Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
Biochem J. 2012 Feb 1;441(3):1017-26. doi: 10.1042/BJ20111659.
The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni²⁺ ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni²⁺ insertion into the apoenzyme. Crystals of apo-HpUreE (H. pylori UreE) and its Ni⁺- and Zn⁺-bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni²⁺) and 2.52 Å (Zn²⁺) resolution, show the conserved proximal and solvent-exposed His¹⁰² residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apoprotein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His¹⁵². The analysis of X-ray absorption spectral data obtained using solutions of Ni²⁺- and Zn²⁺-bound HpUreE provided accurate information of the metal-ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal-ion binding, and the mutual influence of protein framework and metal-ion stereo-electronic properties in establishing co-ordination number and geometry leading to metal selectivity.
幽门螺杆菌病原体在胃酸性环境中的存活和生长是由脲酶的活性所保证的，脲酶是一种在活性部位含有两个必需镍离子的酶。金属伴侣蛋白 UreE 有助于在体内将 Ni²⁺插入脱辅基酶。从缺乏和存在金属离子的蛋白质溶液中获得了脱辅基-HpUreE（幽门螺杆菌 UreE）及其 Ni⁺和 Zn⁺结合形式的晶体。在 2.00 Å（脱辅基）、1.59 Å（Ni²⁺）和 2.52 Å（Zn²⁺）分辨率下测定的同源二聚体蛋白的晶体结构显示，两个相邻单体中保守的近端和溶剂暴露的 His¹⁰²残基始终参与金属结合。在晶体中，脱辅基蛋白的 C 末端区域无序，但由于 His¹⁵²的结合，在存在金属离子时会获得显著的有序性。使用 Ni²⁺和 Zn²⁺结合的 HpUreE 的溶液获得的 X 射线吸收光谱数据的分析提供了在不存在固态效应的情况下金属离子环境的准确信息。这些结果揭示了蛋白质 C 末端组氨酸残基在金属离子结合中的作用，以及蛋白质框架和金属离子立体电子性质在建立配位数和几何形状以实现金属选择性方面的相互影响。
