1. Department of Biochemistry, Howard Hughes Medical Institute
2. Rosenstiel Basic Medical Science Research Center and W. M. Keck Institute for Cellular Visualization, Brandeis University , Waltham, Massachusetts 02454, USA

Correspondence to: Joseph A. Mindell¹ Correspondence and requests for materials should be addressed to J.A.M. (e-mail: Email: jmindell@brandeis.edu).

Abstract

Virtually all cells in all eukaryotic organisms express ion channels of the ClC type, the only known molecular family of chloride-ion-selective channels. The diversity of ClC channels highlights the multitude and range of functions served by gated chloride-ion conduction in biological membranes, such as controlling electrical excitability in skeletal muscle, maintaining systemic blood pressure, acidifying endosomal compartments, and regulating electrical responses of GABA (-aminobutyric acid)-containing interneurons in the central nervous system¹. Previously, we expressed and purified a prokaryotic ClC channel homologue². Here we report the formation of two-dimensional crystals of this ClC channel protein reconstituted into phospholipid bilayer membranes. Cryo-electron microscopic analysis of these crystals yields a projection structure at 6.5 Å resolution, which shows off-axis water-filled pores within the dimeric channel complex.