ATP-DEPENDENT OLIGOMERIZATION OF RAPESEED 2-CYS PEROXIREDOXIN

FERRERO D, ARAN M, WOLOSIUK RA.

Villa Carlos Paz, Córdoba

Congreso; XLIV SAIB ANNUAL MEETING; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

2-Cys peroxiredoxin (2-Cys Prx) is a subfamily of peroxidases implicated in oxidative stress and signal transduction. The covalently linked homodimers (ca. 23 kDa subunit) have a significant propensity to form non-covalently decamers (pentamer of dimers). We have shown that the rapeseed 2-Cys Prx binds ATP at a region close to the conserved “resolving” Cys175 thereby impairing the capacity to reduce hydrogen peroxide. Therefore, using surface plasmon resonance (SPR) and dynamic light scattering (DLS), we analyzed whether ATP affects the oligomerization of the protein. The dramatic increase in the SPR signal caused by the concerted action of ATP and Mg2+ (henceforth ATP/Mg) indicated the formation of large assemblies close to the sensor. Assuming a single equilibrium (ATP/Mg) + 2-Cys Prx — [(ATP/Mg)-(2-Cys Prx)], the apparent association and dissociation constants were 0.94-1 s-1 and 2.3 s-1, respectively. Congruent with this study, DLS experiments revealed that ATP/Mg converts the soluble 2-Cys Prx (diam.: 13.8 nm) to large aggregates (diam.: higher than 600 nm) which return to the original size upon the addition of EDTA. Taken together these results evince the capacity of the couple ATP/Mg for the modulation of the quaternary structure and the peroxidase activity of 2-Cys Prx and, in so doing, uncover a novel nucleotide-dependent control of the oxidative stress.