Surface histidine mutations for the metal affinity purification of a β-carbonic anhydrase

Metal affinity chromatography using polyhistidine tags is a standard laboratory technique for the general purification of proteins from cellular systems, but there have been no attempts to explore whether the surface character of a protein may be engineered to similar affinity. We present the Arg160His mutation of Haemophilus influenzae carbonic anhydrase (HICA), which mimics the endogenous metal affinity of Escherichia coli carbonic anhydrase (ECCA). The purity and activity of the mutant are reported, and the purification is discussed. This is the first step toward developing a general method to engineer surface metal affinity for use in purification and metal labeling techniques.