Gating of TonB-dependent transporters by substrate-specific forced remodelling

• DOI: 10.1038/ncomms14804
• Publication Date: 2017-04-21T11:25:59Z
• Authors: Samuel J. Hickman; Rachael E. M. Cooper; Luca Bellucci; Emanuele Paci; David J. Brockwell
• Keywords: 0303 health sciences; Science; Escherichia coli Proteins; Spectrum Analysis; Q; Biophysics; Membrane Proteins; Membrane Transport Proteins; Molecular dynamics; Protein Engineering; Article; Substrate Specificity; 03 medical and health sciences; N/A; Bacterial Proteins; Gram-Negative Bacteria; Ion Channel Gating; Bacterial Outer Membrane Proteins; Protein Binding; Signal Transduction

AbstractMembrane proteins play vital roles in inside-out and outside-in signal transduction by responding to inputs that include mechanical stimuli. Mechanical gating may be mediated by the membrane or by protein(s) but evidence for the latter is scarce. Here we use force spectroscopy, protein engineering and bacterial growth assays to investigate the effects of force on complexes formed between TonB and TonB-dependent transporters (TBDT) from Gram-negative bacteria. We confirm the feasibility of protein-only mediated mechanical gating by demonstrating that the interaction between TonB and BtuB (a TBDT) is sufficiently strong under force to create a channel through the TBDT. In addition, by comparing the dimensions of the force-induced channel in BtuB and a second TBDT (FhuA), we show that the mechanical properties of the interaction are perfectly tuned to their function by inducing formation of a channel whose dimensions are tailored to the ligand.