This is the first cyclic peptide antibiotic used clinically. The second and seventh residues of this cyclic peptide are Ornithines, an analog of lysine (one CH2 shorter). They are represented here with lysines. In addition, residue F is a D-amino acid. Even earlier reports are in Russian. Sergiev PG summarized some results on the peptide Science_direct. See also Biochem J. 1945;39(4):363-7. Pub-Med. Both X-ray and NMR have been used for stuctural studies (NMR+x).
AMPs in use: Gramicidin S was used to treat wounds and is still in use in topical ointments and eye drops. The peptide has antibiofilmB effect on E. faecalis (Jayaraman A et al., 1999) and has been successfully treated infected root canals of patients (Berditsch et al., 2016). It shows synergistic effects with polymyxin B against P. aeruginosa (Berditsch et al., 2015). Updated Jan2014; Ref Jan2014; 9/2016; 12/2016; 10/2017. GW.