Research Note | Published:

Protein Stabilization by Engineered Metal Chelation

Bio/Technology volume 9, pages 994995 (1991) | Download Citation



A ligand can shift a protein's folding/unfolding equilibrium by binding with higher affinity to the native state. A metal–chelating site consisting of two histidines separated by three residues (His–X3–His) engineered into an α–helix provides a general and easily–implemented means for protein stabilization by this mechanism. We have tested this approach with the iso–1–cytochrome c of Saccharomyces cerevisiae substituted with histidine at positions 4 and 8 in its N–terminal α–helix. One mM Cu(II) complexed to iminodiacetate stabilizes the cytochrome c variant by ca. 1 kcal/mol, as determined by guanidinium chloride–induced unfolding. The protein's folding/unfolding equilibrium is shifted by a free energy equal to that calculated from the metal ion's preferential binding to the native protein. Given the ubiquity of surface α–helices and the additional possibility of inserting di–histidine chelating sites into turns and β–structures, we conclude that this is a useful method for protein stabilization.

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    • Frances H. Arnold

    Corresponding author.


  1. Division of Chemistry and Chemical Engineering, 210-41, California Institute of Technology, Pasadena, CA 91125.

    • James T. Kellis Jr.
    • , Robert J. Todd
    •  & Frances H. Arnold


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