Conformational dynamics and regulation of bacterial type I maltose ABC transporters
Final Report Abstract
A major goal of our project was to identify interactions of ABC importers with their cognate solute binding proteins (SBP) as well as with inhibitory proteins at the molecular level. We have demonstrated for the first time that contacts of the N- and C-terminal lobes of a liganded binding protein with the respective transporter are dependent on the structural organization of the SBP-freely diffusible or covalently bound to a transmembrane domain. Furthermore, regulatory proteins such as EIIAGlc and P-Ser46-HPr which mediate inducer exclusion in E. coli and L. casei, respectively, block the transport cycle by interaction with the nucleotide-binding subunits of inhibition-sensitive ABC importers. In case of EIIAGlc we were able to demonstrate that the protein binds to all conformational states of the maltose transporter MaFGK2 and prevents closing of the MalK dimer upon binding of ATP and liganded maltose binding protein, MalE. Our results on the heterodimeric ABC transporter TM287/288 support the notion that ATP binding is sufficient to switch the transporters to the OF state and hydrolysis is required to reset the transport cycle. Additionally, we discovered equilibrium between the IF and OF state independent of the hydrolysis reaction. We anticipate that our results provide a mechanistic framework to understand the functional role of the extracellular gate of type I ABC exporters and to explain the molecular underpinning of disease-causing mutations found in the extracellular region of medically important ABC exporters as recently investigated for MRP1 and CFTR.
Publications
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(2016) Mode of interaction of the signal-transducing protein EIIAGlc with the maltose ABC transporter in the process of inducer exclusion. Biochemistry 55, 5442-5452
Wuttge, S., Licht, A., Timachi, M.H., Bordignon, E., and Schneider, E.
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(2017) Exploring conformational equilibria of a heterodimeric ABC transporter eLife
Timachi, M.H., Hutter C.A.J., Hohl, M., Assafa, T., Böhm, S., Mittal, A., Seeger, M.A., Bordignon, E.
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(2017) Inducer exclusion in Firmicutes: insights into the regulation of a carbohydrate ATP binding cassette transporter from Lactobacillus casei BL23 by the signal transducing protein P-Ser46-HPr Mol. Microbiol. 105, 25-45
Homburg, C., Bommer, M., Wuttge, S., Hobe, C., Beck, S., Dobbek, H., Deutscher, J., Licht, A., and Schneider, E.
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(2018) Atomistic Mechanism of Large-Scale Conformational Transition in a Heterodimeric ABC Exporter Journal of the American Chemical Society, 140, 4543-4551
Göddeke, H., Timachi, M.H., Hutter, C.A.J., Galazzo, L., Seeger, M.A., Karttunen, M., Bordignon, E., Schäfer, L.V.
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(2018) Probing the extracellular gate of an ABC exporter by conformation-specific single domain antibodies
Hutter, C. A., Timachi, M. H., Hürlimann, L. M., Kucher, S., Zimmermann, I., Eglof, P., Göddeke, H., Karttunen, M., Schäfer, L. V., Bordignon E., Seeger, M. A.
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(2019) Structural and functional characterization of a maltose/maltodextrin ABC transporter comprising a single solute binding domain (MalE) fused to the transmembrane subunit MalF. Res. Microbiol.
Licht, A., Bommer, M., Werther, T., Neumann, K., Hobe, C., and Schneider, E.
