Purification and functional reconstitution of the human CHIP28 water channel expressed in Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae was used for heterologous expression of the human CHIP28 water Aquaporin-1 channel (Aquaporin-1). A nine-aminoacid epitope of the influenza hemagglutinin protein (HA epitope), recognized by the monoclonal antibody 12CA5, was chosen to tag CHIP28 at its N-terminus. Epitope-tagged CHIP28 was purified from yeast extracts by immunochromatography on protein A/12CA5-coupled beads, after KI extraction and detergent solubilization, then concentrated by anion exchange chromatography. Purified protein was reconstituted in proteoliposomes and was shown to function as a water channel by stopped-flow spectrophotometry. This study demonstrates that the yeast has the capacity to produce functional aquaporins at levels sufficient for biochemical and biophysical analyses. (C) 1997 Academic Press.