Inhibitor cystine knot

Knottin Structure

An inhibitor cystine knot (ICK) is a structural motif found in certain proteins that confers exceptional stability and resistance to degradation. Proteins containing the ICK motif are characterized by a specific arrangement of disulfide bonds that form a knot-like structure, contributing to their robustness.

Structure

The hallmark of an inhibitor cystine knot is the presence of three disulfide bonds that create a unique arrangement where one disulfide bond penetrates through a macrocycle formed by the other two disulfide bonds. This arrangement results in a highly stable and compact structure that is resistant to proteolytic degradation.

Function

Proteins with the inhibitor cystine knot motif are often found in nature as potent inhibitors of enzymes or receptors. The structural stability provided by the ICK motif allows these proteins to withstand harsh conditions and maintain their inhibitory activity over time.

Examples

One well-known example of a protein containing the inhibitor cystine knot motif is Kalata B1, a cyclotide found in certain plants. Kalata B1 exhibits a range of biological activities, including antimicrobial and uterotonic properties, attributed to its unique structure and stability conferred by the ICK motif.

Applications

Due to their stability and bioactivity, proteins with the inhibitor cystine knot motif have attracted interest for various biotechnological applications. Researchers are exploring the potential of ICK-containing proteins in drug development, particularly as novel therapeutics for conditions that require highly stable and potent inhibitors.

See also

• Cyclotide
• Disulfide bond
• Protein structure