Investigating Landmodulin's EF Hands in Relation to Lanthanide Recycling Methods

Abstract

Rare earth elements (REEs) have distinct and varied electronic properties that have been applied for military and civilian use in electronics, such as cell phones and computer chip technologies. The recycling methods for REEs are complex and require a multitude of resources that prompt new studies to improve REEs separations. Lanmodulin (LanM), a protein that naturally bind to lanthanides, may provide a biological route for REE separation. Understanding the structure of LanM’s EF‐hands will explain how the lanthanides bond to them and lead to a greater understanding of how LanM can be used to recycle REEs to benefit our environment. The Summit Country Day School MSOE Center for BioMolecular Modeling MAPS Team used 3D modeling and printing technology to examine structure‐function relationships of EF1‐3 hands on lanmodulin. LanM has three tight binding EF‐hands, EF1 (D35‐E46), EF2 (D59‐E70), and EF3 (D84‐ E95), which are abundant in carboxylate side chains that bind the lanthanides. Lanthanide binding promotes a large conformational shift of the protein from a disorganized state to an organized state. The interior of the protein is a condensed helical bundle, and the majority of the exterior is composed of the EF hands, making bonding with lanthanides easier due to the EF hands being solely on the exterior. These three hands contain a higher number of coordination numbers (8‐9) compared to only 7 in Calmodulin (CaM), resulting in more specialized bonding properties. LanM also has a conserved proline between the first and second putative metal‐coordinating residues in each of the four EF hands, which is unique to this protein and may play a role in reducing affinity for calcium ions. In conclusion, analyzing the properties of the binding sites of EF1‐3 in LanM through 3D modeling can reveal insights on utilizing proteins as a method to extract and recycle REE in order to be environmentally cognizant.