8djx | pdb_00008djx

Cytosolic ascorbate peroxidase from Sorghum bicolor - Compound II

spinqualitylabelsall models 8djx, resolution 1.34Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8djx is a 1 chain structure with sequence from Sorghum bicolor. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: HEM, NA, SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function C5WNL8_SORBI Publication Abstract from PubMed In planta, H2O2 is produced as a by-product of enzymatic reactions and during defense responses. Ascorbate peroxidase (APX) is a key enzyme involved in scavenging cytotoxic H2O2. Here, we report the crystal structure of cytosolic APX from sorghum (Sorghum bicolor) (Sobic.001G410200). While the overall structure of SbAPX was similar to that of other APXs, SbAPX uniquely displayed four bound ascorbates rather than one. In addition to the É£-heme pocket identified in other APXs, ascorbates were bound at the delta-meso and two solvent-exposed pockets. Consistent with the presence of multiple binding sites, our results indicated that the H2O2-dependent oxidation of ascorbate displayed positive cooperativity. Bound ascorbate at two surface sites established an intricate proton network with ascorbate at the É£-heme edge and delta-meso sites. Based on crystal structures, steady-state kinetics and site-directed mutagenesis results, both ascorbate molecules at the É£-heme edge and the one at the surface are expected to participate in the oxidation reaction. We provide evidence that the H2O2-dependent oxidation of ascorbate by APX produces a C2-hydrated bicyclic hemiketal form of dehydroascorbic acid at the É£-heme edge, indicating two successive electron transfers from a single bound ascorbate. In addition, the delta-meso site was shared with several organic compounds, including p-coumaric acid and other phenylpropanoids, for the potential radicalization reaction. Site-directed mutagenesis of the critical residue at the É£-heme edge (R172A) only partially reduced polymerization activity. Thus, APX removes stress-generated H2O2 with ascorbates, and also uses this same H2O2 to potentially fortify cell walls via oxidative polymerization of phenylpropanoids in response to stress. A sorghum ascorbate peroxidase with four binding sites has activity against ascorbate and phenylpropanoids.,Zhang B, Lewis JA, Vermerris W, Sattler SE, Kang C Plant Physiol. 2022 Dec 28:kiac604. doi: 10.1093/plphys/kiac604. PMID:36575825 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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