Functional dissection of KATP channel structures reveals the importance of a conserved interface

ATP-sensitive potassium channels (KATP) are inhibited by ATP but activated by Mg-ADP, coupling the intracellular ATP/ADP ratio to the potassium conductance of the plasma membrane. Although there has been progress in determining the structure of KATP channels, the functional significance of the domain-domain interface in the gating properties of KATP channels is not fully understood. In this study, we propose a new two-module assembly model for the KATP channel. Our mutagenesis experiments, based on this model, indicate that deleting ECL3 on the SUR1 subunit impairs KNtp-independent Mg-ADP activation. This finding demonstrates the essential role of intramolecular interactions between KATP _core and SUR _ABC in Mg-ADP activation. Notably, this interface is functionally conserved between SUR1 and SUR2. Additionally, the hydrophobic residue F351 on ECL3 of SUR1 is crucial for maintaining the stability of this interface.