The tolbutamide site of SUR1 and a mechanism for its functional coupling to KATP channel closure

FEBS Letters

Bryan, Joseph¹  Babenko, Andrey P¹  Gonzalez, Gabriela¹ 

[1] Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA

关键词: ATP-sensitive potassium inward rectifier;    Gating;    ATP-binding cassette;    Transport ATPase;    SUR2A;    KIR6.0;   

DOI  :  10.1016/S0014-5793(99)01215-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Micromolar concentrations of tolbutamide will inhibit (SUR1/K_IR6.2)₄ channels in pancreatic β-cells, but not (SUR2A/K_IR6.2)₄ channels in cardiomyocytes. Inhibition does not require Mg²⁺ or nucleotides and is enhanced by intracellular nucleotides. Using chimeras between SUR1 and SUR2A, we show that transmembrane domains 12–17 (TMD12-17) are required for high-affinity tolbutamide inhibition of K_ATP channels. Deletions demonstrate involvement of the cytoplasmic N-terminus of K_IR6.2 in coupling sulfonylurea-binding with SUR1 to the stabilization of an interburst closed configuration of the channel. The increased efficacy of tolbutamide by nucleotides results from an impairment of their stimulatory action on SUR1 which unmasks their inhibitory effects. The mechanism of inhibition of β-cell K_ATP channels by sulfonylureas during treatment of non-insulin-dependent diabetes mellitus thus involves two components, drug-binding and conformational changes within SUR1 which are coupled to the pore subunit through its N-terminus and the disruption of nucleotide-dependent stimulatory effects of the regulatory subunit on the pore. These findings uncover a molecular basis for an inhibitory influence of SUR1, an ATP-binding cassette (ABC) protein, on K_IR6.2, a ion channel subunit.

【 授权许可】

Unknown