Expression of the peanut peroxidase cDNA in Escherichia coli and purification of the protein by nickel affinity

A cDNA sequence containing the entire cationic peanut (Arachis hypogaea) peroxidase (EC 1.11.1.7, CPRX) coding sequence, including a 22-amino acid signal peptide, was extended using a synthetic oligonucleotide with a six histidine-tag at the C-terminal and expressed in bacteria. The expressed protein was purified on a Ni2+-nitrilotriacetic acid (NTA) column and the resulting protein had a molecular mass corresponding to an unglycosylated polypeptide. Western blot analysis showed the protein to be recognized by polyclonal antibodies raised against native CPRX and monoclonal antibodies specifically recognizing six histidine-tag, but not by monoclonal antibody which recognizes carbohydrate-containing epitopes of CPRX.