TonB-dependent outer membrane ferric citrate transporter and signal transducer; FecA is the outer membrane receptor protein in the Fe(3+) dicitrate transport system.

Ferric citrate ABC transporter periplasmic binding protein; Binds citrate-dependent Fe(3+); part of the binding-protein- dependent transport system for uptake of citrate-dependent Fe(3+).

Membrane spanning protein in TonB-ExbB-ExbD complex; Involved in the TonB-dependent energy-dependent transport of various receptor-bound substrates.

Membrane spanning protein in TonB-ExbB-ExbD complex; Involved in the TonB-dependent energy-dependent transport of various receptor-bound substrates. Protects ExbD from proteolytic degradation and functionally stabilizes TonB.

Ferrichrome outer membrane transporter; Involved in the uptake of iron in complex with ferrichrome, a hydroxamate-type siderophore. Binds and transports ferrichrome-iron across the outer membrane. In addition to its role in ferrichrome-iron transport, transports the antibiotic albomycin, which is a structural analog of ferrichrome, and acts as a receptor for colicin M, microcin J25 and bacteriophages T1, T5, phi80 and UC-1. The energy source, which is required for all FhuA functions except infection by phage T5, is provided by the inner membrane TonB system.

Ferric citrate ABC transporter permease; Part of the binding-protein-dependent transport system for citrate-dependent Fe(3+). Probably responsible for the translocation of the substrate across the membrane.

RNA polymerase, sigma 54 (sigma N) factor; Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. This sigma factor is responsible for the expression of enzymes involved in arginine catabolism. The open complex (sigma-54 and core RNA polymerase) serves as the receptor for the receipt of the melting signal from the remotely bound activator protein GlnG(NtrC).

Anti-sigma factor; An anti-sigma factor for extracytoplasmic function (ECF) sigma factor sigma-E (RpoE). ECF sigma factors are held in an inactive form by an anti-sigma factor until released by regulated intramembrane proteolysis (RIP). RIP occurs when an extracytoplasmic signal triggers a concerted proteolytic cascade to transmit information and elicit cellular responses. The membrane-spanning regulatory substrate protein is first cut periplasmically (site-1 protease, S1P, DegS), then within the membrane itself (site-2 protease, S2P, RseP), while cytoplasmic proteases finish degrading [...]

Membrane spanning protein in TonB-ExbB-ExbD transport complex; Interacts with outer membrane receptor proteins that carry out high-affinity binding and energy dependent uptake into the periplasmic space of specific substrates such as cobalamin, and various iron compounds (such as iron dicitrate, enterochelin, aerobactin, etc.). In the absence of TonB these receptors bind their substrates but do not carry out active transport. TonB also interacts with some colicins and is involved in the energy-dependent, irreversible steps of bacteriophages phi 80 and T1 infection. It could act to tran [...]