X-ray structure determination of a vanadium-dependent haloperoxidase from Ascophyllum nodosum at 2.0 Ã… resolution
X-ray structure determination of a vanadium-dependent haloperoxidase from Ascophyllum nodosum at 2.0 Ã… resolution
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DOI：
10.1006/jmbi.1999.3179
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发表时间：
1999-10-29
影响因子：
5.6
通讯作者：
Schomburg, D
中科院分区：
文献类型：
--
作者：
Weyand, M;Hecht, HJ;Schomburg, D
用2.0埃分辨率(PDB加入码1QI9)的单次同象置换反常散射(SIRAS)X射线单晶衍射法，用两个不同波长下测量的钨酸盐衍生物的重原子数据，解决了褐藻结节阿司匹林(EC 1.1.11.X)中依赖钒的卤代过氧化物酶(V-BPO)的同二聚体结构。结合蛋白质和DNA测序结果以及电子密度解析，建立了V-BPO的蛋白质序列(SwissProt Entry Codes P81701)。这种酶几乎是全螺旋结构，有两个四螺旋束，只有三个小的β-折叠。全酶的两个活性中心都含有三方双锥配位的钒原子。尽管V-BPO和V-CPO的序列和结构上的相似性较低，但钒结合中心在α-螺旋的N端是高度保守的，并且包括所提出的催化组氨酸残基(His418(V-BPO)/His(V-CPO))。此外，V-BPO结构在活性中心附近还含有第二个组氨酸(His411(V-BPO))，它可以通过质子化/去质子化反应改变催化活性的VO2-O-2物种的氧化还原电位。在V-BPO结构中看不到有机底物(如吲哚和一氯二酮)或卤化物离子的特定结合部位。根据目前依赖钒的卤代过氧化物酶的结构、光谱和生化知识，讨论了卤化物的酶促氧化反应机理，解释了观察到的两种酶之间的酶促差异。(C)1999年学术出版社。
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 Angstrom 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)/His(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-O-2 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. (C) 1999 Academic Press.