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Volume-regulated anion channels are activated in response to hypotonic stress. These channels are composed of closely related paralogues of the leucine-rich repeat-containing protein 8 (LRRC8) family that co-assemble to form hexameric complexes. Here, using cryo-electron microscopy and X-ray crystallography, we determine the structure of a homomeric channel of the obligatory subunit LRRC8A. This protein conducts ions and has properties in common with endogenous heteromeric channels. Its modular structure consists of a transmembrane pore domain followed by a cytoplasmic leucine-rich repeat domain. The transmembrane domain, which is structurally related to connexin proteins, is wide towards the cytoplasm but constricted on the outside by a structural unit that acts as a selectivity filter. An excess of basic residues in the filter and throughout the pore attracts anions by electrostatic interaction. Our work reveals the previously unknown architecture of volume-regulated anion channels and their mechanism of selective anion conduction.The structure of a homomeric channel of subunit A of leucine-rich repeat-containing protein 8 (LRRC8) determined by cryo-electron microscopy and X-ray crystallography reveals the basis for anion selectivity., Author(s): Dawid Deneka [sup.1] , Marta Sawicka [sup.1] , Andy K. M. Lam [sup.1] , Cristina Paulino [sup.1] [sup.2] , Raimund Dutzler [sup.1] Author Affiliations:(1) Department of Biochemistry, University of [...]