Subunit stoichiometry of the pancreatic β‐cell ATP‐sensitive K+ channel

FEBS Letters

Seino, Susumu¹  Gonoi, Tohru²  Inagaki, Nobuya¹ 

[1] Division of Molecular Medicine, Center for Biomedical Science, Chiba University School of Medicine, Chuo-ku, Chiba 260, Japan;Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Chuo-ku, Chiba 260, Japan

关键词: Potassium channel;    ATP;    Inward rectifier;    Sulfonylurea receptor;    Stoichiometry;   

DOI  :  10.1016/S0014-5793(97)00488-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

We have investigated the subunit stoichiometry of the pancreatic β-cell ATP-sensitive K⁺ (K_ATP) channel (SUR1/Kir6.2 channel) by constructing cDNA encoding a single polypeptide (βα polypeptide) consisting of a SUR1 (β) subunit and a Kir6.2 (α) subunit. ⁸⁶Rb⁺ efflux and single-channel properties of COS1 cells expressing βα polypeptides were similar to those of COS1 cells coexpressing α monomers and β monomers. Coexpression of βα polypeptides with α monomers inhibited the K⁺ currents, while coexpression with β monomers did not. We then constructed another single polypeptide (βα₂) consisting of a β subunit and a dimeric repeat of the α subunit. ⁸⁶Rb⁺ efflux from COS1 cells expressing βα₂ polypeptides was small, but was restored by supplementation with β monomers. These results indicate that the activity of K_ATP channels is optimized when the α and β subunits are coexpressed with a molar ratio of 1:1. Since inward rectifier K⁺ channels are thought to function as homo- or hetero-tetramers, this suggests that the K_ATP channel functions as a multimeric protein, most likely a hetero-octamer composed of a tetramer of the Kir6.2 subunit and a tetramer of the SUR1 subunit.

【 授权许可】

Unknown