A lanmodulin homologous protein, from Mesorhizobium qingshengii J19, involved in yttrium immobilization.

The increasing demand for rare earth elements (REEs) drives the need for sustainable recovery strategies, particularly those based on biological systems. Recent studies have highlighted the role of lanthanide series (LnIIIs) in bacterial processes, focusing on proteins capable of selectively recognizing and binding these metals. Among them, Lanmodulin (LanM) from Methylorubrum extorquens AM1, containing four EF-hand motifs, has been identified as highly selective for LnIII over calcium (Ca). Based on these findings, we studied a homologous EF-hand protein from Mesorhizobium qingshengii J19, a bacterium resistant to high concentrations of yttrium (Y). The corresponding gene was cloned and overexpressed in Escherichia coli BL21 to assess its metal-binding capabilities. Engineered cells co-incubated with neodymium (Nd) and Y exhibited increased accumulation of both metals. The purified recombinant protein matched the predicted molecular weight and was identified via Orbitrap-LC-MS as the EF-hand domain-containing protein. Protein-metal binding assays confirmed its affinity for Nd, while exhibiting higher levels for Y under the tested conditions. Overall, these results suggest that the EF-hand protein represents a promising bio-based tool for REE recovery and recycling from contaminated environments.