Bazzone, Andre and Tesmer, Laura and Kurt, Derya and Kaback, H. Ronald and Fendler, Klaus and Madej, M. Gregor (2022) Investigation of sugar binding kinetics of the E. coli sugar/H+ symporter XylE using solid-supported membrane-based electrophysiology. JOURNAL OF BIOLOGICAL CHEMISTRY, 298 (2): 101505. ISSN , 1083-351X
Full text not available from this repository. (Request a copy)Abstract
Bacterial transporters are difficult to study using conventional electrophysiology because of their low transport rates and the small size of bacterial cells. Here, we applied solid-supported membrane-based electrophysiology to derive kinetic parameters of sugar translocation by the Escherichia coli xylose permease (XylE), including functionally relevant mutants. Many aspects of the fucose permease (FucP) and lactose permease (LacY) have also been investigated, which allow for more comprehensive conclusions regarding the mechanism of sugar translocation by transporters of the major facilitator superfamily. In all three of these symporters, we observed sugar binding and transport in real time to determine K-M, V-max, K-D, and k(obs) values for different sugar substrates. K-D and k(obs) values were attainable because of a conserved sugar-induced electrogenic conformational transition within these transporters. We also analyzed interactions between the residues in the available X-ray sugar/H+ symporter structures obtained with different bound sugars. We found that different sugars induce different conformational states, possibly correlating with different charge displacements in the electrophysiological assay upon sugar binding. Finally, we found that mutations in XylE altered the kinetics of glucose binding and transport, as Q175 and L297 are necessary for uncoupling H+ and D-glucose translocation. Based on the rates for the electrogenic conformational transition upon sugar binding (>300 s(-1)) and for sugar translocation (2 s(-1) - 30 s(-1) for different substrates), we propose a multiple-step mechanism and postulate an energy profile for sugar translocation. We also suggest a mechanism by which D-glucose can act as an inhibitor for XylE.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | LAC CARRIER PROTEIN; L-FUCOSE TRANSPORT; LACTOSE PERMEASE; ESCHERICHIA-COLI; MELIBIOSE PERMEASE; CRYSTAL-STRUCTURE; CHARGE TRANSLOCATION; LIGAND RECOGNITION; MONOMERIC ENZYMES; MECHANISM; |
| Subjects: | 500 Science > 500 Natural sciences & mathematics |
| Divisions: | Biology, Preclinical Medicine > Institut für Biophysik und physikalische Biochemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 26 Jan 2024 12:02 |
| Last Modified: | 26 Jan 2024 12:02 |
| URI: | https://pred.uni-regensburg.de/id/eprint/57811 |
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