TY - JOUR
T1 - Catalytic wheel, Brownian motor, and biological energy transduction
AU - Tsong, Tian Yow
AU - Chang, Cheng-Hung
PY - 2005/2/1
Y1 - 2005/2/1
N2 - An enzyme turns over, or recycles during each catalytic process. It is a catalytic wheel, analogous to a motor, or an engine. The fuel, or the driving force for the wheel, is the free energy of the substrate (S) to product (P) conversion (ΔGR), or a free energy output of a coupled chemical reaction. When ΔGR of the S → P reaction is negative the reaction is spontaneous and the down-hill wheel motion requires no external input of energy. When ΔGR is positive the wheel must turn uphill against a workload, a reaction that produces energy must be coupled to the wheel. The synthesis of ATP from ADP and Pi in a cell is an uphill reaction and the energy required for the synthesis is derived from the dissipation of a proton gradient, or an electric potential. This article focuses on mechanisms of action of the uphill catalytic wheels. It is shown that the coupling of an external energy source to an uphill catalytic wheel can be done, with nearly 100% efficiency, by mechanisms of the Brownian Motor. Theory of electroconformational coupling (TEC) is used to construct a Brownian motor, and electric activation of an ion pump, Na, K-ATPase is used to demonstrate its basic principles. A TEC Motor has three essential elements: 1) the ability of the protein to interact with an electric field, 2) existence of at least two conformations of protein that oscillate or fluctuate on interaction with the applied field, and 3) a built-in asymmetry in the molecular interactions with substrate and product. It is shown that the TEC Motor is a generic model and applicable to other types of biological energy transducers.
AB - An enzyme turns over, or recycles during each catalytic process. It is a catalytic wheel, analogous to a motor, or an engine. The fuel, or the driving force for the wheel, is the free energy of the substrate (S) to product (P) conversion (ΔGR), or a free energy output of a coupled chemical reaction. When ΔGR of the S → P reaction is negative the reaction is spontaneous and the down-hill wheel motion requires no external input of energy. When ΔGR is positive the wheel must turn uphill against a workload, a reaction that produces energy must be coupled to the wheel. The synthesis of ATP from ADP and Pi in a cell is an uphill reaction and the energy required for the synthesis is derived from the dissipation of a proton gradient, or an electric potential. This article focuses on mechanisms of action of the uphill catalytic wheels. It is shown that the coupling of an external energy source to an uphill catalytic wheel can be done, with nearly 100% efficiency, by mechanisms of the Brownian Motor. Theory of electroconformational coupling (TEC) is used to construct a Brownian motor, and electric activation of an ion pump, Na, K-ATPase is used to demonstrate its basic principles. A TEC Motor has three essential elements: 1) the ability of the protein to interact with an electric field, 2) existence of at least two conformations of protein that oscillate or fluctuate on interaction with the applied field, and 3) a built-in asymmetry in the molecular interactions with substrate and product. It is shown that the TEC Motor is a generic model and applicable to other types of biological energy transducers.
UR - http://www.scopus.com/inward/record.url?scp=24644445600&partnerID=8YFLogxK
M3 - Review article
AN - SCOPUS:24644445600
SN - 0577-9073
VL - 43
SP - 273
EP - 284
JO - Chinese Journal of Physics
JF - Chinese Journal of Physics
IS - 1 II
ER -