Dear Friends, I have been trying to purify a protein (27 kDa) which has a sumo plus 6 His-tag at N-ter giving totaly a 45 kDa protein. This protein does not express without sumo tag and has a poly basic tail (Arg and Lys) at its N-ter. It does polymerize at acidic pHs. When I tried to purify it with chelating Ni-NTA, it did not bind to the column. I thought perhaps His-tag hided somewhere in the protein and is not accessible thus, I repeated the experiments at 8 M urea. It did not make any difference; very low binding to the column with high amount of unbound protein in FT. Your advice is highly appreciated.
Regards, Jahan
