Enzymes are like nanomachines made out of proteins, and it can be very important medically to find ways to turn them on and off. Now Giovanni Zocchi in the Department of Physics and Astronomy and colleagues at the University of California, Los Angeles, have discovered a way to do this mechanically.
The researchers attached a "molecular spring" in the form of DNA to the enzyme guanylate kinase, coupling two parts of the protein (see figure). They were then able to change the stiffness of the spring by altering external DNA concentrations and so control the enzyme's activity.
The action of guanylate kinase depends on its specific form, which the researchers compare to a vice, with the enzyme being active or "on" when the jaws of the vice come closer. By changing the stiffness of the spring, the team could control the mechanical tension between two points on the enzyme's surface, and thereby open and close the jaws. Measurements of the activity of the enzyme, which catalyses phosphate transfer between certain macromolecules, then revealed that they could indeed turn the enzyme on and off reversibly. The net effect was chemical control of a single protein by mechanical means.
Further reading
Brian Choi et. al. 2005 Phys. Rev. Lett. 95 078102.