Role of the amino-terminal transmembrane domain of sulfonylurea receptor SUR2B for coupling to K(IR)6.2, ligand binding, and oligomerization.
Role of the amino-terminal transmembrane domain of sulfonylurea receptor SUR2B for coupling to K(IR)6.2, ligand binding, and oligomerization.
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磺酰脲类受体 SUR2B 的氨基末端跨膜结构域在与 K(IR)6.2 偶联、配体结合和寡聚化中的作用。
DOI：
10.1007/s00210-011-0708-9
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Quast,Ulrich
中科院分区：
文献类型：
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作者：
Winkler,Marcus;Kühner,Petra;Russ,Ulrich;Ortiz,David;Bryan,Joseph;Quast,Ulrich
ATP敏感K+(KATP)通道由两种亚基组成，KIR6.x和磺脲受体(SURS)，KIR6.x形成孔道，SURS作为调节亚单位。SURS是一种三磷酸腺苷结合盒(ABC)蛋白，除了两个核苷酸结合折叠外，还含有通道开放剂(如二氮卓和P1075)以及通道抑制剂(如格列本脲和瑞格列奈)的结合部位。在结构上，SURS与大多数真核ABC蛋白的不同之处在于有一个额外的氨基末端跨膜结构域(TMD0)；对于胰腺KATP通道的亚单位SUR1，TMD0是与KIR相关的主要结构域。在这项研究中，我们试图阐明TMD0在SUR2B中的作用，SUR2B是SUR2B的门控亚基，在SUR2B和KIR6.2之间的偶联中，TMD0在SUR2B的自结合和通道调节剂与SUR2B的结合中发挥作用。SUR2B对磺脲类的亲和力较弱，因此SUR2BY1206S对GBC的亲和力较高，但使用了等效的开放剂结合。免疫沉淀显示缺失TMD0的SUR2BYSΔ与KIR6.2结合；然而，没有证据表明有功能通道的形成。与SUR2BYS类似的SUR2BYSΔ自我结合结合GBC、瑞格列奈和P1075的亲和力略有降低。SUR2BYSΔ/KIR6.2复合体的结合谱与单独的SUR2BYSΔ的结合谱略有不同，但有显著差异，表明结合位点的变构偶联作用减弱。我们的结论是，TMD0不是SUR2B齐聚所必需的，在配体结合中只是次要的，但对于SUR2B与KIR6.2的功能性和变构偶联都是必不可少的。
ATP-sensitive K+(KATP) channels consist of two types of subunits, KIR6.x that form the pore, and sulfonylurea receptors (SURs) that serve as regulatory subunits. SURs are ATP-binding cassette (ABC) proteins and contain, in addition to two nucleotide binding folds, the binding sites for channel openers such as diazoxide and P1075 and channel inhibitors such as glibenclamide (GBC) and repaglinide. Structurally, SURs differ from most eukaryotic ABC proteins by an additional amino-terminal transmembrane domain (TMD0); in case of SUR1, the subunit of the pancreatic KATPchannel, TMD0 serves as a major domain for association with KIR. In this study we sought to elucidate the roles of TMD0 in SUR2B, the smooth muscle gating subunit, in the coupling between SUR2B and KIR6.2, in the self-association of SUR2B and in channel modulator binding to SUR2B. SUR2B has a weaker affinity for sulfonylureas thus SUR2BY1206S, with a higher affinity for GBC, but an equivalent opener binding was used. Association of SUR2BYSΔ, lacking TMD0, with KIR6.2 was shown by immunoprecipitation; however, no evidence for formation of functional channels was obtained. SUR2BYSΔ self-associates like SUR2BYSand binds GBC, repaglinide, and P1075 with slightly reduced affinities. The binding profile of the SUR2BYSΔ/KIR6.2 complex differs slightly but significantly from that of SUR2BYSΔ alone showing impaired allosteric coupling of binding sites. We conclude that TMD0 is not required for oligomerization of SUR2B, is of only minor importance in ligand binding, but is essential for both functional and allosteric coupling of SUR2B to KIR6.2.