"Biological Diversity and Therapeutic Potential of Natural and Engineered Cystine Knot Miniproteins." Current Opinion in ... The growth factor cystine knot (GFCK) inhibitor cystine knot (ICK) common in spider and snail toxins Cyclic Cystine Knot, or ... Novel proteins are being added to the cystine knot motif family, also known as the C-terminal cystine knot (CTCK) proteins. ... A unique family of cyclic and knotted proteins that defines the cyclic cystine knot structural motif". Journal of Molecular ...