Durley R C, Mathews F S
Department of Biochemistry and Molecular Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Acta Crystallogr D Biol Crystallogr. 1996 Jan 1;52(Pt 1):65-76. doi: 10.1107/S0907444995007827.
The structure of bovine liver cytochrome b(5), a soluble 93-residue proteolytic fragment of a 16 kDa membrane-bound hemoprotein, initially solved at 2.0 A resolution, has been refined at 1.5 A using data collected on a diffractometer. Refinement to 2.0 A resolution used the Hendrickson-Konnert procedure PROLSQ and was then extended to 1.5 A resolution using the program PROFFT. Only residues 3-87 could be identified in the model and these residues together with 93 water molecules gave an agreement factor of R = 0.161 for data in the resolution range 1.5-5 A. The structure was finally refined using the program X-PLOR, which enabled alternate conformers to be modelled for several surface side chains. Residues 1 and 2 at the amino terminus of the protein and residue 88 near the carboxyl terminus could be identified from these electron-density maps. However the remaining disordered carboxy-terminal residues could not successfully be included in the model. A total of 117 solvent molecules were included in the final refinement to give R = 0.164 for the data between 1.5 and 10 A.
牛肝细胞色素b(5)是一种16 kDa膜结合血红蛋白的可溶性93个残基的蛋白水解片段，其结构最初在2.0 Å分辨率下解析，现使用在衍射仪上收集的数据在1.5 Å分辨率下进行了精修。在2.0 Å分辨率下的精修使用了Hendrickson-Konnert程序PROLSQ，然后使用PROFFT程序扩展到1.5 Å分辨率。模型中仅能识别出3 - 87位残基，这些残基与93个水分子一起，对于1.5 - 5 Å分辨率范围内的数据，给出了R = 0.161的吻合因子。最终使用X-PLOR程序对结构进行精修，该程序能够为几个表面侧链构建交替构象。从这些电子密度图中可以识别出蛋白质氨基末端的1和2位残基以及羧基末端附近的88位残基。然而，其余无序的羧基末端残基未能成功纳入模型。最终精修中总共纳入了117个溶剂分子，对于1.5至10 Å之间的数据，R = 0.164。
