The road to the crystal structure of the cytochrome bc1 complex from the anoxigenic, photosynthetic bacterium Rhodobacter sphaeroides.
The road to the crystal structure of the cytochrome bc1 complex from the anoxigenic, photosynthetic bacterium Rhodobacter sphaeroides.
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从缺氧，光合细菌rohodobacter sphaeroides的细胞色素BC1复合物的晶体结构的道路。
DOI：
10.1007/s10863-008-9180-8
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发表时间：
2008-10
影响因子：
3
通讯作者：
Yu CA
中科院分区：
文献类型：
--
作者：
Xia D;Esser L;Elberry M;Zhou F;Yu L;Yu CA
使用细菌系统研究细胞色素 bc1 复合物的机制和功能的优势并不容易扩展到其结构研究。尽管与线粒体对应物相比，酶的尺寸更小且亚基组成更简单，但细菌复合物的高质量晶体却很难获得。在对来自球形 R. sphaeroides 的 bc1 复合物进行结构测定的过程中，我们观察到仅低质量晶体的生长与纯化复合物的低活性和稳定性相关，通过向酶引入双突变可以部分缓解这种情况。与野生型酶相比，S287R(cyt b)/V135S(ISP) 突变体的电子转移活性提高了 40%，热稳定性提高了 4.3°C。人们发现氨基酸组氨酸对于维持细菌复合物的结构完整性很重要，而呼吸抑制剂（例如豆黄素）对于铁硫蛋白外在结构域的固定是必需的。通过存在锶离子，可以进一步提高 R. sphaeroides bc1 复合体的晶体质量，产生的晶体的 X 射线衍射分辨率优于 2.3 Å。晶体质量的提高可以通过锶离子参与晶体中的分子堆积排列来理解。
The advantages of using bacterial systems to study the mechanism and function of cytochrome bc1 complexes do not extend readily to their structural investigations. High quality crystals of bacterial complexes have been difficult to obtain despite the enzymes' smaller sizes and simpler subunit compositions compared to their mitochondrial counterparts. In the course of the structure determination of the bc1 complex from R. sphaeroides, we observed that the growth of only low quality crystals correlated with low activity and stability of the purified complex, which was mitigated in part by introducing a double mutations to the enzyme. The S287R(cyt b)/V135S(ISP) mutant shows 40% increase in electron transfer activity and displays a 4.3°C increase in thermal stability over wild-type enzyme. The amino acid histidine was found important in maintaining structural integrity of the bacterial complex, while the respiratory inhibitors such as stigmatellin are required for immobilization of the iron-sulfur protein extrinsic domain. Crystal quality of the R. sphaeroides bc1 complex can be improved further by the presence of strontium ions yielding crystals that diffracted X-rays to better than 2.3 Å resolution. The improved crystal quality can be understood in terms of participation of strontium ions in molecular packing arrangement in crystal.