IWNET12
IWNET12
Active transport of the Calcium pump: Introduction of the tempera-
ture dierence as a driving force
Anders Lervik1
1 Department of Chemistry Norwegian University of Science and Technology N-7491 Trondheim, Norway
Abstract
The kinetic cycle description of ion pumping proteins does not include a temperature dierence as a driving
force, even though proteins such as the Ca2+-ATPase ion pump is known to generate heat and participate in
thermogenesis. We analyze the kinetic cycle for the operation of the Ca2+-ATPase ion pump using two dierent
frameworks: the diagram method of Hill [1] and mesoscopic non-equilibrium thermodynamics [2]. We compare
these two descriptions and we discuss how a temperature dierence and the corresponding heat ux can be
introduced.
We then compare these descriptions with a mesoscopic non-equilibrium thermodynamic description which is
not based on a kinetic cycle [3], and show that the kinetic and the mesoscopic pictures are in accordance with
each other.
We also show how the mesoscopic approach can be used to identify the slow and fast steps of the model in terms
of activation energies, and how this can be used to simplify the kinetic diagram.
References
[1] T. L. Hill (1989) Free Energy Transduction and Biochemical Cycle Kinetics. Springer-Verlag, New York,
USA
[2] A. Lervik, D. Bedeaux and S. Kjelstrup (2012) Kinetic and mesoscopic non-equilibrium description of the
Ca2+ pump: a comparison, Eur Biophys J, DOI: 10.1007/s00249-012-0797-5
[3] D. Bedeaux and S. Kjelstrup (2008) The Measurable Heat Flux That Accompanies Active Transport by
Ca2+-ATPase. Phys Chem Chem Phys 10:73047317
E-mail: anders.lervik@chem.ntnu.no

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