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Subunit stoichiometry of the pancreatic β‐cell ATP‐sensitive K + channel
Author(s) -
Inagaki Nobuya,
Gonoi Tohru,
Seino Susumu
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)00488-2
Subject(s) - tetramer , protein subunit , g alpha subunit , beta (programming language) , scn3a , chemistry , biophysics , potassium channel , microbiology and biotechnology , biology , biochemistry , enzyme , gene , computer science , programming language
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. 86 Rb + 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 (βα 2 ) consisting of a β subunit and a dimeric repeat of the α subunit. 86 Rb + efflux from COS1 cells expressing βα 2 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.