Summary for 3Q09
| Entry DOI | 10.2210/pdb3q09/pdb |
| Related | 3Q08 |
| Descriptor | Chlorite dismutase, PROTOPORPHYRIN IX CONTAINING FE, NITRITE ION, ... (5 entities in total) |
| Functional Keywords | ferrodoxin fold, chlorite decomposition, o2 generation, periplasim, oxidoreductase |
| Biological source | Dechloromonas aromatica |
| Cellular location | Periplasm : Q47CX0 |
| Total number of polymer chains | 20 |
| Total formula weight | 577637.68 |
| Authors | Goblirsch, B.R.,Wilmot, C.M. (deposition date: 2010-12-15, release date: 2011-01-05, Last modification date: 2024-02-21) |
| Primary citation | Goblirsch, B.R.,Streit, B.R.,DuBois, J.L.,Wilmot, C.M. Structural features promoting dioxygen production by Dechloromonas aromatica chlorite dismutase. J.Biol.Inorg.Chem., 15:879-888, 2010 Cited by PubMed Abstract: Chlorite dismutase (Cld) is a heme enzyme capable of rapidly and selectively decomposing chlorite (ClO(2) (-)) to Cl(-) and O(2). The ability of Cld to promote O(2) formation from ClO(2) (-) is unusual. Heme enzymes generally utilize ClO(2) (-) as an oxidant for reactions such as oxygen atom transfer to, or halogenation of, a second substrate. The X-ray crystal structure of Dechloromonas aromatica Cld co-crystallized with the substrate analogue nitrite (NO(2) (-)) was determined to investigate features responsible for this novel reactivity. The enzyme active site contains a single b-type heme coordinated by a proximal histidine residue. Structural analysis identified a glutamate residue hydrogen-bonded to the heme proximal histidine that may stabilize reactive heme species. A solvent-exposed arginine residue likely gates substrate entry to a tightly confined distal pocket. On the basis of the proposed mechanism of Cld, initial reaction of ClO(2) (-) within the distal pocket generates hypochlorite (ClO(-)) and a compound I intermediate. The sterically restrictive distal pocket probably facilitates the rapid rebound of ClO(-) with compound I forming the Cl(-) and O(2) products. Common to other heme enzymes, Cld is inactivated after a finite number of turnovers, potentially via the observed formation of an off-pathway tryptophanyl radical species through electron migration to compound I. Three tryptophan residues of Cld have been identified as candidates for this off-pathway radical. Finally, a juxtaposition of hydrophobic residues between the distal pocket and the enzyme surface suggests O(2) may have a preferential direction for exiting the active site. PubMed: 20386942DOI: 10.1007/s00775-010-0651-0 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (3 Å) |
Structure validation
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