title: ATP and Mg2+ promote the reversible oligomerization and aggregation of chloroplast 2-Cys peroxiredoxin.
abstract: 2-Cys peroxiredoxins (2-Cys Prxs) are ubiquitous peroxidases with important roles in cellular antioxidant defense and hydrogen peroxide-mediated signaling. Post-translational modifications of conserved cysteines cause the transition from low to high molecular weight oligomers, triggering the functional change from peroxidase to molecular chaperone. However, it remains unclear how non-covalent interactions of 2-Cys Prx with metabolites modulate the quaternary structure. Here, we disclose that ATP and Mg(2+) (ATP/Mg) promote the self-polymerization of chloroplast 2-Cys Prx (polypeptide 23.5 kDa) into soluble higher order assemblies (>2 MDa) that proceed to insoluble aggregates beyond 5 mM ATP. Remarkably, the withdrawal of ATP or Mg(2+) brings soluble oligomers and insoluble aggregates back to the native conformation without compromising the associated functions. As confirmed by transmission electron microscopy, ATP/Mg drive the toroid-like decamers (diameter 13 nm) to the formation of large sphere-like particles (diameter ∼30 nm). Circular dichroism studies on ATP-labeled 2-Cys Prx reveal that ATP/Mg enhance the proportion of β-sheets with the concurrent decrease in the content of α-helices. In line with this observation, the formation of insoluble aggregates is strongly prevented by 2,2,2-trifluoroethanol, a cosolvent employed to induce α-helical conformations. We further find that the response of self-polymerization to ATP/Mg departs abruptly from that of the associated peroxidase and chaperone activities when two highly conserved residues, Arg(129) and Arg(152), are mutated. Collectively, our data uncover that non-covalent interactions of ATP/Mg with 2-Cys Prx modulate dynamically the quaternary structure, thereby coupling the non-redox chemistry of cell energy with redox transformations at cysteine residues.
authors.affiliation: Instituto de Investigaciones Bioquímicas-Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Depto. Química Biológica-Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina.
authors.forename: Martín
authors.initials: M
authors.lastname: Aran
authors.forename: Diego
authors.initials: D
authors.lastname: Ferrero
authors.forename: Alejandro
authors.initials: A
authors.lastname: Wolosiuk
authors.forename: Santiago
authors.initials: S
authors.lastname: Mora-García
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Wolosiuk
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics; D002942:Circular Dichroism; D008274:Magnesium / Q000737:chemistry* / Q000378:metabolism; D054464:Peroxiredoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D054464:Peroxiredoxins; D008274:Magnesium