Fig. 1

General biosynthetic pathway of orbitides, abstracted from [3]. The precursor protein mainly comprises a signal sequence (SIG, yellow), a leader peptide (LEA, orange), the core peptide region (CPR, purple) and the recognition sequence (REC, blue). Each CPR is flanked by the N-terminal region (NTR, grey) and C-terminal region (CTR, green). The precursor protein undergoes post-translational modification that cyclizes the CPR into the mature cyclized product. In this case, the CPR is a linusorb B1 (LO-B1) domain in which the N-terminal methionine (M) and C-terminal isoleucine (I) are linked to form the structural formula as displayed