PT  - JOURNAL ARTICLE
AU  - Gross, Insa
AU  - Toman, Andreas
AU  - Uhde, Ingo
AU  - Schwanstecher, Christina
AU  - Schwanstecher, Mathias
TI  - Stoichiometry of Potassium Channel Opener Action
AID  - 10.1124/mol.56.6.1370
DP  - 1999 Dec 01
TA  - Molecular Pharmacology
PG  - 1370--1373
VI  - 56
IP  - 6
4099  - http://molpharm.aspetjournals.org/content/56/6/1370.short
4100  - http://molpharm.aspetjournals.org/content/56/6/1370.full
SO  - Mol Pharmacol1999 Dec 01; 56
AB  - Potassium channel openers (KCOs; e.g., P1075, pinacidil) exert their effects on excitable cells by opening ATP-sensitive potassium channels. These channels are heteromultimers composed with a 4:4 stoichiometry of an inwardly rectifying K+ channel subunit plus a regulatory subunit comprising the receptor sites for hypoglycemic sulfonylureas and KCOs (a sulfonylurea receptor). To elucidate stoichiometry of KCO action, we analyzed P1075 sensitivity of channels coassembled from sulfonylurea receptor isoforms with high or low P1075 affinity. Concentration activation curves for cDNA ratios of 1:1 or 1:10 resembled those for channel opening resulting from interaction with a single site, whereas models for activation requiring occupation of two, three, or four sites were incongruous. We conclude KCO-induced channel activation to be mediated by interaction with a single binding site per tetradimeric complex.