Structural insights into the selectivity of lanthanide-binding peptides and proteins

Lanthanide(Ln)-binding peptides and proteins, such as lanthanide-binding tags (LBT) and Lanmodulin (LanM), are the focus of intensive research owing to (i) their applications in sensing, medical imaging, recovery and separation of Ln (which have been identified as critical resources by the European Union) and (ii) the recent discovery of Ln-dependent bacteria. LBT and LanM have shown opposite selectivity trends along the Ln series. Although the understanding of such behaviour is essential to further advance the rational design and applications of Ln-binding peptides and proteins, the structural determinants for such different selectivity have not been established yet. Indeed, it is very difficult to obtain structural information on Ln-peptide/protein complexes using common techniques. This proposal aims to decipher the selectivity of LBT and LanM along the Ln series by investigating the coordination sphere of different Ln bound to LBT and LanM via L-edge X-ray absorption spectroscopy.