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1qi9
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(New page: 200px<br /><applet load="1qi9" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qi9, resolution 2.05Å" /> '''X-RAY SIRAS STRUCTUR...)
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Revision as of 22:36, 20 November 2007
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X-RAY SIRAS STRUCTURE DETERMINATION OF A VANADIUM-DEPENDENT HALOPEROXIDASE FROM ASCOPHYLLUM NODOSUM AT 2.0 A RESOLUTION
Overview
The homo-dimeric structure of a vanadium-dependent haloperoxidase (V-BPO), from the brown alga Ascophyllum nodosum (EC 1.1.11.X) has been solved by, single isomorphous replacement anomalous scattering (SIRAS) X-ray, crystallography at 2.0 A resolution (PDB accession code 1QI9), using two, heavy-atom datasets of a tungstate derivative measured at two different, wavelengths. The protein sequence (SwissProt entry code P81701) of V-BPO, was established by combining results from protein and DNA sequencing, and, electron density interpretation. The enzyme has nearly an all-helical, structure, with two four-helix bundles and only three small beta-sheets., The holoenzyme contains trigonal-bipyramidal coordinated vanadium atoms at, its two active centres. Structural similarity to the only other, structurally characterized vanadium-dependent chloroperoxidase (V-CPO), from Curvularia inaequalis exists in the vicinity of the active site and, to a lesser extent in the central four-helix bundle. Despite the low, sequence and structural similarity between V-BPO and V-CPO, the vanadium, binding centres are highly conserved on the N-terminal side of an, alpha-helix and include the proposed catalytic histidine residue, (His418(V-BPO)/His404(V-CPO)). The V-BPO structure contains, in addition, a second histidine near the active site (His411(V-BPO)), which can alter, the redox potential of the catalytically active VO2-O2 species by, protonation/deprotonation reactions. Specific binding sites for the, organic substrates, like indoles and monochlordimedone, or for halide ions, are not visible in the V-BPO structure. A reaction mechanism for the, enzymatic oxidation of halides is discussed, based on the present, structural, spectroscopic and biochemical knowledge of vanadium-dependent, haloperoxidases, explaining the observed enzymatic differences between, both enzymes.
About this Structure
1QI9 is a Single protein structure of sequence from Ascophyllum nodosum with VO4 and IOD as ligands. Active as Chloride peroxidase, with EC number 1.11.1.10 Full crystallographic information is available from OCA.
Reference
X-ray structure determination of a vanadium-dependent haloperoxidase from Ascophyllum nodosum at 2.0 A resolution., Weyand M, Hecht H, Kiess M, Liaud M, Vilter H, Schomburg D, J Mol Biol. 1999 Oct 29;293(3):595-611. PMID:10543953
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