Referenced in: none

Automatically associated channels: ClC4

Title: X-ray structure of a ClC chloride channel at 3.0 A reveals the molecular basis of anion selectivity.

Authors: Raimund Dutzler, Ernest B Campbell, Martine Cadene, Brian T Chait, Roderick MacKinnon

Journal, date & volume: Nature, 2002 Jan 17 , 415, 287-94

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/11796999

Abstract
The ClC chloride channels catalyse the selective flow of Cl- ions across cell membranes, thereby regulating electrical excitation in skeletal muscle and the flow of salt and water across epithelial barriers. Genetic defects in ClC Cl- channels underlie several familial muscle and kidney diseases. Here we present the X-ray structures of two prokaryotic ClC Cl- channels from Salmonella enterica serovar typhimurium and Escherichia coli at 3.0 and 3.5 A, respectively. Both structures reveal two identical pores, each pore being formed by a separate subunit contained within a homodimeric membrane protein. Individual subunits are composed of two roughly repeated halves that span the membrane with opposite orientations. This antiparallel architecture defines a selectivity filter in which a Cl- ion is stabilized by electrostatic interactions with alpha-helix dipoles and by chemical coordination with nitrogen atoms and hydroxyl groups. These findings provide a structural basis for further understanding the function of ClC Cl- channels, and establish the physical and chemical basis of their anion selectivity.