The high-resolution X-ray crystal structures of the adducts formed between the “half sandwich”-type Ru(II) coordination compound [Ru^II(1,4,7-trithiacyclononane)(ethane-1,2-diamine)Cl]⁺ and two proteins, namely hen egg-white lysozyme and proteinase K, are presented. The structures unveil that upon reaction with both enzymes the Ru(II) compound is coordinated by solvent-exposed aspartate residues after releasing the chloride ligand (Asp101 in lysozyme, Asp200 and Asp260 in proteinase K), while retaining the two chelating ligands. The adduct with Asp101 residue at the catalytic cleft of lysozyme is accompanied by residue-specific conformational changes to accommodate the Ru(II) fragment, whereas the complexes bound at the two calcium-binding sites of proteinase K revealed minimal structural perturbation of the enzyme. To the best of our knowledge, proteinase K is used here for the first time as a model system of protein metalation and these are the first X-ray crystal structures of protein adducts of a Ru(II) coordination compound that maintains its coordination sphere almost intact upon binding. Our data demonstrate the role of ligands in stabilizing the protein adducts via hydrophobic/aromatic or hydrogen-bonding interactions, as well as their underlying role in the selection of specific sites on the electrostatic potential surface of the enzymes.

中文翻译：

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“半三明治”型Ru（II）配位化合物的高分辨率晶体结构与鸡蛋蛋白溶菌酶和蛋白酶K结合。

在“半夹心”型Ru（II）配位化合物[Ru ^II（1,4,7-ththiacyclononane）（乙烷-1,2-二胺）Cl]之间形成的加合物的高分辨率X射线晶体结构⁺提出了两种蛋白，即鸡蛋清溶菌酶和蛋白酶K。该结构揭示，在与两种酶反应后，Ru（II）化合物在释放氯化物配体（溶菌酶中的Asp101，蛋白酶K中的Asp200和Asp260）后，通过溶剂暴露的天冬氨酸残基进行配位，同时保留了两个螯合配体。在溶菌酶催化裂隙处带有Asp101残基的加合物伴随有残基特异性构象变化，以适应Ru（II）片段，而结合在蛋白酶K的两个钙结合位点上的复合物显示出该酶的结构扰动最小。据我们所知，此处首次将蛋白酶K用作蛋白质金属化的模型系统，这是Ru（II）的蛋白质加合物的第一个X射线晶体结构结合后几乎保持原状的协调化合物。我们的数据证明了配体在通过疏水/芳香或氢键相互作用稳定蛋白质加合物中的作用，以及它们在选择酶的静电势能表面上特定位点方面的潜在作用。