syn -Elimination of glutamylated threonine in lanthipeptide biosynthesis.

Methyllanthionine (MeLan) containing macrocycles are key structural features of lanthipeptides. They are formed typically by anti -elimination of L-Thr residues followed by cyclization of L-Cys residues onto the ( Z )-dehydrobutyrine (Dhb) intermediates. In this report we demonstrate that the biosynthesis of lanthipeptides containing the D- allo -L-MeLan macrocycle such as the morphogenetic lanthipeptide SapT proceeds through ( E )-Dhb intermediates formed by net syn -elimination of L-Thr.