Uranium toxicity depends on its chemical properties rather than on its radioactivity and involves its interaction with macromolecules. Here, a systematic survey of the structural features of the uranyl sites observed in protein crystal structures deposited in the Protein Data Bank is reported. Beside the two uranyl oxygens, which occupy the axial positions, uranium tends to be coordinated by five other oxygen atoms, which occupy the equatorial vertices of a pentagonal bipyramid. Even if one or more of these equatorial positions are sometime empty, they can be occupied only by oxygen atoms that belong to the carboxylate groups of Glu and Asp side-chains, usually acting as monodentate ligands, to water molecules, or to acetate anions. Although several uranium sites appear undefined or unrefined, with a single uranium atom that lacks the two uranyl oxygen atoms, this problem seems to become less frequent in recent years. However, it is clear that the crystallographic refinements of the uranyl sites are not always well restrained and a better parametrization of these restraints seems to be necessary.

铀的毒性取决于其化学性质，而不取决于其放射性，并涉及其与大分子的相互作用。在这里，对沉积在蛋白质数据库中的蛋白质晶体结构中观察到的铀酰位点的结构特征进行了系统的调查。除了占据轴向位置的两个铀氧以外，铀还倾向于与其他五个氧原子配位，这五个氧原子占据五角双锥的赤道顶点。即使这些赤道位置中的一个或多个有时是空的，它们也只能被属于Glu和Asp侧链的羧酸根基团的氧原子占据，这些原子通常充当单齿配体，作用于水分子或作用于乙酸根阴离子。尽管有几个铀矿位未定义或未精炼，由于只有一个铀原子缺少两个铀酰氧原子，近年来，这种问题似乎变得不那么普遍了。然而，很明显，铀酰位的晶体学细化并不总是受到很好的限制，并且这些限制条件的更好的参数化似乎是必要的。