A minK–HERG complex regulates the cardiac potassium current IKr

MinK is a widely expressed protein of relative molecular mass ∼15K that forms potassium channels by aggregation with other membrane proteins1,2,3. MinK governs ion channel activation4, regulation by second messengers5,6, and the function and structure of the ion conduction pathway7,8. Association of minK with a channel protein known as KvLQT1 produces a voltage-gated outward K+ current (IsK) resembling the slow cardiac repolarization current (IKs)9,10. HERG, a human homologue of the ether-a-go-go gene of the fruitfly Drosophila melanogaster, encodes a protein that produces the rapidly activating cardiac delayed rectifier (IKr)11,12. These two potassium currents, IKs and IKr, provide the principal repolarizing currents in cardiac myocytes for the termination of action potentials13,14. Although heterologously expressed HERG channels are largely indistinguishable from native cardiac IKr, a role for minK in this current is suggested by the diminished IKr in an atrial tumour line subjected to minK antisense suppression15. Here we show that HERG and minK form a stable complex, and that this heteromultimerization regulates IKr activity. MinK, through the formation of heteromeric channel complexes, is thus central to the control of the heart rate and rhythm.