Specific interaction of the potassium channel β-subunit minK with the sarcomeric protein T-cap suggests a T-tubule-myofibril linking system

Ion-channel β-subunits are ancillary proteins that co-assemble with α-subunits to modulate gating kinetics and enhance stability of multimeric channel complexes. They provide binding sites for other regulatory proteins and are medically important as the targets of many pharmacological compounds. MinK is the β-subunit of the slow activating component of the delayed rectifier potassium current (IKs) channel, and associates with the α-subunit, KvLQT1. We report here that minK specifically interacts with the sarcomeric Z-line component, T-cap (also called telethonin). In vitro interaction studies indicated that the cytoplasmic domain of minK specifically binds to the sixteen C-terminal residues of T-cap; these residues are sufficient for its interaction with minK.