What is the role of the TonB ExbB proteins in bacterial transport?
What is the role of the TonB ExbB proteins in bacterial transport?
The TonB/ExbB/ExbD type systems energize transport using the PMF- and TonB-dependent receptors. Examples of such receptors in E. coli include BtuB for vitamin B12 uptake and several receptors for the uptake of different iron–siderophore complexes.
How does TonB work?
TonB, embedded within the cytoplasmic membrane, is closely associated with the ExbB–ExbD complex. The binding of siderophores to the extracellular pockets of outer membrane receptors causes a TonB-independent allosteric transition that is propagated through the outer membrane.
What does TonB stand for?
Outer membrane receptors, also known as TonB-dependent receptors, are a family of beta barrel proteins named for their localization in the outer membrane of gram-negative bacteria.
Does TonB-dependent transport use ATP?
However the outer membrane lacks conventional energy resources of sufficient ion gradients or access to ATP. Instead, energy for active transport across the outer membrane is transduced from the cytoplasmic membrane proton motive force by three integral cytoplasmic membrane proteins, TonB-ExbB-ExbD.
What do siderophores do?
Siderophores are small molecular iron chelators that are produced by microbes and whose most notable function is to sequester iron from the host and provide this essential metal nutrient to microbes.
What do ABC transporters do?
ATP-binding cassette (ABC) transporters constitute a ubiquitous superfamily of integral membrane proteins that are responsible for the ATP-powered translocation of many substrates across membranes. The highly conserved ABC domains of ABC transporters provide the nucleotide-dependent engine that drives transport.
Is an example of siderophore?
Siderophores, natural or synthetic, can chelate metal ions other than iron ions. Examples include aluminium, gallium, chromium, copper, zinc, lead, manganese, cadmium, vanadium, zirconium, indium, plutonium, berkelium, californium, and uranium.
Is Enterobactin a siderophore?
Enterobactin is an archetypical siderophore with exceptionally high affinity for Fe3+ (Ka = 1052)9. Many Gram-negative bacteria, including E. coli10, produce and take up this siderophore. Other bacteria do not synthesise the molecule themselves, but will use it to scavenge iron in a piracy strategy11.
What are the two types of transporters?
There are two different types of transport; passive and active.
How many types of ABC transporters are there?
There are 48 ABC transporters in humans that can be subdivided by phylogenetic analysis into seven distinct subfamilies A-G [8,9].
Is ferritin a siderophore?
Ferritin is a much larger protein than transferrin and is capable of binding several thousand iron atoms in a nontoxic form. Siderophores are unable to directly mobilise iron from ferritin….Animal pathogens.
| Infection type | Organism | Siderophore |
|---|---|---|
| Anthrax | Bacillus anthracis | Petrobactin |
What is the function of siderophore?
What is the structure of A TonB-dependent receptor?
A complex of three membrane-spanning proteins TonB, ExbB and ExbD couples the chemiosmotic potential of the cytoplasmic membrane with siderophore uptake across the outer membrane. The crystallographic structures of two TonB-dependent receptors (FhuA and FepA) have recently been determined.
What are the proteins that interact with TonB?
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, LbpA and TbpA. The TonB protein also interacts with some colicins.
How is siderophore uptake dependent on the presence of Tonb?
Siderophore uptake across the outer membrane is dependent upon the presence of a complex of three cytoplasmic membrane proteins TonB, ExbB and ExbD, and their ability to couple a proton gradient with siderophore transport. Hence, this family of active outer membrane transport proteins has been termed TonB-dependent receptors.
What is the role of Tonb receptors in Gram negative bacteria?
TonB-dependent receptors in gram-negative bacteria are associated with the uptake and transport of large substrates such as iron siderophore complexes and vitamin B12.