Emerging role of rare earth elements in biomolecular functions.

The importance of rare earth elements is increasingly recognized due to the increased demand for their mining and separation. This demand is driving research on the biology of rare earth elements. Biomolecules associated with rare earth elements include rare earth element-dependent enzymes (methanol dehydrogenase XoxF, ethanol dehydrogenase ExaF/PedH), rare earth element-binding proteins, and the relevant metallophores. Traditional (chemical) separation methods for rare earth elements harvesting and separation are typically inefficient, while causing environmental problems, whereas bioharvesting, potentially, offers more efficient, more green platforms. Here, we review the current state of research on the biological functions of rare earth element-dependent biomolecules, and the characteristics of the relevant proteins, including the specific amino acids involved in rare earth metal binding. We also provide an outlook at strategies for further understanding of biological processes and the potential applications of rare earth element-dependent enzymes and other biomolecules.