In vivo evidence for FhuA outer membrane receptor interaction with the TonB inner membrane protein of <i>Escherichia coli</i>

Günter, Karolin; Braun, Volkmar

doi:10.1016/0014-5793(90)81335-l

Cited by 73 publications

(1 citation statement)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Periplasmic FhuD (31 kDa) and cytoplasmic-membrane-associated FhuC (29 kDa) and FhuB (41 kDa) are proteins necessary for the transport of ferrichrome and other Fe 3+ -hydroxamate compounds (Fe 3+ -aerobactin, Fe 3+ -coprogen) across the cytoplasmic membrane from the periplasm into the cytoplasm [34-36]. The protein complex TonB-ExbB-ExbD [37,38] provides energy for this process. The presence of genes encoding these proteins suggests a functional iron siderophore transport complex in O. carboxidovorans .…”

Section: Resultsmentioning

confidence: 99%

Complete genome and comparative analysis of the chemolithoautotrophic bacterium Oligotropha carboxidovorans OM5

et al. 2010

View full text Add to dashboard Cite

BackgroundOligotropha carboxidovorans OM5 T. (DSM 1227, ATCC 49405) is a chemolithoautotrophic bacterium capable of utilizing CO (carbon monoxide) and fixing CO2 (carbon dioxide). We previously published the draft genome of this organism and recently submitted the complete genome sequence to GenBank.ResultsThe genome sequence of the chemolithoautotrophic bacterium Oligotropha carboxidovorans OM5 consists of a 3.74-Mb chromosome and a 133-kb megaplasmid that contains the genes responsible for utilization of carbon monoxide, carbon dioxide, and hydrogen. To our knowledge, this strain is the first one to be sequenced in the genus Oligotropha, the closest fully sequenced relatives being Bradyrhizobium sp. BTAi and USDA110 and Nitrobacter hamburgiensis X14. Analysis of the O. carboxidovorans genome reveals potential links between plasmid-encoded chemolithoautotrophy and chromosomally-encoded lipid metabolism. Comparative analysis of O. carboxidovorans with closely related species revealed differences in metabolic pathways, particularly in carbohydrate and lipid metabolism, as well as transport pathways.ConclusionOligotropha, Bradyrhizobium sp and Nitrobacter hamburgiensis X14 are phylogenetically proximal. Although there is significant conservation of genome organization between the species, there are major differences in many metabolic pathways that reflect the adaptive strategies unique to each species.

show abstract

Section: Resultsmentioning

confidence: 99%

Complete genome and comparative analysis of the chemolithoautotrophic bacterium Oligotropha carboxidovorans OM5

et al. 2010

View full text Add to dashboard Cite

show abstract

Conversion of the FhuA transport protein into a diffusion channel through the outer membrane of Escherichia coli.

1993

View full text Add to dashboard Cite

The FhuA receptor protein is involved in energy‐coupled transport of Fe3+ via ferrichrome through the outer membrane of Escherichia coli. Since no energy source is known in the outer membrane it is assumed that energy is provided through the action of the TonB, ExbB and ExbD proteins, which are anchored to the cytoplasmic membrane. By deleting 34 amino acid residues of a putative cell surface exposed loop, FhuA was converted from a ligand specific transport protein into a TonB independent and nonspecific diffusion channel. The FhuA deletion derivative FhuA delta 322–355 formed stable channels in black lipid membranes, in contrast to wild‐type FhuA which did not increase membrane conductance. The single‐channel conductance of the FhuA mutant channels was at least three times larger than that of the general diffusion porins of E. coli outer membrane. It is proposed that the basic structure of FhuA in the outer membrane is a channel formed by beta‐barrels. Since the loop extending from residue 316 to 356 is part of the active site of FhuA, it probably controls the permeability of the channel. The transport‐active conformation of FhuA is mediated by a TonB‐induced conformational change in response to the energized cytoplasmic membrane. The ferrichrome transport rate into cells expressing FhuA delta 322–355 increased linearly with increasing substrate concentration (from 0.5 to 20 microM), in contrast to FhuA wild‐type cells, which displayed saturation at 5 microM. This implies that in wild‐type cells ferrichrome transport through the outer membrane is the rate‐limiting step and that TonB, ExbB and ExbD are only required for outer membrane transport.

show abstract

Signal transfer through three compartments: transcription initiation of the Escherichia coli ferric citrate transport system from the cell surface.

et al. 1995

View full text Add to dashboard Cite

Transport of ferric citrate into cells of Escherichia coli K‐12 involves two energy‐coupled transport systems, one across the outer membrane and one across the cytoplasmic membrane. Previously, we have shown that ferric citrate does not have to enter the cytoplasm of E. coli K‐12 to induce transcription of the fec ferric citrate transport genes. Here we demonstrate that ferric citrate uptake into the periplasmic space between the outer and the cytoplasmic membranes is not required for fec gene induction. Rather, FecA and the TonB, ExbB and ExbD proteins are involved in induction of the fec transport genes independent of their role in ferric citrate transport across the outer membrane. The uptake of ferric citrate into the periplasmic space of fecA and tonB mutants via diffusion through the porin channels did not induce transcription of fec transport genes. Point mutants in FecA displayed the constitutive expression of fec transport genes in the absence of ferric citrate but still required TonB, with the exception of one FecA mutant which showed a TonB‐independent induction. The phenotype of the FecA mutants suggests a signal transduction mechanism across three compartments: the outer membrane, the periplasmic space and the cytoplasmic membrane. The signal is triggered upon the interaction of ferric citrate with FecA protein. It is postulated that FecA, TonB, ExbB and ExbD transfer the signal across the outer membrane, while the regulatory protein FecR transmits the signal across the cytoplasmic membrane to FecI in the cytoplasm. FecI serves as a sigma factor which facilitates binding of the RNA polymerase to the fec transport gene promoter upstream of fecA.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

In vivo evidence for FhuA outer membrane receptor interaction with the TonB inner membrane protein of Escherichia coli

Cited by 73 publications

References 8 publications

Complete genome and comparative analysis of the chemolithoautotrophic bacterium Oligotropha carboxidovorans OM5

Complete genome and comparative analysis of the chemolithoautotrophic bacterium Oligotropha carboxidovorans OM5

Conversion of the FhuA transport protein into a diffusion channel through the outer membrane of Escherichia coli.

Signal transfer through three compartments: transcription initiation of the Escherichia coli ferric citrate transport system from the cell surface.

Contact Info

Product

Resources

About