Tyrocidine biosynthesis. Tyrocidine is a cyclic decapeptide (-dPhe-Pro-Phe-dPhe-Asn-Gln-Tyr-Val-Orn-Leu-)cyc produced by B. brevis ATCC 8185 (C). The three genes (tycA, tycB, and tycC) (A) are transcribed and translated into the NRPSs TycA (124 kDa), TycB (405 kDa), and TycC (724 kDa), which comprise one, three and six modules, respectively, and accomplish the ordered synthesis via the linear decapeptide (B).