• This knot is achieved when one disulfide bridge crosses the macrocycle formed by the two other disulfides and the interconnecting backbone.
• The knot implies that knottins contain at least 3 disulfide bridges.
• The structural family of knottins have the disulfide between cysteines III and VI (blue) going through disulfides I-IV and II-V (green).
• The growth factor cystine knots also contain a knot but the connectivity is different and they cannot be superimposed onto knottins. These proteins belong to a distinct structural family not described in this site.
• Knottins are sometime refered to as "Inhibitor Cystine Knots".
• Protease inhibitors from plants
• Peptides from the Rubiaceae and the Violaceae plant families
• Toxins from cone snail, spider, bug, horseshoe crab, scorpion
• Gurmarin-like peptides, human Agouti-related proteins
• Antimicrobial peptides
A number of small disulfide-rich proteins may look like Knottins, but are not Knottins simply because there is no knot in there.
• Small and easily accessible to chemical synthesis,
• Very stable, thanks to the high disulfide content and the knotted topology,
• Strongly sequence tolerent.