3ojk | pdb_00003ojk

Structure of Co-substituted Homoprotocatechuate 2,3-Dioxygenase in complex with 4-nitrocatechol at 1.68 Ang resolution

spinqualitylabelsall models 3ojk, resolution 1.68Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3ojk is a 4 chain structure with sequence from Brevibacterium fuscum. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.68Å Ligands: 4NC, CA, CL, CO, P6G, PG4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q45135_9MICO Publication Abstract from PubMed Homoprotocatechuate 2,3-dioxygenase from Brevibacterium fuscum (HPCD) has an Fe(II) center in its active site that can be replaced with Mn(II) or Co(II). Whereas Mn-HPCD exhibits steady-state kinetic parameters comparable to those of Fe-HPCD, Co-HPCD behaves somewhat differently, exhibiting significantly higher [Formula: see text] and k (cat). The high activity of Co-HPCD is surprising, given that cobalt has the highest standard M(III/II) redox potential of the three metals. Comparison of the X-ray crystal structures of the resting and substrate-bound forms of Fe-HPCD, Mn-HPCD, and Co-HPCD shows that metal substitution has no effect on the local ligand environment, the conformational integrity of the active site, or the overall protein structure, suggesting that the protein structure does not differentially tune the potential of the metal center. Analysis of the steady-state kinetics of Co-HPCD suggests that the Co(II) center alters the relative rate constants for the interconversion of intermediates in the catalytic cycle but still allows the dioxygenase reaction to proceed efficiently. When compared with the kinetic data for Fe-HPCD and Mn-HPCD, these results show that dioxygenase catalysis can proceed at high rates over a wide range of metal redox potentials. This is consistent with the proposed mechanism in which the metal mediates electron transfer between the catechol substrate and O(2) to form the postulated [M(II)(semiquinone)superoxo] reactive species. These kinetic differences and the spectroscopic properties of Co-HPCD provide new tools with which to explore the unique O(2) activation mechanism associated with the extradiol dioxygenase family. A hyperactive cobalt-substituted extradiol-cleaving catechol dioxygenase.,Fielding AJ, Kovaleva EG, Farquhar ER, Lipscomb JD, Que L Jr J Biol Inorg Chem. 2010 Dec 14. PMID:21153851 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Dioxygenase 3D structures

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