Structure of a Pancreatic ATP-Sensitive Potassium Channel.

Abstract

ATP-sensitive potassium channels (K_ATP) couple intracellular ATP levels with membrane excitability. These channels play crucial roles in many essential physiological processes and have been implicated extensively in a spectrum of metabolic diseases and disorders. To gain insight into the mechanism of K_ATP, we elucidated the structure of a hetero-octameric pancreatic K_ATP channel in complex with a non-competitive inhibitor glibenclamide by single-particle cryoelectron microscopy to 5.6-Å resolution. The structure shows that four SUR1 regulatory subunits locate peripherally and dock onto the central Kir6.2 channel tetramer through the SUR1 TMD0-L0 fragment. Glibenclamide-bound SUR1 uses TMD0-L0 fragment to stabilize Kir6.2 channel in a closed conformation. In another structural population, a putative co-purified phosphatidylinositol 4,5-bisphosphate (PIP₂) molecule uncouples Kir6.2 from glibenclamide-bound SUR1. These structural observations suggest a molecular mechanism for K_ATP regulation by anti-diabetic sulfonylurea drugs, intracellular adenosine nucleotide concentrations, and PIP₂ lipid.