Expression, purification, and initial structural characterization of YadQ,a bacterial homolog of mammalian ClC chloride channel proteins

YadQ of Escherichia coli is a homolog of the mammalian chloride channels of the ClC family, The yadQ gene was cloned as a fusion protein with a hexahi stidine tag and tobacco etch virus protease site for the removal of the tag , The protein was expressed in the membrane of E, coli and extracted with d ecylmaltoside, Purification was achieved by metal affinity chromatography f ollowed by cation exchange, Circular dichroism revealed a high alpha-helica l content. Size exclusion chromatography suggests that YadQ forms dimers, T he similarity in primary, secondary, and quaternary structure and the abili ty to recombinantly express YadQ in the cell membrane make the protein a go od candidate for the structural study of CIC chloride channels. (C) 2000 Fe deration of European Biochemical Societies.