Discovery and molecular investigation of mycobacterial transporters responsible for iron acquisition

Objetivo

To infect humans, the devastating pathogen Mycobacterium tuberculosis critically depends on two closely related siderophores – soluble carboxymycobactin and membrane-bound mycobactin – which capture iron with high affinity inside the host cell. Despite their undisputed importance for virulence, little is known about how these siderophores are exported and imported across the two mycobacterial membranes.
Building on my lab’s experience in elucidating transport processes of pathogenic bacteria, we will unravel the molecular mechanism of an unusual ABC exporter which is thought to import iron-loaded siderophores across the inner mycobacterial membrane and to release iron in the cytoplasm by virtue of its attached siderophore interacting domain. Further, we will investigate two proton-driven transporters responsible for the efflux of empty siderophores, exhibiting an unknown protein fold. We will determine atomic structures by combining X-ray crystallography and cryo-EM and thoroughly investigate active in- and efflux of siderophores in liposomes as well as in cells.
Siderophore transport across the outer mycobacterial membrane is a terra incognita. By combining high-density transposon mutagenesis with deep sequencing (Tn-Seq), we aim to discover novel receptors, carriers and channels involved in siderophore transport, which are subsequently characterized at the biochemical and structural level.
Siderophore-mediated iron acquisition offers a vulnerable attacking point of M. tuberculosis. Using protein engineering, we will develop a human siderocalin exhibiting low affinity binding for carboxymycobactin into a therapeutic agent able to efficiently capture mycobacterial siderophores and thereby starve M. tuberculosis for iron.
In summary, we will discover novel proteins involved in iron acquisition, gain mechanistic insights into poorly understood siderophore transport processes at the molecular level and explore novel strategies to treat tuberculosis.