Binding to Imidazole Groups

Use can be made of the affinities of metals to imidazoles to modify enzyme activity. For example, site-directed mutagenesis was used to add a second histidine to a serine protease in order to enhance the interaction between a transition metal ion and the side chain of His-57 (Higaki et al, 1990). The strengths of association of metals were found to be Cu (21 yM) Ni (49 /xM) (128 p.M). This is the order of associa- 

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Gurd, 1954), though the interaction of enolase with Zn++, for instance, is stronger than that found in its non-specific binding to imidazole groups, e.g., in serum albumin (Malmstrom, 1953 personal communication, 1955). 

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