Purification of bovine S100A12 from recombinant Escherichia coli

S100A12, a member of the S100 family of EF-hand calcium-binding proteins, was purified from Escherichia coli cells expressing the corresponding cDNA. The procedure involved washing induced E. coli cells with EDTA-containing hypotonic solution, ion-exchange chromatography, and HPLC. Recombinant S100A12 was purified to homogeneity with the final yield around 6.7 mg per 20 ml of culture. The purified protein was identical to native S100A12 in the N-terminal amino acid sequence, lysylendopeptidase peptide mapping, mass spectrum, and Ca2+-dependent binding affinity to amlexanox, an antiallergy drug. However, the N-terminal methionine residue of the purified protein was not cleaved off as in the native protein. The method used in the present study permits the purification of recombinant S100A12 in large quantities and may also be applicable to preparation of other S100 family proteins.