Ton B-dependent Receptors
The TonB-dependent receptors are a family of beta-barrel proteins from the outer membrane of Gram-negative bacteria. TonB complexes sense signals from outside of bacterial cells and transmit them via two membranes into the cytoplasm, leading to transcriptional activation of target genes.
In Escherichia coli, the TonB protein interacts with outer membrane receptor proteins that carry out high-affinity binding and energy-dependent uptake of specific substrates into the periplasmic space. These substrates are either poorly transported through non-specific porin channels or are encountered at very low concentrations. In the absence of TonB, these receptors bind their substrates but do not carry out active transport. TonB-dependent regulatory systems consist of six protein protein components.
The proteins that are currently known or presumed to interact with TonB include BtuB, CirA, FatA, FcuT, FecA, FhuA, FhuE, FepA, FptA, HemR, IrgA, IutA, PfeA, PupA and Tbp1. The TonB protein also interacts with some colicins. Most of these proteins contain a short conserved region at their N-terminus.
TonB receptors also play a role in phage predation, and are known to be critical receptors for phage binding in certain bacterial taxa.
Read more about Ton B-dependent Receptors: TonB-dependent Receptor Plug Domain
Famous quotes containing the words ton and/or receptors:
“Hearing your words, and not a word among them
Tuned to my liking, on a salty day
When inland woods were pushed by winds, that flung them
Hissing to leeward like a ton of spray,”
—Edna St. Vincent Millay (1892–1950)
“Our talk of external things, our very notion of things, is just a conceptual apparatus that helps us to foresee and control the triggerings of our sensory receptors in the light of previous triggering of our sensory receptors.”
—Willard Van Orman Quine (b. 1908)