18S,21S,24S,27R,32aS) -9-(2-amino-2-oxoethyl)- 21-(3-aminopropyl)- 3,6,27-tribenzyl-15- (4-hydroxybenzyl)-24-isobutyl- 18-isopropyl- 1,4,7,10,13,16,19,22,25,28- decaoxodotriacontahydropyrrolo[1,2-a] [1,4,7,10,13,16,19,22,25,28] decaazacyclotriacontin- Tyrocidine is a mixture of cyclic decapeptides produced by the bacteria Brevibacillus brevis found in soil.

Parts of its sequence are identical to gramicidin S. In 1939, the American microbiologist René Dubos discovered the soil microbe Bacillus brevis.

Tyrocidine has a unique mode of action in which it disrupts the cell membrane function, making it a favorable target for engineering derivatives.

[6] Its biosynthesis is via an enzymatic assembly consisting of 3 peptide synthetase proteins, TycA, TycB, and TycC, which contain 10 modules.

It has been suggested that the tandem transporters play a role in conferring resistance in the producer cell through tyrocidine secretion.

TycF has been identified as a thioesterase (TE) and is similar to other TEs in bacterial operons used for encoding peptide synthetases.

This is accomplished through the subdomains for adenylation (A), peptityl carrier protein (PCP), condensation (C), and depending on the amino acid position, an epimerization (E).

[8] Elongation of the peptide chain is achieved through condensation of the upstream PCP onto an adjacent downstream PCP-bound monomer.

In the case of tyrocidine, ring closure has been shown to be highly favorable due to 4 H-bonds helping the decapeptide backbone to adopt a stable conformation (See figure 5).

Isolated tyrocidine (Tyc) TE domains can be used to cyclize chemically derived peptidyl-thioester substrates, providing a powerful route to new cyclic compounds.