Gas Channels for NH ₃ : Proteins from Hyperthermophiles Complement an <i>Escherichia coli</i> Mutant

Abstract

Ammonium transport (Amt) proteins appear to be bidirectional channels for NH(3). The amt genes of the hyperthermophiles Aquifex aeolicus and Methanococcus jannaschii complement enteric amtB mutants for growth at 25 nM NH(3) at 37 degrees C. To our knowledge, Amt proteins are the first hyperthermophilic membrane transport proteins shown to be active in a mesophilic bacterium. Despite low expression levels, His-tagged Aquifex Amt could be purified by heating and nickel chelate affinity chromatography. It could be studied genetically in Escherichia coli.