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. Author manuscript; available in PMC: 2017 Jul 18.
Published in final edited form as: Essays Biochem. 2017 May 9;61(2):211–223. doi: 10.1042/EBC20160084

Figure 2.

Figure 2

TonB-dependent transport by Gram-negative bacteria. Ligand binding at the TBDT (1), which can be mediated by a co-receptor (shown), results in conformational changes in the transporter. An interaction between the TonB box of the TBDT and the TonB–ExbB–ExbD complex occurs (2). Subsequently, the TonB complex provides energy for ligand transport across the OM (3, 4). After entry into the periplasm, most ligands are bound by a PBP (5). The PBP shuttles the ligand to an ABC transporter (6) that mediates transport across the IM (7). Abbreviations: OM, outer membrane; IM, inner membrane; TBDT, TonB-dependent transporter; PBP, periplasmic binding protein; ABC, ATP-binding cassette.