Abstract
A special family of inhibitors, known as the serpins, has evolved an extraordinary mechanism to enable the control of the proteolytic pathways essential to life. The serpins undergo a profound change in conformation to entrap their target protease in an irreversible complex. The solving of the structure of this complex now completes a video depiction of the changes involved. The serpin, just like a mousetrap, is seen to change with a springlike movement from an initial metastable state to a final hyperstable form. The structure shows how this conformational shift not only inhibits the protease but also destroys it. A bonus from these structural insights is the realisation that a number of diseases, as diverse as thrombosis, cirrhosis and dementia, all share a common mechanism arising from similar mutations of different serpins.