Fig. 1. Structures of AMPD G3KL (ref. 37), bicyclic peptide BCP27c (calmodulin binder, ref. 42), and AMBPs 27b and 62b identified in this study. The peptides are shown with amino acids in one letter code with branching residues in italics and peptide bonds as arrows in C → N direction. Z = branching γ-homoglutamic acid (formed by ClAc ligation of cysteine).