Refinement and structural analysis of barnase at 1.5 Å resolution
Refinement and structural analysis of barnase at 1.5 Å resolution
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DOI：
10.1107/s0907444998010865
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发表时间：
1999-02-01
影响因子：
2.2
通讯作者：
Mauguen, Y
中科院分区：
文献类型：
--
作者：
Martin, C;Richard, V;Mauguen, Y
淀粉液化芽孢杆菌核糖核酸酶(Barnase)是一种胞外110个残基的酶，最初以2.0埃的分辨率解析，已使用同步辐射和成像板扫描仪在1.5埃的分辨率下进行了精炼。各向异性原子位移参数的改进提高了结构的精确度。最终模型的结晶学R因子为11.5%，无R因子为17.4%。不对称单元中的三个独立分子，称为A、B和C，允许详细分析这一最终模型，并与与核苷酸抑制剂或其天然细胞内抑制剂Barstar形成络合物的Barnase的结构进行有意义的比较，对整个溶剂结构的分析显示，每个Barnase分子都有类似数量的水分子；其中有16个等价的埋藏的溶剂分子，详细讨论了它们的位置，并根据它们的结构作用进行了分类。文中还强调了水分子对棒状物-棒状物相互作用的重要作用。目前分析的高精确度揭示了锌离子的存在，它调解了一对对称性相关的A、B或C分子之间的接触：以前只在一对C分子中发现了这样的离子。
The structure of Bacillus amyloliquefaciens ribonuclease (barnase), an extracellular 110-residue enzyme initially solved at 2.0 Angstrom resolution, has been refined at 1.5 Angstrom using synchrotron radiation and an imaging-plate scanner. Refinement with anisotropic atomic displacement parameters resulted in increased accuracy of the structure. The final model has a crystallographic R factor of 11.5% and an R-free of 17.4%. The three independent molecules in the asymmetric unit, referred to as A, B and C, allowed detailed analysis of this final model and meaningful comparison with structures of barnase complexed either with nucleotide inhibitors or with its natural intracellular inhibitor, barstar, The analysis of the overall solvent structure revealed a similar number of water molecules associated with each barnase molecule; among these were 16 equivalent buried solvent molecules, the locations of which are discussed in detail and classified on the basis of their structural role. The importance of the water molecules' contribution to the barnase-barstar interaction is also highlighted. The high accuracy of the present analysis revealed the presence of a Zn2+ ion mediating the contacts between pairs of symmetry-related A, B or C molecules: such an ion had previously only been identified for pairs of C molecules.