How active-site protonation state influences the reactivity and ligation of the heme in chlorite dismutase.
How active-site protonation state influences the reactivity and ligation of the heme in chlorite dismutase.
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DOI：
10.1021/ja9082182
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发表时间：
2010-04-28
影响因子：
15
通讯作者：
DuBois, Jennifer L.
中科院分区：
文献类型：
--
作者：
Streit, Bennett R.;Blanc, Beatrice;Lukat-Rodgers, Gudrun S.;Rodgers, Kenton R.;DuBois, Jennifer L.
亚氯酸盐歧化酶催化亚氯酸盐释放O2，具有极高的效率和特异性。研究了芳香十氯单胞菌亚氯酸盐歧化酶在pH 3~11.5范围内的光谱性质、配体结合亲和力和稳态动力学，以了解血红素环境的质子化状态如何影响氧气的生成。用紫外可见光谱和共振拉曼光谱观察到酸/碱转变，pKa为8.7，2-3个pH单位低于典型的组氨酸连接的过氧化物酶的类似转变。共振拉曼光谱证实，这一转变标志着五配位的高自旋Fe(III)转变为高/低自旋的混合氢氧化铁。尽管近端组氨酸配体的咪唑侧链近中性，但两个Fe-OH伸缩频率相当低，与弱的Fe-OH键一致。氢氧化物被认为与远端的氢键给体发生强烈的相互作用，从而削弱了Fe-OH键。Cd-CO的RR谱随pH的变化显示了两种形式的络合物，一种是远端残基与羰基氧相互作用最少的形式，另一种是氧受正电荷影响的酸性形式。最近的结晶学数据显示，精氨酸183是末端口袋中唯一的氢键供体残基。振动数据表明，该Arg很可能是一个强的、带正电荷的氢键供体，与外源的轴向血红素配体相互作用。中性形式(pKa~6.5)的Arg在质子化配体(如HCN)与三氯化铁的结合反应中也起到了活性中心碱的作用。用这些相同的pKa表征了绿泥石分解速率的稳态分布。5配位的高自旋酸性Cld比碱性氢氧化物结合形式更具活性。当末端的Arg被质子化/阳离子(最大kcat=2.0(±0.6)×10 5 S−1，kcat/Km=3.2(±0.4)×10 7M−1s−1，pH 5.2，4°C)时，绿泥石的分解最有效，而在碱性条件下，当它作为轴向氢氧化物配体的氢键供体时，绿泥石的分解程度较小。
Chlorite dismutase catalyzes O2 release from chlorite with exquisite efficiency and specificity. The spectroscopic properties, ligand binding affinities, and steady state kinetics of chlorite dismutase from Dechloromonas aromatica were examined over pH 3–11.5 to gain insight into how the protonation state of the heme environment influences dioxygen formation. An acid/base transition was observed by UV/visible and resonance Raman spectroscopy with a pKa of 8.7, 2–3 pH units below analogous transitions observed in typical His-ligated peroxidases. This transition marks the conversion of a five coordinate high spin Fe(III) to a mixed high/low spin ferric-hydroxide, as confirmed by resonance Raman (rR) spectroscopy. The two Fe–OH stretching frequencies are quite low, consistent with a weak Fe–OH bond, despite the nearly neutral imidazole side chain of the proximal histidine ligand. The hydroxide is proposed to interact strongly with a distal H-bond donor, thereby weakening the Fe–OH bond. The rR spectra of Cld-CO as a function of pH reveal two forms of the complex, one in which there is minimal interaction of distal residues with the carbonyl oxygen and another, acidic form in which the oxygen is under the influence of positive charge. Recent crystallographic data reveal arginine 183 as the lone H-bond donating residue in the distal pocket. It is likely that this Arg is the strong, positively charged H-bond donor implicated by vibrational data to interact with exogenous axial heme ligands. The same Arg in its neutral (pKa ~ 6.5) form also appears to act as the active site base in binding reactions of protonated ligands, such as HCN, to ferric Cld. The steady state profile for the rate of chlorite decomposition is characterized by these same pKas. The 5 coordinate high spin acidic Cld is more active than the alkaline hydroxide-bound form. The acid form decomposes chlorite most efficiently when the distal Arg is protonated/cationic (maximum kcat = 2.0 (±0.6) × 105 s−1, kcat/KM = 3.2 (±0.4) × 107 M−1s−1, pH 5.2, 4 °C) and to a somewhat lesser extent when it acts as a H-bond donor to the axial hydroxide ligand under alkaline conditions.
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影响因子：
2.9
作者：
Dou, Y;Olson, JS;IkedaSaito, M
通讯作者：
IkedaSaito, M
影响因子：
2.9
作者：
Bidwai, A;Witt, M;Erman, JE
通讯作者：
Erman, JE
影响因子：
2.9
作者：
ASHER, SA;VICKERY, LE;SAUER, K
通讯作者：
SAUER, K
DOI：
10.1039/d3ta00655g
发表时间：
--
期刊：
Journal of Materials Chemistry A
影响因子：
9.5
作者：
Zhongheng Wang; Hui Xu; Zhiruo Liu; Mingzhe Jin; Linghao Deng; Sa Li; Yunhui Huang
通讯作者：
Zhongheng Wang
影响因子：
2.9
作者：
BERRY, EA;TRUMPOWER, BL
通讯作者：
TRUMPOWER, BL