Charge - Field Interactions in Cell Membranes and Electroconformational Coupling: Theory for the Interactions Between Dynamic Electric Fields and Membrane Enzymes
Free energy can be transduced from nonstationary electric fields to drive the synthesis of ATP or the formation and maintenance of concentration gradients across membranes. Even electrically silent reactions can be driven against equilibrium by the nonlinear interaction between a dynamic electric field and a membrane enzyme. There are two conditions necessary for an enzyme to transduce free energy in an external field to its output reaction. First, some conformational changes within the catalytic cycle of the enzyme must involve the intramolecular movement of charge or a change in the dipole moment of the enzyme. Second, the affinity of the enzyme for substrate must be much different than the affinity for product. Based on these concepts, we will compare the kinetic requirements which optimize a protein for transduction of free energy with those which optimize a protein for rapid catalysis. This model serves to bridge the classical chemiosmotic mechanism for free energy transduction, with models based on energy dependent enzyme conformational changes. Our electroconformational coupling model explains free energy transduction in terms of the molecular mechanisms of enzyme catalysis.
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