Mechano-chemistry of the enzyme Guanylate Kinase

Department of Physics and Astronomy University of California Los Angeles - Los Angeles, CA 90095-1547, USA

^a zocchi@physics.ucla.edu

Received: 8 April 2010
Accepted: 29 June 2010

Abstract

We address the coupling of mechanics and chemistry in an enzyme through equilibrium experiments where we mechanically deform the enzyme and measure the effect on the chemical reaction it catalyzes. We use the DNA molecular spring method to exert stresses at three different specific locations on the enzyme Guanylate Kinase, and for each case determine the changes in substrates binding affinities and catalytic rate. We find that the enzyme kinetics parameters can be affected separately, depending on where the mechanical stress is applied. For one configuration the applied stress mainly affects the catalytic rate k_cat, for another it mainly affects the binding affinity of the substrate GMP. These experiments show that a stress applied by pulling two residues on the surface of the protein generally results in a strain propagating into the structure.