lantibiotics are ribosomally synthesized and post - translationally modified peptide antibiotics containing the characteristic thioether cross - links lanthionine and methyllanthionine . to date , no analogues of lantibiotics that contain nonproteinogenic amino acids have been reported . in this study , in vitro - reconstituted lacticin 481 synthetase was used in conjunction with synthetic peptide substrates containing nonproteinogenic amino acids to generate 11 analogues of lacticin 481 . 
 these analogues contained sarcosine and aminocyclopropanoic acid in place of gly5 , d - valine at position 6 , 4-cyanoaminobutyric acid in place of glu13 , 3-homoarginine at the position of asn15 , n - butylglycine and -ala at met16 , naphthylalanine ( nal ) at trp19 , 4-pyridynylalanine ( pal ) at phe21 , and homophenylalanine ( hphe ) at phe23 . 
 of these analogues , the trp19nal and phe23hphe mutants provided zones of inhibition larger than the parent compound in agar diffusion assays against the indicator strains lactococcus lactis hp and bacillus subtilis 6633 . 
 these two compounds also demonstrated improved mic values against liquid cultures of l. lactis hp .