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Soluble guanylate cyclase (sGC) is the primary sensor of nitric oxide. It has a central role in nitric oxide signalling and has been implicated in many essential physiological processes and disease conditions. The binding of nitric oxide boosts the enzymatic activity of sGC. However, the mechanism by which nitric oxide activates the enzyme is unclear. Here we report the cryo-electron microscopy structures of the human sGC[alpha]1[beta]1 heterodimer in different functional states. These structures revealed that the transducer module bridges the nitric oxide sensor module and the catalytic module. Binding of nitric oxide to the [beta]1 haem-nitric oxide and oxygen binding (H-NOX) domain triggers the structural rearrangement of the sensor module and a conformational switch of the transducer module from bending to straightening. The resulting movement of the N termini of the catalytic domains drives structural changes within the catalytic module, which in turn boost the enzymatic activity of sGC. Cryo-electron microscopy structures of human soluble guanylate cyclase in inactive and activated states shed light on the activation mechanism of this enzyme by nitric oxide., Author(s): Yunlu Kang [sup.1] , Rui Liu [sup.1] , Jing-Xiang Wu [sup.1] , Lei Chen [sup.1] [sup.2] [sup.3] Author Affiliations: (1) State Key Laboratory of Membrane Biology, Institute of Molecular [...]

Repaglinide (RPG) is a short-acting insulin secretagogue widely prescribed for the treatment of type 2 diabetes. It boosts insulin secretion by inhibiting the pancreatic ATP-sensitive potassium channel (K ATP ). However, the mechanisms by which RPG binds to the K ATP channel are poorly understood. Here, we describe two cryo-EM structures: the pancreatic K ATP channel in complex with inhibitory RPG and adenosine-5'-(γ-thio)-triphosphate (ATPγS) at 3.3 Å and a medium-resolution structure of a RPG-bound mini SUR1 protein in which the N terminus of the inward-rectifying potassium channel 6.1 (Kir6.1) is fused to the ABC transporter module of the sulfonylurea receptor 1 (SUR1). These structures reveal the binding site of RPG in the SUR1 subunit. Furthermore, the high-resolution structure reveals the complex architecture of the ATP binding site, which is formed by both Kir6.2 and SUR1 subunits, and the domain-domain interaction interfaces., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)