Evaluation of employing poly-lysine tags versus poly-histidine tags for purification and characterization of recombinant copper-binding proteins

Both poly-lysine tags and poly-histidine tags facilitate one-step protein purification. The former exhibits no detectable affinity for Cu(I) or Cu(II) while the latter possesses sub-nanomolar affinity for Cu(II) and sub-picomolar affinity for Cu(I). Consequently, poly-histidine tags may need to be removed for proper characterization of the purified protein.76