In eubacteria as well as in mitochondria and chloroplasts, all nascent polypeptides are synthesized with N-formylmethionine at the N terminus. Peptide deformylase (PDF) is required for the removal of the formyl group at the N terminus in eubacteria. PDF is a metalloenzyme utilizing Fe2+ as catalytic metal whereas the Zn2+ form (presented structure) is nearly inactive. The deletion of the PDF gene was shown to be lethal for Escherichia coli. Formylation/deformylation cycle appears to be a characteristic feature of eubacteria and does not occur in the cytoplasm of eucaryotic cells. Therefore, PDF is an attractive target for the design of new antibiotics.