Protein-protein interaction studies using immobilized oligohistidine fusion proteins

Using a human transcription factor, upstream stimulatory factor, as a model system, we developed a method for the rapid and efficient purification of proteins that interact with a cloned polypeptide expressed as a fusion with an oligohistidine domain. The complex between the oligohistidine fusion protein and its interacting partner was loaded onto a column of chelating resin charged with Ni2+. The bound complex could be eluted as a whole with high concentrations of imidazole. Alternatively, the secondary protein could be released separately using appropriate elution conditions. This procedure is both simple and efficient, and it presents distinct advantages over other affinity purification methods. In addition, this same method can be used to study protein-protein interactions.