Crystal Structure and Spectroscopic Studies of a Stable Mixed-Valent State of the Hemerythrin-like Domain of a Bacterial Chemotaxis Protein
Crystal Structure and Spectroscopic Studies of a Stable Mixed-Valent State of the Hemerythrin-like Domain of a Bacterial Chemotaxis Protein
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DOI：
10.1021/ic2001267
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发表时间：
2011-06-06
影响因子：
4.6
通讯作者：
Hayashi, Takashi
中科院分区：
文献类型：
--
作者：
Onoda, Akira;Okamoto, Yasunori;Hayashi, Takashi
脱硫弧菌DcrH（Desulfovibrio vulgaris DcrH-Hr）的细菌趋化蛋白是一种O-2敏感蛋白。这种蛋白质有一个hemerythrin样结构域，其中包括一个非血红素二铁中心类似于hemerythrin（Hr）家族的二铁中心。有趣的是，DcrH-Hr的O-2亲和力为3.3 × 10（6）M-1，比果胶菌Hr的O-2亲和力高25倍。这种高亲和力来自O-2配体与DcrH-Hr的快速缔合（k（on）= 5.3 × 10（8）M-1 s（-1）），这是通过加速O-2配体通过二铁位点的疏水通道而实现的。此外，自氧化动力学表明，DcrH-Hr的自氧化速率比P. gouldii Hr的自氧化速率高54倍，表明DcrH-Hr的氧化形式对于自氧化不稳定。更重要的是，在以前的Hr研究中通过光谱观察到的混合价态，半金属（R），semimet（R）-（1.8埃）和met-DcrH-Hr（1.4埃）的高分辨率晶体结构表明，semimet（R）-和met-DcrH-Hr物质在二铁位点具有非常相似的配位几何形状。
The bacterial chemotaxis protein of Desulfovibrio vulgaris DcrH (DcrH-Hr) functions as an O-2-sensing protein. This protein has a hemerythrin-like domain that includes a nonheme diiron center analogous to the diiron center of the hemerythrin (Hr) family. Interestingly, the O-2 affinity of DcrH-Hr is 3.3 x 10(6) M-1, a value 25-fold higher than that of the Pectinaria gouldii Hr. This high affinity arises from the fast association of the O-2 ligand with DcrH-Hr (k(on) = 5.3 x 10(8) M-1 s(-1)), which is made possible by a hydrophobic tunnel that accelerates the passage of the O-2 ligand to the diiron site. Furthermore, the autoxidation kinetics indicate that the rate of autoxidation of DcrH-Hr is 54-fold higher than that of P. gouldii Hr, indicating that the oxy form of DcrH-Hr is not stable toward autoxidation. More importantly, a mixed-valent state, semimet(R), which was spectroscopically observed in previous Hr studies, was found to be stable for over 1 week and isolable in the case of DcrH-Hr. The high-resolution crystal structures of the semimet(R)- (1.8 angstrom) and met-DcrH-Hr (1.4 angstrom) indicate that the semimetR- and met-DcrH-Hr species have very similar coordination geometry at the diiron site.