Modular structure of NRPSs. Module and domain structure of NRPS. Top, center: one complete NRPS consisting of three modules. Bottom: enzymatic domains contained in a complete module: Cond: Condensation domain (the detail shows the approximate positions of the seven motifs shown in detail in Fig. 2), Adenyl: Adenylation domain (A domain), N-Meth: N-methylation domain (optional – does not appear in all NRPS), PCP: Thiolation domain (T domain or Peptidyl Carrier Protein domain), Epi: Epimerization domain (optional). Other optional domains are: Heterocyclization, Oxidation, Reduction and Formylation domains.