Ion-binding properties of the ClC chloride selectivity filter.
The ClC channels are members of a large protein family of chloride (Cl-) channels and secondary active Cl- transporters. Despite their diverse functions, the transmembrane architecture within the family is conserved. Here we present a crystallographic study on the ion-binding properties of the ClC selectivity filter in the close homolog from Escherichia coli (EcClC). The ClC selectivity filter contains three ion-binding sites that bridge the extra- and intracellular solutions. The sites bind Cl- ions with mM affinity. Despite their close proximity within the filter, the three sites can be occupied simultaneously. The ion-binding properties are found conserved from the bacterial transporter EcClC to the human Cl- channel ClC-1, suggesting a close functional link between ion permeation in the channels and active transport in the transporters. In resemblance to K+ channels, ions permeate the ClC channel in a single file, with mutual repulsion between the ions fostering rapid conduction.
Lobet
Séverine
S
Department of Biochemistry, University of Zürich, Zürich, Switzerland.
Dutzler
Raimund
R
D001966:Bromine / Q000737:chemistry; D002414:Cations, Monovalent / Q000737:chemistry; D018118:Chloride Channels / Q000737:chemistry* / Q000235:genetics; D002713:Chlorine / Q000737:chemistry; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D009154:Mutation; D011487:Protein Conformation
D002414:Cations, Monovalent; D018118:Chloride Channels; C508370:ClC protein, E coli; D029968:Escherichia coli Proteins; D002713:Chlorine; D001966:Bromine