Catalytic Thr or Ser Residue Modulates Structural Switches in 2-Cys Peroxiredoxin by Distinct Mechanisms.

Carlos A Tairum,Marcos A De Oliveira,Ohara Augusto,Luis E S Netto,Carlos A Breyer,Melina Cardoso Santos,Stephanie Portillo-Ledesma,R Ryan Geyer,José Carlos Toledo,Marcos H Toyama,Gerardo Ferrer-Sueta,Cecilia J Nieves

doi:10.1038/srep33133

Abstract

Typical 2-Cys Peroxiredoxins (2-Cys Prxs) reduce hydroperoxides with extraordinary rates due to an active site composed of a catalytic triad, containing a peroxidatic cysteine (CP), an Arg, and a Thr (or Ser). 2-Cys Prx are involved in processes such as cancer; neurodegeneration and host-pathogen interactions. During catalysis, 2-Cys Prxs switch between decamers and dimers. Analysis of 2-Cys Prx structures in the fully folded (but not locally unfolded) form revealed a highly conserved, non-conventional hydrogen bond (CH-π) between the catalytic triad Thr of a dimer with an aromatic residue of an adjacent dimer. In contrast, structures of 2-Cys Prxs with a Ser in place of the Thr do not display this CH-π bond. Chromatographic and structural data indicate that the Thr (but not Ser) destabilizes the decamer structure in the oxidized state probably through steric hindrance. As a general trend, mutations in a yeast 2-Cys Prx (Tsa1) favoring the dimeric state also displayed a decreased catalytic activity. Remarkably, yeast naturally contains Thr-Ser variants (Tsa1 and Tsa2, respectively) with distinct oligomeric stabilities in their disulfide states.

Highlights

The reactivity of 2-Cys Prx toward peroxides is considered extraordinary as they react one to ten million times faster than free Cys[6]
Another intriguing feature of 2-Cys Prx enzymes is their ability to switch among distinct quaternary structures, which is affected by redox state, among other factors[8,9,18,19,20,21]
Since the interactions between dimers are relevant for decamer stabilization, we analyzed the structures of 2-Cys Prx enzymes available in Protein Data

Summary

Introduction

The reactivity of 2-Cys Prx toward peroxides is considered extraordinary as they react one to ten million times faster than free Cys[6]. In the FF state, CP is located in the first turn of an α-helix, surrounded by the Thr (or Ser, in some cases) and the Arg[9,10] These three residues compose the catalytic triad, which has been implicated in the reactivity and specificity of Prx towards hydroperoxides[8,9,10]. Studies involving the substitution of the conserved Thr (or Ser) residue are scarcer and show less drastic effects on catalysis[13,17] Another intriguing feature of 2-Cys Prx enzymes is their ability to switch among distinct quaternary structures, which is affected by redox state, among other factors[8,9,18,19,20,21]. Several post-translational modifications affect the stabilities of 2-Cys Prx quaternary structures, which impact their activities[26,27,28]

Methods

Results

Conclusion