Cyanobacterial Cyclic Peptides Containing cis-Pro Conformation

More than 3,000 natural products have been identified from cyanobacteria. These natural products often displayed antiparasitic, anti-inflammatory, antimicrobial, and anticancer activities. Cyanobacterial cyclic natural products are ribosomal or nonribosomal peptides, typically containing one or more proline residues. However, the presence and population of the cis-Pro conformation are not always explicitly stated in the literature. The two proline isomers can affect protein function and interactions. This review focuses on the NMR characteristics and biosynthetic logic of cyanobacterial cyclic peptides containing cis-Pro dominant conformations, aiming to provide an overview of the cis-Pro conformations in cyanobacterial cyclic peptides. We manually reviewed the chemical structures and NMR chemical shifts of 150 cyanobacterial cyclic peptides containing proline residues, of which 51 cyclic peptides possessed cis-prolyl amide bonds. Furthermore, we explained the Pro cis/trans isomerism in cyclic peptides and discussed methods for better studying these Pro cis/trans conformations in the future.