Secondary structure changes of 2-Cys peroxiredoxin are associated to the formation of aggregates

FERRERO, D., ARAN, M., WOLOSIUK, A. AND WOLOSIUK, R.A.

Mar del Plata

Congreso; XLIII Reunión Nacional de la SAIB; 2007

Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular

2-Cys peroxiredoxins (2-Cys Prx) constitute a subfamily of ubiquitous peroxidases. The composition of the milieu influences the assembly of 2-Cys Prx dimers into decamers, and the latter into high molecular mass oligomers that form large filamentous oligomers in mammalian cells. Although a key to understanding the biological significance of aggregation is the characterization of the underlying mechanism, factors that drive 2-Cys Prx out of the solution are barely known. We found that the rapeseed counterpart aggregates at pH 6.0 but returns to solution either by the reversal of pH to 8 or at pHs beyond 5.5. Circular dichroism spectroscopy reveals that the aggregation was accompanied by changes in the proportion of secondary structures; b_enriched structures form at pH 6.0 while the contribution of a-helical structures increases when the pH is above 6.5 or falls below 5.5. In line with these transitions, the dynamic light scattering analysis of 2-Cys Prx uncovers that small sized oligomers build up high molecular mass species at pH 6. On the other hand, transmission electron microscopy reveals that the whole architecture is represented by globular structures of variable diameter extending for several nanometers in legth. Taking together these data indicate that the formation of b-sheet structures may be essential for the reversible formation of aggregates.