Thermodynamics Research Today is a free monthly online journal that collates and summarizes the latest research about Thermodynamics, including details on enthalpy, entropy, energy transitions.

Thermodynamics of the dimer-decamer transition of reduced human and plant 2-cys peroxiredoxin.

Barranco-Medina S, Kakorin S, Lázaro JJ, Dietz KJ

Biochemistry and Physiology of Plants, Faculty of Biology-W5, Bielefeld University, 33501 Bielefeld, Germany.

Isothermal titration calorimetry (ITC) is a powerful technique for investigating self-association processes of protein complexes and was expected to reveal quantitative data on peroxiredoxin oligomerization by directly measuring the thermodynamic parameters of dimer-dimer interaction. Recombinant classical 2-cysteine peroxoredoxins from Homo sapiens, Arabidopsis thaliana, and Pisum sativum as well as a carboxy-terminally truncated variant were subjected to ITC analysis by stepwise injection into the reaction vessel under various redox conditions. The direct measurement of the decamer-dimer equilibrium of reduced peroxiredoxin revealed a critical concentration in the very low micromolar range. The data suggest a cooperative assembly above this critical transition concentration where a nucleus facilitates assembly. The rather abrupt transition indicates that assembly processes do not occur below the critical transition concentration while oligomerization is efficiently triggered above it. The magnitude of the measured enthalpy confirmed the endothermic nature of the peroxiredoxin oligomerization. Heterocomplexes between peroxiredoxin polypeptides from different species were not formed. We conclude that a functional constraint conserved the dimer-decamer transition with highly similar critical transition concentrations despite emerging sequence variation during evolution.

Published 1 July 2008 in Biochemistry, 47(27): 7196-204.
Full-text of this article is available online (may require subscription).

© 2005-2008 Thermodynamics Research Today. All Rights Reserved.