Cystine knot

Protein structural motif

A cystine knot is a protein structural motif containing three disulfide bridges. The sections of polypeptide that occur between two of them form a loop through which a third disulfide bond passes, forming a rotaxane substructure. The cystine knot motif stabilizes protein structure and is conserved in proteins across various species. There are three types of cystine knot, which differ in the topology of the disulfide bonds:The growth factor cystine knot (GFCK) inhibitor cystine knot (ICK) common in spider and snail toxins Cyclic Cystine Knot, or cyclotide

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