TY - JOUR
T1 - Structural analysis of peroxide-soaked MnSOD crystals reveals side-on binding of peroxide to active-site manganese
AU - Porta, Jason
AU - Vahedi-Faridi, Ardeschir
AU - Borgstahl, Gloria E.O.
N1 - Funding Information:
The authors would like to thank David Silverman for helpful and insightful discussion. This work was supported by NASA grants NAG-1380 and NAG8-1825 .
PY - 2010/6
Y1 - 2010/6
N2 - The superoxide dismutase (SOD) enzymes are important antioxidant agents that protect cells from reactive oxygen species. The SOD family is responsible for catalyzing the disproportionation of superoxide radical to oxygen and hydrogen peroxide. Manganese- and iron-containing SOD exhibit product inhibition whereas Cu/ZnSOD does not. Here, we report the crystal structure of Escherichia coli MnSOD with hydrogen peroxide cryotrapped in the active site. Crystallographic refinement to 1.55 Å and close inspection revealed electron density for hydrogen peroxide in three of the four active sites in the asymmetric unit. The hydrogen peroxide molecules are in the position opposite His26 that is normally assumed by water in the trigonal bipyramidal resting state of the enzyme. Hydrogen peroxide is present in active sites B, C, and D and is side-on coordinated to the active-site manganese. In chains B and D, the peroxide is oriented in the plane formed by manganese and ligands Asp167 and His26. In chain C, the peroxide is bound, making a 70° angle to the plane. Comparison of the peroxide-bound active site with the hydroxide-bound octahedral form shows a shifting of residue Tyr34 towards the active site when peroxide is bound. Comparison with peroxide-soaked Cu/ZnSOD indicates end-on binding of peroxide when the SOD does not exhibit inhibition by peroxide and side-on binding of peroxide in the product-inhibited state of MnSOD.
AB - The superoxide dismutase (SOD) enzymes are important antioxidant agents that protect cells from reactive oxygen species. The SOD family is responsible for catalyzing the disproportionation of superoxide radical to oxygen and hydrogen peroxide. Manganese- and iron-containing SOD exhibit product inhibition whereas Cu/ZnSOD does not. Here, we report the crystal structure of Escherichia coli MnSOD with hydrogen peroxide cryotrapped in the active site. Crystallographic refinement to 1.55 Å and close inspection revealed electron density for hydrogen peroxide in three of the four active sites in the asymmetric unit. The hydrogen peroxide molecules are in the position opposite His26 that is normally assumed by water in the trigonal bipyramidal resting state of the enzyme. Hydrogen peroxide is present in active sites B, C, and D and is side-on coordinated to the active-site manganese. In chains B and D, the peroxide is oriented in the plane formed by manganese and ligands Asp167 and His26. In chain C, the peroxide is bound, making a 70° angle to the plane. Comparison of the peroxide-bound active site with the hydroxide-bound octahedral form shows a shifting of residue Tyr34 towards the active site when peroxide is bound. Comparison with peroxide-soaked Cu/ZnSOD indicates end-on binding of peroxide when the SOD does not exhibit inhibition by peroxide and side-on binding of peroxide in the product-inhibited state of MnSOD.
KW - Hydrogen peroxide
KW - Manganese superoxide dismutase
KW - Product inhibition
KW - Side-on binding
KW - X-ray crystallography
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U2 - 10.1016/j.jmb.2010.04.031
DO - 10.1016/j.jmb.2010.04.031
M3 - Article
C2 - 20417642
AN - SCOPUS:77954758267
SN - 0022-2836
VL - 399
SP - 377
EP - 384
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 3
ER -