪的刺激，除了G1479 R，其显示出对二氮嗪的小刺激应答。在第一个核苷酸结合折叠，包括G827 D，G827 R和Q834 H，类似的突变，仍然刺激二氮嗪和MgADP，但与野生型通道相比，改变动力学。这些突变都没有改变通道对ATP（4-）抑制的敏感性。我们提出了一个模型，在该模型中，SUR 1敏感的K-ATP通道ATP抑制，和核苷酸水解的核苷酸结合折叠块这种效果。MgADP和二氮嗪被提议用于稳定通道的这种脱敏状态，并且核苷酸结合折叠处的突变通过改变核苷酸水解速率或水解与通道活化的偶联来改变通道对MgADP和二氮嗪的响应。
K-ATP channels were reconstituted in COSm6 cells by coexpression of the sulfonylurea receptor SUR1 and the inward rectifier potassium channel Kir6.2. The role of the two nucleotide binding folds of SUR1 in regulation of K-ATP channel activity by nucleotides and diazoxide was investigated. Mutations in the linker region and the Walker B motif (Walker, J.E., M.J. Saraste, M.J. Runswick, and N.J. Gay. 1952. EMBO [Eur. Mol. Biol. Organ.] J. 1:945-951) of the second nucleotide binding fold, including G1479D, G1479R, G1485D, G1485R, Q1486H, and D1506A, all abolished stimulation by MgADP and diazoxide, with the exception of G1479R, which showed a small stimulatory response to diazoxide. Analogous mutations in the first nucleotide binding fold, including G827D, G827R, and Q834H, were still stimulated by diazoxide and MgADP, but with altered kinetics compared with the wild-type channel. None of the mutations altered the sensitivity of the channel to inhibition by ATP(4-). We propose a model in which SUR1 sensitizes the K-ATP channel to ATP inhibition, and nucleotide hydrolysis at the nucleotide binding folds blocks this effect. MgADP and diazoxide are proposed to stabilize this desensitized state of the channel, and mutations at the nucleotide binding folds alter the response of channels to MgADP and diazoxide by altering nucleotide hydrolysis rates or the coupling of hydrolysis to channel activation.