the precursor contains serines , threonines , and cysteines at positions that permit them to undergo a series of dehydration and cross-linking steps to give the mature antibiotic peptide which contains the unusual amino acids lanthionine , beta-methyllanthionine , d-alanine , dehydroalanine , and dehydrobutyrine .
C0002520
amino acids
C0001898
alanine