Transferrin, the Fe(III) transport protein in mammalian blood, has been suggested to also serve as a Cr(III) transporter and as part of a Cr(III) detoxification system; however, the structure of the metal-binding sites has never been fully elucidated with bound Cr(III). Chromium(III)-transferrin was crystallized in the presence of the synergistic anion malonate. In the crystals, the protein exists with a closed C-terminal lobe containing a Cr(III) ion and an open, unoccupied N-terminal lobe. The overall structure and the metal ion environments are extremely similar to those of Fe(III)- and Ti(IV)-containing transferrin crystallized under comparable conditions. The octahedral coordination about the Cr(III) is comprised of four ligands provided by the protein (two tyrosine residues, a histidine residue, and an aspartate residue) and a chelating malonate anion. This represents the first crystal structure of a Cr(III)-containing protein that binds Cr(III) as part of its physiological function.

转铁蛋白，即哺乳动物血液中的Fe（III）转运蛋白，已被认为也可以作为Cr（III）转运蛋白和Cr（III）解毒系统的一部分。然而，从未用结合的Cr（III）完全阐明金属结合位点的结构。铬（III）-转铁蛋白在协同阴离子丙二酸酯存在下结晶。在晶体中，蛋白质存在着一个封闭的C端叶，其中含有一个Cr（III）离子，一个空的，未占据的N端叶。总体结构和金属离子环境与在可比较条件下结晶的含Fe（III）和Ti（IV）的转铁蛋白极为相似。Cr（III）的八面体配位由蛋白质提供的四个配体组成（两个酪氨酸残基，一个组氨酸残基，和天冬氨酸残基）和螯合丙二酸根阴离子。这代表了含有Cr（III）的蛋白质的第一晶体结构，该蛋白质结合Cr（III）作为其生理功能的一部分。