Triterpenoid saponins from Bellium bellidioides

Alanine Scanning Mutagenesis of the Prototypic Cyclotide Reveals a Cluster of Residues Essential for Bioactivity

“…Kalata B1 was identified as a uterotonic component of the plant, but its unusual macrocyclic nature (2) and the fact that it was just one member of a large family of related macrocyclic peptides were elucidated only recently (3). Cyclotides have now been reported in several other species of the Rubiaceae (coffee) family (4,5) and in all tested members of the Violaceae (violet) plant family (3,6,7) bringing the number of known cyclotides to over 100. Individual plants contain a suite of dozens of cyclotides, and analyses of crude plant extracts have suggested that thousands more cyclotide sequences await discovery (8,9), potentially making them one of the largest known families of plant proteins.…”

“…In addition to their uterotonic activity (12), hemolytic (6), anti-HIV 4 (13), anti-bacterial (14), anti-tumor (15), anti-fouling (16), and insecticidal (17) activities have been reported. The mechanism(s) of action of these activities are unknown but may involve interactions with membranes (18,19), possibly via selfassociation of cyclotides to form multimeric species (20).…”

Structure and Activity of the Leaf-Specific Cyclotide vhl-2

“…[4] It is believed that the compact CCK motif of cyclotides is responsible for their exceptional resistance against chemical, thermal, and proteolytic degradation. [5] Cyclotides display a diverse range of biological activities, including uterotonic, [6] haemolytic, [7][8][9] neurotensin antagonistic, [10] HIV inhibitory, [11] antimicrobial, [12] cytotoxic, [13] antifouling, [14] and trypsin inhibitory activities. [15] In addition, kalata B1 and B2 have been shown to inhibit the growth and development of Helicoverpa punctigera and H. armigera larvae, suggesting that cyclotides function as insecticidal agents as part of plant defence systems.…”

Circular Proteins in Plants

“…These circular proteins include kalata B1 (1), the circulins (2, 3), and cyclopsychotride A (4) from the Rubiaceae family, and various peptides from plants in the Violaceae family (3,(5)(6)(7)(8). They contain ϳ30 amino acids, including six highly conserved cysteine residues that form three structurally important disulfide bonds.…”