Methionine aminopeptidases, also designated peptidase M proteins, are members of the M24 family of proteins. This protein removes the amino-terminal methionine residue from nascent polypeptides. The active site of map contains two adjacent divalent metal ions connected by a water molecule or hydroxide ion. Recombinant E.coli map protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.