Production of recombinant proteins. (A). Analysis of partially purified ButaIT by SDS-PAGE (Tris-Tricine buffer system); gel stained with Coomassie blue. Arrow indicates ButaIT polypeptide, based on reaction with anti-(his)6 antibodies on Western blot. (B), (C). Purification of ButaIT/GNA by gel filtration. Following partial purification by phenyl-Sepharose chromatography recombinant proteins were loaded onto a Sephacryl S200 column equilibrated in PBS buffer. (B) absorbance profile and (C) corresponding fractions run on SDS-PAGE (15 % acrylamide gel, stained with Coomassie blue). The arrow depicts purified ButaIT/GNA.