Structure-function studies of Borrelia metal transport A (BmtA) from Lyme disease-causing Borrelia burgdorferi

Abstract

Lyme disease, caused by the spirochetal bacterium Borrelia burgdorferi, remains the most prevalent vector-borne illness in humans. Addressing challenges such as antibiotic resistance, persistent infection, and complex disease dynamics requires identifying novel therapeutic targets. Manganese (Mn²˖) is essential for the survival of burgdorferi, serving as a cofactor for enzymes that protect against oxidative stress, particularly superoxide dismutase. The Borrelia metal transporter A (BmtA), a membra protein responsible for Mn²˖ uptake, is critical for bacterial infectivity, making it a promising drug target. This study characterized the structural and functional properties BmtA to elucidate its role in manganese transport. A structural model was generated using AlphaFold2 and compared with bacterial and mammalian ZIP transporters to identify metal-binding residues. Site-directed mutagenesis and functional analyses in a yeast expression system, combined with PAR metal-binding and ICP-MS assays, identified residues H133, E137, and E203 as essential for Mn²˖ transport. Zinc was also found to stabilize BmtA, with deficiency resulting in protein degradation.

For biochemical characterization, optimal solubilization and purification were achieved using n-Dodecyl-β-D-Maltopyranoside (DDM), maintaining the protein’s dimeric stat as confirmed by Blue Native PAGE and crosslinking experiments. Metal-binding and thermal shift assays demonstrated that Mn²˖ induced conformational stabilization, whereas Zn²˖ had minimal impact. Mutations at key residues disrupted folding and stability, highlighting the importance of metal coordination.Overall, this study enhance understanding of BmtA’s structure–function relationship and supports its potential as a therapeutic target for combating Lyme disease.

Thesis is embargoed until 31 December 2026.

Date of Award	Dec 2025
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Libyan Government
Supervisor	Edel Hyland (Supervisor) & Geoffrey Gobert (Supervisor)