Crystallographic and spectroscopic studies of peroxide-derived myoglobin compound II and occurrence of protonated FeIV-O
Crystallographic and spectroscopic studies of peroxide-derived myoglobin compound II and occurrence of protonated FeIV-O
复制标题
DOI：
10.1074/jbc.m701948200
复制
发表时间：
2007-08-10
影响因子：
4.8
通讯作者：
Andersson, K. Kristoffer
中科院分区：
文献类型：
--
作者：
Hersleth, Hans-Petter;Uchida, Takeshi;Andersson, K. Kristoffer
肌红蛋白在pH 5.2-8.7范围内的高分辨晶体结构已被用作血红素过氧化物酶和加氧酶中过氧化氢衍生化合物II中间体的模型。观察到的Fe-O键长(1.86-1.90埃)与单键长度一致。用单晶显微分光光度法控制同步加速器数据采集前后晶体中肌红蛋白的化合物II状态。我们观察到辐射诱导的化合物II(产生中间态H)和肌红蛋白的静息铁态的一些变化。这些辐射诱导的状态是非常不稳定的，化合物II和铁肌红蛋白立即通过在晶体的玻璃化转变温度(<；1 S)以上的短暂加热而再生。与未受影响的化合物II相比，这对我们的化合物II的结构有何影响尚不清楚，但一些结晶学数据表明，这对Fe-O键距离的影响很小。根据我们的结晶学和光谱数据，我们认为对于肌红蛋白，化合物II的中间体由具有单键的Fe-IV-O物种组成。穆斯堡尔谱的差值为0.07 mm/S，表明Fe-IV的存在。早期的量子精化(分子力学势能被量子化学计算取代的晶体精化)和密度泛函理论计算表明，这种中间H物种是质子化的。
High resolution crystal structures of myoglobin in the pH range 5.2-8.7 have been used as models for the peroxide-derived compound II intermediates in heme peroxidases and oxygenases. The observed Fe-O bond length (1.86-1.90 angstrom) is consistent with that of a single bond. The compound II state of myoglobin in crystals was controlled by single-crystal microspectrophotometry before and after synchrotron data collection. We observe some radiation-induced changes in both compound II (resulting in intermediate H) and in the resting ferric state of myoglobin. These radiation-induced states are quite unstable, and compound II and ferric myoglobin are immediately regenerated through a short heating above the glass transition temperature (< 1 s) of the crystals. It is unclear how this influences our compound II structures compared with the unaffected compound II, but some crystallographic data suggest that the influence on the Fe-O bond distance is minimal. Based on our crystallographic and spectroscopic data we suggest that for myoglobin the compound II intermediate consists of an Fe-IV-O species with a single bond. The presence of Fe-IV is indicated by a small isomer shift of delta = 0.07 mm/s from Mossbauer spectroscopy. Earlier quantum refinements (crystallographic refinement where the molecular-mechanics potential is replaced by a quantum chemical calculation) and density functional theory calculations suggest that this intermediate H species is protonated.