ECC 1989
 
p. 319 Bioelectrochemistry and Bioenergetics, 21 (1989)
 
319-331 A section of J. Electroanal. Chem., and constituting Vol. 275 (1989) Elsevier Sequoia S.A., Lausanne - Printed in the Netherlands
 
Electroconformational coupling (ECC): an electric field induced enzyme oscillation for cellular energy and signal transductions* Tian Yow Tsong, Dao-Sheng Liu and Francoise Chauvin Department of Biochemistry, University of Minnesota College of Biological Sciences, 1479 Gortner Avenue, St. Paul, MN 55108 (U.S.A.)
 
Aldolfas Gaigalas and R. Dean Astumian, National Institutes of Standards and Technology, Chemical Process Metrology Division, Gaithersburg, MD 20899 (U.S.A.)
 
(Received 20 November 1988; in revised form 4 February 1989)     

      Abstract
 
      Previous work has shown that membrane ATPases can extract free energy from applied oscillating electric fields for doing chemical work, e.g. to synthesize ATP from ADP and P(i) or to transport Rb and Na ions against their respective electrochemical gradient. Data of these experiments are briefly reviewed. Electroconformational Coupling (ECC) is used to interpret these results. Computer analysis of a four state cyclic enzyme mechanism reproduces many experimental features. It is shown that a coulombic interaction between an enzyme and an alternating electric field (ac) can cause the enzyme to oscillate between different conformational states. If the frequency of the applied field matches the kinetic characteristics of the system and the amplitude matches the energy required for inducing productive catalytic cycling, a phenomenological resonance between catalytic reaction and the periodic field is generated. A condition necessary for achieving energy coupling is the kinetic bias arising from the binding energy of the ligand. Analysis indicates that only dynamic electric fields, i.e. oscillating or fluctuating fields, can propel the cyclic reaction of the enzyme catalysis, and thus be effective for transducing energy. A stationary transmembrane electric field must be modulated, e.g. by opening and closing of an ion channel, to become oscillatory in order to produce the same effect. We propose that ECC is a fundamental process of cellular energy and signal transductions. Here, many membrane associated events are reduced to Michaelis-Menten types of enzyme catalytic reactions and they are thus amenable to the quantitative analysis of chemical kinetics.

      Introduction
 
     Electrochemical potential of ions have been postulated to play a major role in free energy transductions and information transfer of cells. In neural transmission, Na and K currents are responsible for the generation and propagation of the action potential [1,2]. In mitochondrial ATP synthesis, the proton gradient across the inner membrane is the high energy intermediate, which, upon translocation of protons along the electrochemical gradient, transfers its potential energy to ATPase for the synthesis of ATP [3-8]. In photosynthetic processes, the energy of a photon is used to pump a proton into an energy reservoir and ATP synthase then uses the electrochemical potential energy of the proton for synthesis of ATP [7,9,10]. Notwithstanding, there is no compelling evidence which would exclude a direct energy transfer between the electric field and a protein, thus allowing a temporary storage of energy in the conformational states of the protein [11]. Previously, we proposed a mechanism, Electroconformational Coupling (ECC), to test the feasibility of direct energy transaction between a transmembrane electric field and an enzyme conformational equilibrium for driving ion pumps and ATP synthesis [12-15]. Here we will summarize new experimental evidence and analysis based on the concept of ECC. We will examine and compare the ECC model and the common enzyme catalytic process as exemplified by the Michaelis-Menten Mechanism.