ATP Modulates the Oligomerization of Chloroplast 2-Cys Peroxiredoxin

MARTIN ARAN, DIEGO FERRERO, RICARDO WOLOSIUK

San Diego, CA, EEUU

Simposio; The 24th Annual Symposium of the Protein Society; 2010

The Protein Society

2-Cys peroxiredoxins (2-Cys Prx) are members of a large family of ubiquitous peroxidases that not only catalyze the reduction of H2O2 but also regulate cell signalling pathways, apoptosis and differentiation. All 2-Cys Prx are homodimers (α2) covalently linked via a disulfide bond that associate noncovalently in doughnut-shaped decamers (α2)5. Although mounting evidences suggest that the oxidative stress enhances formation of larger species, mechanisms of oligomerization remain largely unknown. We have recently found that ATP regulates functions of 2-Cys Prx. In the present investigation, we have examined the contribution of this nonredox modulator to the oligomerization of 2-Cys Prx. Studies of dynamic and static light scattering revealed that high concentrations of the nucleotide induces the formation of large soluble aggregates (> 2 MDa). The aggregation kinetics were studied by surface plasmon resonance yielding an apparent association equilibrium constant of 2.4 mM. We also found that the change in quaternary structure is associated with enrichment in β-sheet structures. Transmission electron microscopy images show that 2-Cys Prx assembles into decamers in the absence of perturbants but turns to spherical particles in the presence of ATP. Hence, this non-redox structural modulation can explain the previously observed ATP-mediated regulation of 2-Cys Prx and concurrently suggest that, in addition to its functions in the detoxification of peroxides, the oligomerization may be the underlying mechanism for sensing the energy status of chloroplasts.