The ATP-sensitive potassium (KATP) channel formed by four Kir6.2 and four SUR1 subunits regulate insulin secretion in ?-cells by coupling glucose metabolism with membrane excitability. Mutations in the ?-cell KATP channel causes abnormal insulin secretion and loss of blood glucose control. Our long-term goal is to understand the structure-function relationships of KATP channels in order to develop mechanistic therapies for diseases caused by KATP channel dysfunction. We have been successful in obtaining cryoEM structures of the channel bound to inhibitors in closed conformations. In this proposal we aim to obtain structures of the channel in its open conformations by reconstituting purified channels into nanodiscs containing activating lipids, determining channel structures in the presence of channel openers, and employing channels harboring mutations known to cause constitutive channel opening. The study will advance our understanding of the structural changes associated with channel gating and facilitate structure-based drug design for disease therapy.