Abstract: Recombinant fusion proteins which comprise a biologically active polypeptide portion and metal chelating peptide are disclosed. The fusion proteins contain metal chelating peptides which have at least three and preferably six alternating histidine residues. Fusion proteins which contain metal chelating peptides that are substrates for dipeptidylpeptidase I are also disclosed. Additionally, a method of obtaining desired polypeptides by producing recombinant fusion proteins and purifying them with immobilized metal ions is disclosed. A kit for purifying desired polypeptides is also disclosed.