Recombinant expression, purification and characterization of Kch, a putative Escherichia coli potassium channel protein

The Escherichia coli gene kch, similar in primary structure to eukaryotic voltage-gated potassium channels, was cloned and overexpressed in E. coli. The protein was solubilized from the plasma membrane with dodecylmaltopyranoside, lauryldimethylamine oxide or N-laurylsarcosine and was purified in milligram amounts by imidazole elution from a nickel-chelate column. The molecular mass of the purified protein in a number of detergents with 12 carbon atom chains suggests that rKch forms primarily tetramers of the 50 kDa monomers. CD spectroscopy of the purified protein indicates a significant α-helical content that is preserved upon addition of SDS.