TonB-dependent ligand trapping in the BtuB transporter
| Autor: | Allan Mills, Hai-Tuong Le, Franck Duong |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Biophysics Biology Ligands Biochemistry 03 medical and health sciences Bacterial Proteins polycyclic compounds Inner membrane Binding site Binding Sites Escherichia coli Proteins Membrane Proteins Membrane Transport Proteins Biological Transport Transporter Cell Biology Periplasmic space biochemical phenomena metabolism and nutrition Ligand (biochemistry) Receptor–ligand kinetics Vitamin B 12 030104 developmental biology Scintillation proximity assay bacteria Bacterial outer membrane Bacterial Outer Membrane Proteins |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Biomembranes. 1858:3105-3112 |
| ISSN: | 0005-2736 |
| DOI: | 10.1016/j.bbamem.2016.09.019 |
| Popis: | TonB-dependent transporters are β-barrel outer membrane proteins occluded by a plug domain. Upon ligand binding, these transporters extend a periplasmic motif termed the TonB box. The TonB box permits the recruitment of the inner membrane protein complex TonB-ExbB-ExbD, which drives import of ligands in the cell periplasm. It is unknown precisely how the plug domain is moved aside during transport nor have the intermediate states between TonB recruitment and plug domain movement been characterized biochemically. Here we employ nanodiscs, native gel electrophoresis, and scintillation proximity assays to determine the binding kinetics of vitamin B12 to BtuB. The results show that ligand-bound BtuB recruits a monomer of TonB (TonB∆1-31), which in turn increases retention of vitamin B12 within the transporter. The TonB box and the extracellular residue valine 90 that forms part of the vitamin B12 binding site are essential for this event. These results identify a novel step in the TonB-dependent transport process. They show that TonB binding to BtuB trap the ligand, possibly until the ExbB-ExbD complex is activated or recruited to ensure subsequent transport. |
| Databáze: | OpenAIRE |
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