Knottins display a variety of biological functions


  • ‣ Some knottins are thought to perform their action via interaction with a receptor.
  • ‣ This has led several authors to use the slightly restrictive name "Inhibitor Cystine Knot" (ICK)
  • ‣ Different activities are located on different parts of the molecules, and almost all Knottin loops have been implied in one ore more function.
  • ‣ The major known biological functions exerted by Knottins are briefly outlined below.
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Analgesics

Anthelmintic

Anti-ED

Antimalarial

Antimicrobials

Antitumors

Protease inhibitors

Toxins

Insecticids

Others

Insecticids

Few Knottins have shown insecticidal activity

  • Orally active insecticidal peptide (OAIP-1) (PDB ID: 2LL1) from venom of the Australian tarantula Selenotypus plumipes [Hardy et al., 2013].
  • J-Atracotoxin-HV1C (PDB ID: 1DL0)
  • Kalata B1 and other cyclotides display insecticidal activities. It has been shown that the insecticidal and hemolytic activity of kalata B1 are both dependent on a cluster of hydrophilic residues separate from the membrane binding face. It is postulated that specific self-association, in combination with membrane binding mediates cyclotide bioactivities [Simonsen et al., 2008]. Kalata B1 has been shown to disrupt epithelial cells in the midgut of lepidopteran larvae and consequently to negatively affect nutrient uptake [Barbeta et al., 2008].
  • α-Amylase inhibitor AAI (PDB ID: 1CLV)
  • Plant proteinase inhibitors: Leaf-specific over-expression of the potato inhibitor PI-II and of the knottin PCI (carboxypeptidase inhibitor) results in increased resistance to Heliothis obsoleta and Liriomyza trifolii larvae in homozygote tomato lines expressing high levels of the transgenes [Abdeen et al., 2005].