4z6p

Structure of H200Q variant of Homoprotocatechuate 2,3-Dioxygenase from B.fuscum in complex with HPCA at 1.75 Ang resolution

spinqualitylabelsall models 4z6p, resolution 1.75Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4z6p 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 1.75Å Ligands: CL, DHY, FE2, P6G, PG4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q45135_9MICO Publication Abstract from PubMed Kinetic and spectroscopic studies have shown that the conserved active site residue His200 of the extradiol ring-cleaving homoprotocatechuate 2,3-dioxygenase (FeHPCD) from Brevibacterium fuscum is critical for efficient catalysis. The roles played by this residue are probed here by analysis of the steady-state kinetics, pH dependence, and X-ray crystal structures of the FeHPCD position 200 variants His200Asn, His200Gln, and His200Glu alone and in complex with three catecholic substrates (homoprotocatechuate, 4-sulfonylcatechol, and 4-nitrocatechol) possessing substituents with different inductive capacity. Structures determined at 1.35-1.75 A resolution show that there is essentially no change in overall active site architecture or substrate binding mode for these variants when compared to the structures of the wild-type enzyme and its analogous complexes. This shows that the maximal 50-fold decrease in kcat for ring cleavage, the dramatic changes in pH dependence, and the switch from ring cleavage to ring oxidation of 4-nitrocatechol by the FeHPCD variants can be attributed specifically to the properties of the altered second-sphere residue and the substrate. The results suggest that proton transfer is necessary for catalysis, and that it occurs most efficiently when the substrate provides the proton and His200 serves as a catalyst. However, in the absence of an available substrate proton, a defined proton-transfer pathway in the protein can be utilized. Changes in the steric bulk and charge of the residue at position 200 appear to be capable of altering the rate-limiting step in catalysis and, perhaps, the nature of the reactive species. Structural Basis for Substrate and Oxygen Activation in Homoprotocatechuate 2,3-Dioxygenase: Roles of Conserved Active Site Histidine 200.,Kovaleva EG, Rogers MS, Lipscomb JD Biochemistry. 2015 Aug 19. PMID:26267790 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Dioxygenase 3D structures

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