1QI9

X-RAY SIRAS STRUCTURE DETERMINATION OF A VANADIUM-DEPENDENT HALOPEROXIDASE FROM ASCOPHYLLUM NODOSUM AT 2.0 A RESOLUTION

Summary for 1QI9

• Entry DOI: 10.2210/pdb1qi9/pdb
• Descriptor: Vanadium-dependent bromoperoxidase, VANADATE ION, ... (4 entities in total)
• Functional Keywords: bromoperoxidase, vanadium, haloperoxidase, oxidoreductase
• Biological source: Ascophyllum nodosum; More
• Total number of polymer chains: 2
• Total formula weight: 121427.39

Authors

Weyand, M.,Hecht, H.-J.,Kiess, M.,Liaud, M.F.,Vilter, H.,Schomburg, D. (deposition date: 1999-06-10, release date: 2000-06-10, Last modification date: 2024-10-30)

Primary citation

Weyand, M.,Hecht, H.,Kiess, M.,Liaud, M.,Vilter, H.,Schomburg, D.
X-ray structure determination of a vanadium-dependent haloperoxidase from Ascophyllum nodosum at 2.0 A resolution.
J.Mol.Biol., 293:595-611, 1999

PubMed Abstract: 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.

PubMed: 10543953
DOI: 10.1006/jmbi.1999.3179

Experimental method

X-RAY DIFFRACTION (2.05 Å)