Figure 1.

3D structure (left) and amino acid sequence (right) of native kalata B1 (PDB ID: 1nb1) showing the knotted, cyclic nature of cyclotides. All cyclotides contain six conserved cysteine residues, and the backbone segments in between are termed “loops”. The disulfide connectivity is shown by lines connecting the cysteine residues, the cysteine residues are labeled I–VI, and the six loops are identified. The peptide is processed from a larger linear precursor^[6] with ligation at Gly1 to Asn29 (indicated by circles).