DFT Study on the His-Tag Binding Affinity of Metal Ions in Modeled Hexacationic Metal Complexes

Area of Science:

• Biochemistry
• Computational Chemistry
• Protein Engineering

Background:

• Histidine oligomers (His-tags) are essential affinity tags for recombinant protein purification.
• His-tags facilitate purification by coordinating with metal ions (Cu²⁺, Zn²⁺, Ni²⁺) on resins.
• The precise coordination chemistry of His-tags with metal ions remains incompletely understood.

Purpose of the Study:

• To model the chemical structure of metal-coordinating His-tags.
• To elucidate metal preferences for enhanced binding affinity.
• To determine structural alterations upon metal coordination.

Main Methods:

• Density Functional Theory (DFT) at the B3LYP/6-31g (d, p) level with implicit water (IEFPCM) solvent model.
• Modeling of the resin as an oxalaldehyde group.
• Analysis of NBO energies to estimate metal electron donor/acceptor activity.
• Calculation of complexation enthalpies for metal-resin-hexahistidine interactions.

Main Results:

• Nickel (Ni²⁺) exhibits the highest affinity for the recombinant six-histidine tag (6His-tag).
• Computational modeling provided insights into metal coordination preferences and structural changes.
• The study quantified binding affinities, aiding in optimizing protein purification strategies.

Conclusions:

• Ni²⁺ is the preferred metal ion for 6His-tag affinity purification.
• Understanding metal coordination chemistry can improve His-tag based purification techniques.
• This research provides a computational basis for selecting optimal metal resins for His-tag purification.