Molecular simulations to determine the chelating mechanisms of various metal ions to the His-tag motif: A preliminary study

In the present study, molecular simulations were performed to investigate the chelating mechanisms of various metal ions to the His-tag motifs with various His residues. The chelation mostly involved the i and 42 His residues for Ni2+, Zn2+, Cu2+, and Co2+, while the cooperation of 3 His residues was necessary when Fe3+ was involved in chelation with His-tags having more than 4 His residues. Metal ion was best fitted into the pocket formed by the imidazole nitrogens while it was about equally located among these nitrogen atoms. His-tag6 was found to have little effect on the structural integrity while the target protein contains more than 68 amino acid residues. Ni2+ interacted with the imidazole nitrogen of His3 in the beginning of chelation, and then entered into the pocket formed by His3 and His5 at 4 ns during the 10 ns molecular dynamics simulations. The fast chelating process resulted in successful application of IMAC techniques in efficient protein purification.