Membrane proteins; Multidrug efflux pumps; ABC transporter; MFS transporter; Pathogenic bacteria; Antibiotic resistance; Mycobacterium tuberculosis; Enterococcus faecalis; Drug efflux; Virulence factors; Mycobacterial lipids; Siderophore transport; Iron sequestration; X-ray crystallography; Structure-based biochemistry
Hutter Cedric A. J., Timachi M. Hadi, Hürlimann Lea M., Zimmermann Iwan, Egloff Pascal, Göddeke Hendrik, Kucher Svetlana, Štefanić Saša, Karttunen Mikko, Schäfer Lars V., Bordignon Enrica, Seeger Markus A. (2019), The extracellular gate shapes the energy profile of an ABC exporter, in Nature Communications
, 10(1), 2260-2260.
Egloff Pascal, Zimmermann Iwan, Arnold Fabian M., Hutter Cedric A. J., Morger Damien, Opitz Lennart, Poveda Lucy, Keserue Hans-Anton, Panse Christian, Roschitzki Bernd, Seeger Markus A. (2019), Engineered peptide barcodes for in-depth analyses of binding protein libraries, in Nature Methods
, 16(5), 421-428.
Seeger Markus A., Hiller Sebastian, Kaur Hundeep, Hartmann Jean-Baptiste, Jakob Roman P., Zahn Michael, Zimmermann Iwan, Maier Timm (2019), Identification of conformation-selective nanobodies against the membrane protein insertase BamA by an integrated structural biology approach, in Journal of Biomolecular NMR
Hohl Michael, Remm Sille, Eskandarian Haig A., Dal Molin Michael, Arnold Fabian M., Hürlimann Lea M., Krügel Andri, Fantner Georg E., Sander Peter, Seeger Markus A. (2019), Increased drug permeability of a stiffened mycobacterial outer membrane in cells lacking MFS transporter Rv1410 and lipoprotein LprG, in Molecular Microbiology
, 111(5), 1263-1282.
Bräuer Philipp, Parker Joanne L., Gerondopoulos Andreas, Zimmermann Iwan, Seeger Markus A., Barr Francis A., Newstead Simon (2019), Structural basis for pH-dependent retrieval of ER proteins from the Golgi by the KDEL receptor, in Science
, 363(6431), 1103-1107.
Uptake and extrusion of molecules across the lipid bilayer are vital cellular processes mediated by transmembrane proteins. Despite their physiological importance, membrane transporters are poorly characterized at the biochemical and structural level.ATP binding cassette (ABC) exporters and major facilitator superfamily (MFS) transporters belong to two large transporter superfamilies and pump substrates against their concentration gradient by harnessing the energy of ATP hydrolysis and the proton motive force, respectively. ABC exporters are closely related at the sequence level and share the same structural fold. However, their substrate specificities and physiological functions are remarkably diverse. Because only few ABC exporter structures exist, molecular determinants of substrate specificity remain largely elusive. In pathogenic bacteria, ABC exporters pump antibiotics and other noxious substances out of the cell and thereby mediate multidrug resistance. The molecular mechanism by which drug efflux pumps are capable of extruding a myriad of different compounds remains ill-defined. Transport processes play also a vital role in the uptake of essential nutrients such as iron and the export of lipids from the cytoplasm. M. tuberculosis depends on its iron siderophores mycobactin and carboxymycobactin to replicate in macrophages. Mycobactin-mediated iron uptake requires the heterodimeric ABC exporter IrtAB, but the actual substrate recognized by this transporter remains to be elucidated. Mycobacteria synthesize glycosylated lipids called lipoarabinomannans (LAMs), which need to be incorporated into the complex mycobacterial cell wall in a process that is crucial for virulence of M. tuberculosis. The MFS transporter Rv1410 and the liproprotein LprG are responsible for LAM incorporation by a mechanism that remains elusive.By combining protein biochemistry, X-ray crystallography, molecular microbiology and bacterial genetics we will obtain novel insights into:1) The molecular mechanism of heterodimeric ABC exporters by solving the structure of TM287/288 in its outward-facing and/or outward-occluded state and by studying the functional role of its extracellular gate. 2) Molecular hallmarks of multidrug ABC exporters by investigating seven closely related heterodimeric ABC exporters of E. faecalis of which only a subset is capable of multidrug efflux.3) The functional role of the mycobacterial ABC exporter IrtAB and its attached siderophore interaction domain in the transport and reduction of iron bound to mycobactin and carboxymycobactin.4) The molecular interplay between the MFS transporter Rv1410 and the liproprotein LprG to display LAMs at the cellular surface of Mycobacteria.In summary, our work will shed light on the molecular mechanisms of transporters responsible for drug efflux, iron uptake and lipid transport in pathogenic bacteria.