This glycine-rich peptide antibiotic inhibits DNA replication in many enteric bacteria, that leads to induction of the SOS repair system, massive DNA degradation and cell death. B17 inhibits type II topoisomerase by trapping an enzyme - DNA cleavable complex. The processed N-terminus does not resemble a typical secretion signal sequence. Maturation of thiazole and oxazole containing antibiotics involves the enzymatic condensation of a Cys, Ser or Thr with the alpha-carbonyl of the preceding amino acid to form a thioether or ether bond, then dehydration to form a double bond with the alpha-amino nitrogen. Thiazoline or oxazoline rings are dehydrogenated to form thiazole or oxazole rings.