3OJT

Structure of native Fe-containing Homoprotocatechuate 2,3-Dioxygenase at 1.70 Ang resolution

Summary for 3OJT

• Entry DOI: 10.2210/pdb3ojt/pdb
• Related: 3OJJ 3OJK 3OJN
• Descriptor: Homoprotocatechuate 2,3-dioxygenase, FE (II) ION, HEXAETHYLENE GLYCOL, ... (7 entities in total)
• Functional Keywords: oxidoreductase, dioxygenase, extradiol, metal substitution, 2his-1-carboxylate facial triad, romatic ring cleavage
• Biological source: Brevibacterium fuscum
• Total number of polymer chains: 4
• Total formula weight: 169226.66

Authors

Fielding, A.J.,Kovaleva, E.G.,Farquhar, E.R.,Lipscomb, J.D.,Que Jr., L. (deposition date: 2010-08-23, release date: 2010-12-29, Last modification date: 2023-09-06)

Primary citation

Fielding, A.J.,Kovaleva, E.G.,Farquhar, E.R.,Lipscomb, J.D.,Que, L.
A hyperactive cobalt-substituted extradiol-cleaving catechol dioxygenase.
J.Biol.Inorg.Chem., 16:341-355, 2011

PubMed Abstract: 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.

PubMed: 21153851
DOI: 10.1007/s00775-010-0732-0

Experimental method

X-RAY DIFFRACTION (1.7 Å)