Gas Channels for NH 3 : Proteins from Hyperthermophiles Complement an Escherichia coli 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°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 .