FIGURE 7.

Putative enzymes involved in the cyclotide bioprocessing. In C. ternatea (Fabaceae), the signal peptidase I (SPase I) responsible for ER excision is also the N-terminal processing enzyme of cliotides. In the Rubiaceae and Violaceae families, unknown enzyme(s) are required for the N-terminal cleavage of the cyclotide domain. The C termini of cyclotides in these three families are processed by AEPs because of the highly conserved Asn/Asp residue at the processing site. The sequence logos were built using WebLogo server (24, 58).