TonB-dependent transporters: regulation, structure, and function

By N. Noinaj, M. Guillier, Travis J. Barnard, S. Buchanan. Annual Review of Microbiology, 2010

898 citations recorded by the source corpus.

TonB-dependent transporters (TBDTs) are bacterial outer membrane proteins that bind and transport ferric chelates called siderophores, as well as vitamin B12, nickel complexes, and carbohydrates. The transport process requires energy in the form of protonmotive force and a complex of three inner membrane proteins, TonB-ExbB-ExbD, to transduce this energy to the outer membrane. The siderophore substrates range in complexity from simple small molecules such as citrate to large proteins like serum transferrin and haemoglobin. Because iron uptake is vital for almost all bacteria, expression of TBDTs is regulated in a number of ways that include metal-dependent regulators, σ/anti-σ factor systems, small RNAs, and even a riboswitch. In recent years many new structures of TBDTs have been solved in various states, resulting in a more complete picture of siderophore selectivity and binding, signal transduction across the outer membrane, and interaction with TonB-ExbB-ExbD. However, the transport mechanism is still unclear. In this review, we summarize recent progress in understanding regulation, structure and function in TBDTs and questions remaining to be answered.

Subfields: Cell Biology, Genetics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/87b16c44bd082a5fdff2ff6767f92ea0f28efd4e

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Citations in the corpus

• NsrA, a Predicted β-Barrel Outer Membrane Protein Involved in Plant Signal Perception and the Control of Secondary Infection in Sinorhizobium meliloti (2018, background): “Accordingly, the PRED-TMBB interface (20) (http://bioinformatics.biol.uoa.gr/PRED-TMBB) predicted 22 -strands found in porin-like outer membrane receptors such as FhuA and FecA, specifically using the posterior decoding algorithm (Fig.”
• Siderophores in environmental research: roles and applications (2014, background): “Thereafter , the Fe(III)–siderophore complex that is bound by a high-affinity periplasmic binding protein, which accompanied the complex to the cytoplasmic membrane, is released into the periplasmic space (Noinaj et al., 2010).”
• Microbial siderophores and their potential applications: a review (2016, background): “Siderophores bound to other heavy metals do not enter the cell efficiently whereas siderophore bound to iron moves into the cell adequately (Miethke and Marahiel 2007; Braud et al. 2009a; Noinaj et al. 2010).”