Question

A researcher has designed a bacterial expression system that produces a protein of interest with a histidine affinity tag attached to the protein. Describe how the researcher can purify the protein in order to study the protein of interest further.

Answer 1

As per the question your protein of interest contains a histidine affinity tag, basically it means that there is a repetetive sequence of histidine amino acid at either N terminal of protein or at C- terminal of protein. In order to purify such type of protein from others you may use the Ni²⁺-NTA affinity chromatography .

In this chromatography per say, the Nickel is attached to the agrose gel with the help of chelation done by NTA ( Nitrloacetic acid ). So when the chelation is complete the structure of "Ni²⁺ - NTA agrose" has some gaps or vacant positions in it. The histidine residues in the hisitdine tag of the protein occupies these vacant poisitons or gaps the in the Ni²⁺ - NTA agrose gel structure. While other proteins which do not have these histidine tags will easily move through the agrose gel. So in this way you can purify your protein of interest ( containing HIS tags ) .