Dauter Z, Wilson K S, Sieker L C, Meyer J, Moulis J M
Department of Chemistry, University of York, Heslington, York, YO1 5DD, England.
Biochemistry. 1997 Dec 23;36(51):16065-73. doi: 10.1021/bi972155y.
The crystal structure of the 2[4Fe-4S] ferredoxin from Clostridium acidurici has been solved using X-ray diffraction data extending to atomic resolution, 0.94 A, recorded at 100 K. The model was refined with anisotropic representation of atomic displacement parameters for all non-hydrogen atoms and with hydrogens riding on their parent atoms. Stereochemical restraints were applied to the protein chain but not to the iron-sulfur clusters. The final R factor is 10.03 % for all data. Inversion of the final least-squares matrix allowed direct estimation of the errors of individual parameters. The estimated errors in positions for protein main chain atoms are below 0.02 A and about 0.003 A for the heavier [4Fe-4S] cluster atoms. Significant differences between the stereochemistry of the two clusters and distortion of both of them from ideal Td tetrahedral symmetry can be defined in detail at this level of accuracy. Regions of alternative conformations include not only protein side chains but also two regions of the main chain. One such region is the loop of residues 25-29, which was highly disordered in the room temperature structure.
利用在100 K下记录的延伸至原子分辨率（0.94 Å）的X射线衍射数据，解析了来自嗜酸梭菌的2[4Fe-4S]铁氧化还原蛋白的晶体结构。对模型进行了精修，所有非氢原子的原子位移参数采用各向异性表示，氢原子置于其母体原子上。对蛋白质链施加了立体化学限制，但对铁硫簇未施加。所有数据的最终R因子为10.03%。最终最小二乘矩阵的求逆允许直接估计各个参数的误差。蛋白质主链原子位置的估计误差低于0.02 Å，较重的[4Fe-4S]簇原子的估计误差约为0.003 Å。在这个精度水平上，可以详细定义两个簇的立体化学之间的显著差异以及它们相对于理想Td四面体对称性的畸变。替代构象区域不仅包括蛋白质侧链，还包括主链的两个区域。其中一个这样的区域是25-29位残基的环，它在室温结构中高度无序。
