Related Experiment Video
Updated: Jun 23, 2026

Identification of Post-translational Modifications of Plant Protein Complexes
Published on: February 22, 2014
Circling the enemy: cyclic proteins in plant defence
1The University of Queensland, Institute for Molecular Bioscience, Brisbane, QLD 4072, Australia. d.craik@uq.edu.au
Abstract:
Cyclotides are ultra-stable plant proteins that have a circular peptide backbone crosslinked by a cystine knot of disulfide bonds. They are produced in large quantities by plants of the Violaceae and Rubiaceae families and have a role in plant defence against insect predation. As I discuss here, recent studies have begun to reveal how their unique circular topology evolved. Cyclization is achieved by hijacking existing plant proteolytic enzymes and operating them in 'reverse' to form a peptide bond between the N- and C-termini of a linear precursor. Such studies suggest that circular proteins are more common in the plant kingdom than was previously thought, and their exceptional stability has led to their application as protein-engineering templates in drug design.
More Related Videos
Related Concept Videos
Defenses Against Pathogens and Herbivores
Cell Signaling in Plants
Introduction to Plant Diversity
Plant Cell Wall
Plant Hormones
Plant Hormones

