PhoE protein pores in the outer membrane of Escherichia coli K-12 not only have a preference for Pi and Pi-containing solutes but are general anion-preferring channels

Korteland, Jaap; Graaff, Pieter de; Lugtenberg, Ben

doi:10.1016/0005-2736(84)90374-2

Cited by 28 publications

(9 citation statements)

References 30 publications

(29 reference statements)

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“…Our finding that the macroscopic current through patches containing multiple PhoE pores is affected by ATP and aspartate is in agreement with previous reports that there does not appear to be a specificity for polyphosphates, but rather a general anion selectivity [4, 7]. However, we must keep in mind that the two compounds affect PhoE differently, since aspartate does not promote kinetic effects in addition to macroscopic current reduction, while ATP does; at this point, it is hard to distinguish whether this difference is due to the fact that ATP is a more charged and longer molecule, or whether the types of interaction with PhoE are really distinct.…”

Section: Discussionsupporting

confidence: 93%

Distinct sensitivities of OmpF and PhoE porins to charged modulators

Samartzidou

Delcour

1999

FEBS Letters

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The inhibition of the anion-selective PhoE porin by ATP and of the cation-selective OmpF porin by polyamines has been previously documented. In the present study, we have extended the comparison of the inhibitor-porin pairs by investigating the effect of anions (ATP and aspartate) and positively charged polyamines (spermine and cadaverine) on both OmpF and PhoE with the patch-clamp technique, and by comparing directly the gating kinetics of the channels modulated by their respective substrates. The novel findings reported here are (1) that the activity of PhoE is completely unaffected by polyamines, and (2) that the kinetic changes induced by ATP on PhoE or polyamines on OmpF suggest different mechanisms of inhibition. ATP induces a high degree of flickering in the PhoEmediated current and appears to behave as a blocker of ion flow during its presumed transport through PhoE. Polyamines modulate the kinetics of openings and closings of OmpF, in addition to promoting a blocker-like flickering activity. The strong correlation between sensitivity to inhibitors and ion selectivity suggests that some common molecular determinants are involved in these two properties and is in agreement with the hypothesis that polyamines bind inside the pore of cationic porins.z 1999 Federation of European Biochemical Societies.

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Section: Discussionsupporting

confidence: 93%

Distinct sensitivities of OmpF and PhoE porins to charged modulators

Samartzidou

Delcour

1999

FEBS Letters

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“…Hydrophilic substrates with molecular masses below 700 Da diffuse through the channels formed by the porins OmpF and OmpC. Examples for facilitated diffusion involving stereospecific recognition between substrate and porin are the maltodextrins which enter through the LamB pore (40), sucrose via the ScrY protein (52), nucleosides through the Tsx pore (6,27), and phosphates through the PhoE pore (5,37). Weiss et al (63) proposed an atomic model based on high-resolution X-ray crystallographic data for the Rhodobacter capsulatus porin, the basic features of which also seem to apply for the other porins, including OmpF, OmpC, LamB, and PhoE (47) and presumably Tsx (10) and the ScrY protein (54).…”

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confidence: 99%

Insertion derivatives containing segments of up to 16 amino acids identify surface- and periplasm-exposed regions of the FhuA outer membrane receptor of Escherichia coli K-12

1993

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The FhuA receptor in the outer membrane of Escherichwa coli K-12 is involved in the uptake of ferrichrome, colicin M, and the antibiotic albomycin and in infection by phages Ti, T5, and +80. Fragments of up to 16 amino acid residues were inserted into FhuA and used to determine FhuA active sites and FhuA topology in the outer membrane. For this purpose antibiotic resistance boxes flanked by symmetric polylinkers were inserted intohuiA and subsequently partially deleted. Additional in-frame insertions were generated by mutagenesis with transposon Tnl 725. The 68 FhuA protein derivatives examined contained segments of 4, 8, 12, 16, and 22 additional amino acid residues at 34 different locations from residues 5 to 646 of the mature protein. Most of the FhuA derivatives were found in normal amounts in the outer membrane fraction. Half of these were fully active toward all ligands, demonstrating proper insertion into the outer membrane. Seven of the 12-and 16-amino-acid-insertion derivatives (at residues 378, 402, 405, 415, 417, 456, and 646) were active toward all of the ligands and could be cleaved by subtilisin in whole cells, suggesting a surface location of the extra loops at sites which did not affect FhuA function. Two mutants were sensitive to subtilisin (insertions at residues 511 and 321) but displayed a strongly reduced sensitivity to colicin M and to phages +80 and Ti. Four of the insertion derivatives (at residues 162, 223, 369, and 531) were cleaved only in spheroplasts and probably form loops at the periplasmic side of the outer membrane. The number and size of the proteolytic fragments indicate cleavage at or close to the sites of insertion, which has been proved for five insertions by amino acid sequencing.Most mutants with functional defects were affected in their sensitivity to all ligands, yet frequently to different degrees. Some mutants showed a specifically altered sensitivity to a few ligands; for example, mutant 511-04 was partially resistant only to colicin M, mutant 241-04 was reduced in ferrichrome and albomycin uptake and showed a reduced colicin M sensitivity, and mutant 321-04 was fully resistant to phage Ti and partially resistant to phage +80. The altered residues define preferential binding sites for these ligands. Insertions of 4 to 16 residues at positions 69, 70, 402, 530, 564, and 572 resulted in strongly reduced amounts of FhuA in the outer membrane fraction, varying in function from fully active to inactive. These results provide the basis for a model of FhuA organization in the outer membrane.Uptake of substrates across the outer membrane of Escherichia coli occurs via diffusion, facilitated diffusion, and receptor-dependent transport. Hydrophilic substrates with molecular masses below 700 Da diffuse through the channels formed by the porins OmpF and OmpC. Examples for facilitated diffusion involving stereospecific recognition between substrate and porin are the maltodextrins which enter through the LamB pore (40), sucrose via the ScrY protein (52), nucleosides through the Ts...

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“….The functional form of PhoE is a trimer which forms channels in the outer membrane through which small hydrophilic compounds can pass [21,22]. We have postulated a model for the folding of PhoE based on genetic experiments and general prediction methods.…”

Section: Advantages Of Using Outer Membrane Protein Phoe As a Carriermentioning

confidence: 99%

PhoE Protein as a Carrier for Foreign Epitopes

Janssen

Tommassen

1994

International Reviews of Immunology

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Outer membrane protein PhoE of E. coli appears to be a suitable carrier for the expression of foreign antigenic determinants at the bacterial cell-surface. Insertion of stretches of amino acids in the cell-surface exposed regions of PhoE does not interfere with the biogenesis of the protein. Dependent on the cell-surface exposed loop used for insertion and the character of the inserted amino acids up to 50 amino acids could be inserted. Both B-cell epitopes and T-cell epitopes remain antigenic and immunogenic in the PhoE-associated conformation. However, flanking amino acids can interfere with the antigenicity and immunogenicity of T-cell epitopes inserted in PhoE. Because E. coli PhoE can be expressed in attenuated Salmonella and Shigella strains, it seems to be a suitable vaccine carrier candidate.

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PhoE protein pores in the outer membrane of Escherichia coli K-12 not only have a preference for Pi and Pi-containing solutes but are general anion-preferring channels

Cited by 28 publications

References 30 publications

Distinct sensitivities of OmpF and PhoE porins to charged modulators

Distinct sensitivities of OmpF and PhoE porins to charged modulators

Insertion derivatives containing segments of up to 16 amino acids identify surface- and periplasm-exposed regions of the FhuA outer membrane receptor of Escherichia coli K-12

PhoE Protein as a Carrier for Foreign Epitopes

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