Protein domains/Affinity/Overview

Protein tags and modifiers are short peptide sequences cloned in frame with protein coding sequences that change the protein's behavior. Affinity tags are generally appended to the N- or C-terminus of proteins to enable ready purification of the protein from cells.

Generally, cells expressing the protein fused to an affinity tag are pelleted, lysed, and applied to a column, resin or other solid support that displays a ligand to the affinity tags. The solid support is washed several times with buffer to eliminate unbound proteins. Then the protein of interest is eluted from the solid support via a buffer that causes the affinity tag to dissociate from the ligand resulting in a purified protein.

There are several different affinity tags available for purification. Each has benefits and advantages depending on your protein of interest and the cell from which you are purifying it.