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Structural basis for the modulation of plant cytosolic triosephosphate isomerase activity by mimicry of redox‐based modifications
Author(s) -
CastroTorres Eduardo,
JiménezSandoval Pedro,
RomeroRomero Sergio,
FuentesPascacio Alma,
LópezCastillo Laura M.,
DíazQuezada Corina,
FernándezVelasco D. Alejandro,
TorresLarios Alfredo,
Brieba Luis G.
Publication year - 2019
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.14375
Subject(s) - cysteine , biochemistry , chemistry , triosephosphate isomerase , active site , dimer , amino acid , serine , oxidative phosphorylation , residue (chemistry) , cytosol , enzyme , stereochemistry , organic chemistry
Summary Reactive oxidative species ( ROS ) and S‐ glutathionylation modulate the activity of plant cytosolic triosephosphate isomerases ( cTPI ). Arabidopsis thaliana cTPI (Atc TPI ) is subject of redox regulation at two reactive cysteines that function as thiol switches. Here we investigate the role of these residues, Atc TPI ‐Cys13 and At‐Cys218, by substituting them with aspartic acid that mimics the irreversible oxidation of cysteine to sulfinic acid and with amino acids that mimic thiol conjugation. Crystallographic studies show that mimicking Atc TPI ‐Cys13 oxidation promotes the formation of inactive monomers by reposition residue Phe75 of the neighboring subunit, into a conformation that destabilizes the dimer interface. Mutations in residue Atc TPI ‐Cys218 to Asp, Lys, or Tyr generate TPI variants with a decreased enzymatic activity by creating structural modifications in two loops (loop 7 and loop 6) whose integrity is necessary to assemble the active site. In contrast with mutations in residue Atc TPI ‐Cys13, mutations in Atc TPI ‐Cys218 do not alter the dimeric nature of Atc TPI . Therefore, modifications of residues Atc TPI ‐Cys13 and Atc TPI ‐Cys218 modulate Atc TPI activity by inducing the formation of inactive monomers and by altering the active site of the dimeric enzyme, respectively. The identity of residue Atc TPI ‐Cys218 is conserved in the majority of plant cytosolic TPI s, this conservation and its solvent‐exposed localization make it the most probable target for TPI regulation upon oxidative damage by reactive oxygen species. Our data reveal the structural mechanisms by which S ‐glutathionylation protects Atc TPI from irreversible chemical modifications and re‐routes carbon metabolism to the pentose phosphate pathway to decrease oxidative stress.