Assignment of the heme axial ligand(s) for the ferric myoglobin (H93G) and heme oxygenase (H25A) cavity mutants as oxygen donors using magnetic circular dichroism.
Assignment of the heme axial ligand(s) for the ferric myoglobin (H93G) and heme oxygenase (H25A) cavity mutants as oxygen donors using magnetic circular dichroism.
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DOI：
10.1021/bi9825448
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发表时间：
1999-05
期刊：
影响因子：
2.9
通讯作者：
A. Pond;M. Roach;M. Sono;A. Rux;S. Franzen;R. B. Hu;Melissa R. Thomas;A. Wilks;Y. Dou;M. Ikeda-Saito;P. R. Montellano;W. Woodruff;S. Boxer;J. Dawson;Cle Veland
中科院分区：
文献类型：
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作者：
A. Pond;M. Roach;M. Sono;A. Rux;S. Franzen;R. B. Hu;Melissa R. Thomas;A. Wilks;Y. Dou;M. Ikeda-Saito;P. R. Montellano;W. Woodruff;S. Boxer;J. Dawson;Cle Veland
本文报道了抹香鲸H93G肌红蛋白和人H25A血红素加氧酶空腔突变体在4 ℃铁态下的紫外-可见吸收和磁性圆二色性（MCD）数据。对H93 G肌红蛋白的详细光谱分析表明，其血红素配位结构在pH 5.0时具有单个水配体，在pH 10.0时具有单个氢氧化物配体，在pH 7.0时具有多种物质的混合物，包括五配位氢氧化物结合和六配位结构。pH 5下的五配位水合结构得到了与酸性辣根过氧化物酶（pH 3.1）和酸性肌红蛋白（pH 3.4）的光谱相似性的支持，其中酸性辣根过氧化物酶（pH 3.1）的MCD数据在本文中首次报道，而酸性肌红蛋白（pH 3.4）的结构之前已通过共振拉曼光谱进行了归属。通过MCD和共振拉曼数据以及与其他已知的五配位氧供体配合物的比较，支持在pH 10.0下的五配位氢氧化物结构。特别是，碱性铁H93 G肌红蛋白的MCD谱与酪氨酸铁连接的人H93 Y肌红蛋白（本文首次报道了其MCD数据）和铁原卟啉IX二甲酯（FeIIIPPIXDME）的甲醇加合物的MCD谱惊人地相似。铁H25A血红素加氧酶在中性pH下的光谱数据分析的背景下，其他五坐标铁血红素络合物与近端氧供体配体，特别是对硝基苯酚和乙酸加合物的FeIIIPPIXDME的光谱，是最一致的连接附近的谷氨酰（或天冬氨酸）酸残基的羧酸基团。
UV-visible absorption and magnetic circular dichroism (MCD) data are reported for the cavity mutants of sperm whale H93G myoglobin and human H25A heme oxygenase in their ferric states at 4 degreesC. Detailed spectral analyses of H93G myoglobin reveal that its heme coordination structure has a single water ligand at pH 5.0, a single hydroxide ligand at pH 10.0, and a mixture of species at pH 7.0 including five-coordinate hydroxide-bound, and six-coordinate structures. The five-coordinate aquo structure at pH 5 is supported by spectral similarity to acidic horseradish peroxidase (pH 3.1), whose MCD data are reported herein for the first time, and acidic myoglobin (pH 3.4), whose structures have been previously assigned by resonance Raman spectroscopy. The five-coordinate hydroxide structure at pH 10.0 is supported by MCD and resonance Raman data obtained here and by comparison with those of other known five-coordinate oxygen donor complexes. In particular, the MCD spectrum of alkaline ferric H93G myoglobin is strikingly similar to that of ferric tyrosinate-ligated human H93Y myoglobin, whose MCD data are reported herein for the first time, and that of the methoxide adduct of ferric protoporphyrin IX dimethyl ester (FeIIIPPIXDME). Analysis of the spectral data for ferric H25A heme oxygenase at neutral pH in the context of the spectra of other five-coordinate ferric heme complexes with proximal oxygen donor ligands, in particular the p-nitrophenolate and acetate adducts of FeIIIPPIXDME, is most consistent with ligation by a carboxylate group of a nearby glutamyl (or aspartic) acid residue.