Kawano Y, Kumagai T, Muta K, Matoba Y, Davies J, Sugiyama M
RIKEN Harima Institute, Mikazuki-cho, Sayo, Hyogo, 679-5143, Japan.
J Mol Biol. 2000 Jan 28;295(4):915-25. doi: 10.1006/jmbi.1999.3404.
Bleomycin (Bm)-binding protein, designated BLMA, which is a Bm resistance determinant from Bm-producing Streptomyces verticillus, was crystallized in a form suitable for X-ray diffraction analysis. The diffraction intensity data were collected up to a resolution of 1.5 A with a merging R-value of 0.054 at a completeness of 94 %. The BLMA structure, determined by the single isomorphous replacement method including the anomalous scattering effect (SIR-AS) at a resolution of 2.0 A, was refined at 1.5 A resolution. The final R-factor was 19.0 % and R(free) was 22.1 % including 91 water molecules. The crystal packing showed a dimer form, which was generated by arm exchange. The 1.5 A high-resolution experiment allowed an analysis of the side-chain disorder of BLMA. The structural comparison of BLMA with a homologous protein from Streptoalloteichus hindustanus, designated Shble protein, showed that a Ser100-Gly103 loop was farther from the groove, which is a Bm-binding site, in BLMA than in the Shble protein. Furthermore the hydrophobicity of the groove in BLMA is much lower than that in the Shble protein. The structural differences between these proteins may be responsible for the observation that a half-saturating concentration (K(1/2)) of Bm is higher for BLMA than for the Shble protein.
博来霉素（Bm）结合蛋白，命名为BLMA，它是产生Bm的弗氏链霉菌的一种Bm抗性决定因素，以适合X射线衍射分析的形式结晶。收集衍射强度数据直至分辨率达到1.5 Å，合并R值为0.054，完整性为94%。通过单同晶置换法（包括反常散射效应，SIR-AS）在2.0 Å分辨率下确定的BLMA结构，在1.5 Å分辨率下进行了精修。最终R因子为19.0%，R（自由）为22.1%，包括91个水分子。晶体堆积呈二聚体形式，由臂交换产生。1.5 Å的高分辨率实验允许对BLMA的侧链无序进行分析。将BLMA与来自印度斯坦链霉菌的同源蛋白（命名为Shble蛋白）进行结构比较，结果表明，在BLMA中，Ser100-Gly103环比在Shble蛋白中离作为Bm结合位点的凹槽更远。此外，BLMA中凹槽的疏水性远低于Shble蛋白中的疏水性。这些蛋白质之间的结构差异可能是导致观察到BLMA的Bm半饱和浓度（K（1/2））高于Shble蛋白的原因。
