The KNOTTIN database

Knottins are made from an elementary motif

  • Comparison of knottins show that only two disulfides are structurally well conserved.
  • All knottins contain a well-conserved two-disulfide structural motif.
  • Knottins might have emerged from ancestral two-disulfide proteins.
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Cystine Stabilized Beta-sheet

Disulfide Directed beta-Hairpin


The CSB motif

It has been noticed that knottins, that contain at least three disulfide bridges, are built from a possibly ancestral two-disulfide elementary motif.
One such motif has been termed the CSB (Cystine Stabilized β-sheet) motif [Heitz et al, 1999].

 
The minimum peptide, known as Min-23, correponding to the isolated CSB motif has been shown to be an autonomous folding unit with a significant thermal stability (Tm = 100 °C) [Heitz et al, 1999].
The Min-23 peptide has been used as a structural motif to build chimeras of Angiotensin-Converting Enzyme in which the JuxtaMembrane stalk is replaced by Min-23 [Schwager et al., 2001]. It is shown that, in contrast to native JuxtaMembrane stalk or to chimere using EGF, the Min-23 chimere is not cleaved inside the motif but rather next to it.
The Min-23 peptide has been used as a small and stable structural scaffold to obtain novel binding specificities by selection from a display library [Souriau et al., 2005]. It is shown that, in contrast to native JuxtaMembrane stalk or to chimere using EGF, the Min-23 chimere is not cleaved inside the motif but rather next to it.


The DDH motif

A slightly different description has also been given and termed the DDH (Disulfide-Directed β-Hairpin) motif [Wang et al., 2000].
The DDH motif contains a β-hairpin instead of a triple-stranded β-sheet.