ATPase activity of the sulfonylurea receptor:: a catalytic function for the KATP channel complex
ATPase activity of the sulfonylurea receptor:: a catalytic function for the KATP channel complex
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DOI：
10.1096/fj.00-0027com
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发表时间：
2000-10-01
期刊：
影响因子：
4.8
通讯作者：
Terzic, A
中科院分区：
文献类型：
--
作者：
Bienengraeber, M;Alekseev, AE;Terzic, A
ATP敏感的K+ (K-ATP)通道是一种独特的代谢传感器，由Kir6.2（一种向内纠偏的K+通道）和磺酰脲受体SUR（一种ATP结合盒蛋白）联合形成。我们在心脏K-ATP通道的免疫沉淀物和含有心脏SUR2A亚型核苷酸结合域NBD1和NBD2的纯化融合蛋白中发现了atp酶的活性。NBD2水解ATP的速率比NBD1高两倍，ATP酶需要Mg2+，对瓦巴因、寡霉素、萨普格尔素或左旋咪唑不敏感，NBD2的K1348A和D1469N突变降低了ATP酶的活性，并产生了对ATP敏感性增加的通道。与SUR结合的K-ATP通道打开剂促进了纯化的肌膜中atp酶的活性。在较高浓度下，打开剂降低了atp酶活性，可能是通过通道部位MgADP的稳定，K1348A和D1469N突变减弱了打开剂对K-ATP通道活性的影响。打开器诱导的通道激活也被肌酸激酶/磷酸肌酸系统抑制，该系统从通道复合体中去除ADP，因此，K- atp通道复合体不仅作为K+传导，而且作为一种酶，通过SUR亚基的内在atp酶活性调节核苷酸依赖性通道门控。通道atp酶活性的调节和/或清除atp酶反应的产物为调节与K-ATP通道打开相关的细胞功能提供了新的手段。
ATP-sensitive K+ (K-ATP) channels are unique metabolic sensors formed by association of Kir6.2, an inwardly rectifying K+ channel, and the sulfonylurea receptor SUR, an ATP binding cassette protein. We identified an ATPase activity in immunoprecipitates of cardiac K-ATP channels and in purified fusion proteins containing nucleotide binding domains NBD1 and NBD2 of the cardiac SUR2A isoform. NBD2 hydrolyzed ATP with a twofold higher rate compared to NBD1, The ATPase required Mg2+ and was insensitive to ouabain, oligomycin, thapsigargin, or levamisole, K1348A and D1469N mutations in NBD2 reduced ATPase activity and produced channels with increased sensitivity to ATP. K-ATP channel openers, which bind to SUR, promoted ATPase activity in purified sarcolemma. At higher concentrations, openers reduced ATPase activity, possibly through stabilization of MgADP at the channel site, K1348A and D1469N mutations attenuated the effect of openers on K-ATP channel activity. Opener-induced channel activation was also inhibited by the creatine kinase/creatine phosphate system that removes ADP from the channel complex, Thus, the K-ATP channel complex functions not only as a K+ conductance, but also as an enzyme regulating nucleotide-dependent channel gating through an intrinsic ATPase activity of the SUR subuniT. Modulation of the channel ATPase activity and/or scavenging the product of the ATPase reaction provide novel means to regulate cellular functions associated with K-ATP channel opening.