A repertoire of transporters plays a crucial role in maintaining homeostasis of biologically essential transition metals, manganese, and iron, thus ensuring cell viability. Elucidating the structure and function of many of these transporters has provided substantial understanding into how these proteins help maintain the optimal cellular concentrations of these metals. In particular, recent high-resolution structures of several transporters bound to different metals enable an examination of how the coordination chemistry of metal ion–protein complexes can help us understand metal selectivity and specificity. In this review, we first provide a comprehensive list of both specific and broad-based transporters that contribute to cellular homeostasis of manganese (Mn2+) and iron (Fe2+ and Fe3+) in bacteria, plants, fungi, and animals. Furthermore, we explore the metal-binding sites of the available high-resolution metal-bound transporter structures (Nramps, ABC transporters, P-type ATPase) and provide a detailed analysis of their coordination spheres (ligands, bond lengths, bond angles, and overall geometry and coordination number). Combining this information with the measured binding affinity of the transporters towards different metals sheds light into the molecular basis of substrate selectivity and transport. Moreover, comparison of the transporters with some metal scavenging and storage proteins, which bind metal with high affinity, reveal how the coordination geometry and affinity trends reflect the biological role of individual proteins involved in the homeostasis of these essential transition metals.
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Phagocytosis involves the engulfment and digestion of detrimental foreign objects (e.g., microbes) by different immune cells of our body, such as macrophages. Lipids play an important role during this immunological process, and hence, microbes have found ways to hijack these lipid pathways during phagocytosis to evade the immune system. For further information, see the review in this issue by Saharan and Kamat, pages 1279–1287. Image provided by Siddhesh Shashikant Kamat.
Structures and coordination chemistry of transporters involved in manganese and iron homeostasis
Shamayeeta Ray, Rachelle Gaudet; Structures and coordination chemistry of transporters involved in manganese and iron homeostasis. Biochem Soc Trans 28 June 2023; 51 (3): 897–923. doi: https://doi.org/10.1042/BST20210699
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