Detection and Immobilization of Proteins Containing the 6xHis Tag

Many systems have been developed for the heterologous expression of recombinant proteins. They are often based on the fusion of the protein of interest with a naturally occurring protein (glutathione S -transferase [1 ], maltose binding protein [2 ], or protein A [3 ]) and using their natural affinity to substrates (glutathione, amylose, or immunoglobulins) coupled to columns in the purification step. Problems with these systems are that the affinity tag may affect protein structure and function, and that proteins in insoluble fractions cannot be adequately purified.