Gas Channels for NH3: Proteins from Hyperthermophiles Complement an Escherichia coli Mutant
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.
The author reports on a rare case of local amyloidosis (amyloid tumour) of the stomach. The first electron-microscopic study of such case was performed by her. She observed a large number of microfilaments in the mucus producing cells of the stomach mucosa, and assumed this to be indicative of a pathologic mucus secretion. The epithelial cells involved also changes indicating the disorder of protein secretion. She treats in detail the electron-microscopic characteristics of cellular elements found in amyloid. The closest relationship to amyloid deposits was shown by myofibroblasts. They probably play an important role in the formation of local amyloid.