Probing the Function of Lanthanide-Binding Proteins from Environmental Bacteria
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Author:
Hamilton, Tim
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Joseph Alfred Cotruvo, Jr., Thesis Supervisor Daniel J Cosgrove, Thesis Honors Advisor
Keywords:
Lanthanide Protein Rare Earth Element Bacteria
Abstract:
Recently has it been shown that certain methylotrophic bacteria selectively uptake and store heavy lanthanides (Lns). Here we investigate two LnIII-binding proteins from a Beijerinckiaceae RH AL1 (RHAL1) and a Hansschlegelia (Hans) bacterium, which we have named RHAL1 LanM and Hans LanM, respectively. Both proteins exhibit significant homology to lanmodulin (LanM), a well-characterized LnIII-binding protein within Methylorubrum extorquens (Me), except for differences in functionally relevant Asp, Asn, and Pro residues within their four EF-hand metal-binding motifs. Preliminary data suggested that these proteins might possess unique selectivity among the Lns, not seen in Me LanM. We use Ultraviolet-visible (UV-vis) spectrophotometry and spectrofluorometric LnIII titrations, as well as Xylenol Orange (XO) competition assays, and spectrofluorometric chelator-inducted desorption experiments to demonstrate that RHAL1 LanM and Hans LanM bind fewer Lns than Me LanM, and that Hans LanM is the most selective for lighter Lns over heavier Lns, among the three proteins. This work provides a more complete understanding of how Biology senses, acquires, a regulates Lns, and may inspire the mining industry to use this unique metal selectivity to address the supply chain shortages for these valuable Rare Earth Elements (REEs).
