Disease relevance of ECs0268

• The selectivity filter of voltage-dependent channels formed by phosphoporin (PhoE protein) from E. coli [1].
• Three regions within the N-terminal 130 amino acids were localized which determine pore characteristics and a segment between residues 75 and 110 contains amino acids which determine specificity for PhoE phages [2].
• To identify the requirements for the biogenesis of outer-membrane proteins in Gram-negative bacteria, the sorting and assembly of the trimeric, pore-forming protein PhoE was studied in vitro [3].
• When Shigella flexneri was starved for P1, neither PhoE nor alkaline phosphatase was produced [4].
• Furthermore, the possibility for expression of PhoE constructs in attenuated Salmonella typhimurium strains offers the exciting prospect of new types of live oral vaccines expressing selected combinations of B and T cell epitopes [5].

High impact information on ECs0268

• Both slow kinetics and inverse voltage-dependence are removed when 70 amino acids from the N-terminal of OmpF are introduced into the homologous region of PhoE [6].
• To address these questions, we have made use of the known 3D-structure of the trimeric porin PhoE of Escherichia coli to engineer intramolecular disulfide bridges into this protein at positions that are not exposed to the periplasm once the protein is correctly assembled [7].
• In addition, several PhoE mutants with amino acid substitutions and insertions in either the L3 or L4 loop of the monomer exhibited pressure sensitivity comparable with the wild-type OmpC porin [8].
• Analysis of amino acid sequences reported for the major outer membrane proteins of Escherichia coli, including the porins (OmpF, OmpC, and PhoE), the phage lambda receptor (LamB), and another protein (OmpA), revealed several regions of local homology that is statistically significant [9].
• Pore formation and function of phosphoporin PhoE of Escherichia coli are determined by the core sugar moiety of lipopolysaccharide [10].

Chemical compound and disease context of ECs0268

• In vitro insertion and assembly of outer membrane protein PhoE of Escherichia coli K-12 into the outer membrane. Role of Triton X-100 [11].
• Role of the carboxy-terminal phenylalanine in the biogenesis of outer membrane protein PhoE of Escherichia coli K-12 [12].
• The three-dimensional structure of PhoE porin from Escherichia coli, negatively stained with uranyl acetate, has been determined by electron crystallographic techniques to a resolution of about 18 A. The structure shows that PhoE porin consists of trimeric stain-filled channels as the basic unit [13].
• Tryptophan fluorescence study on the interaction of the signal peptide of the Escherichia coli outer membrane protein PhoE with model membranes [14].
• The experimental system selected for testing the accuracy of this concept was the reversible dissociation of a proton from a single pyranine molecule (8-hydroxypyrene-1,2,3-trisulfonate) bound by electrostatic forces inside the PhoE ionic channel of the Escherichia coli outer membrane [15].

Biological context of ECs0268

• DNA sequence analysis revealed the following substitutions in the 330-residue-long PhoE protein: Arg-201----His (three isolates), Arg-201----Cys, Gly-238----Ser, Gly-275----Ser and Gly-275----Asp [16].
• When the corresponding fragment of the Salmonella typhimurium chromosome was transferred to E. coli K-12 using an RP4::miniMu plasmid, pULB113, no production of S. typhimurium PhoE could be detected [17].
• Osmoregulation of PhoE operated independently of the activity of the PhoR phosphate sensor and did not involve cross-talk from the homologous osmosensor EnvZ [18].
• For OmpF, OmpC, and PhoE porins it is shown that, contrary to current dogma, the genes can be overexpressed without undue deleterious effects upon cell growth and are stable, even under conditions of continuous expression [19].
• Inhibition of PhoE translocation across Escherichia coli inner-membrane vesicles by synthetic signal peptides suggests an important role of acidic phospholipids in protein translocation [20].

Anatomical context of ECs0268

• The assembly of the in vitro synthesized outer membrane protein PhoE into purified outer membranes was investigated [11].
• The structural model of the PhoE monomer consists of a flattened cylinder with a large water-filled vestibule about 35 A long with an elliptically shaped opening that is 27 A along the major axis and 18 A along the minor axis [13].
• These results show that, except for the signal sequence, there is no specific sequence within the PhoE protein that is essential for transport through the cytoplasmic membrane [21].
• We have now shown for the first time that PhoE can also be used as a carrier molecule for T cell epitopes [5].
• A carrier system was developed to analyze in vitro whether foreign T cell epitopes, inserted in the outer membrane protein PhoE of Escherichia coli and expressed by recombinant bacteria, are efficiently processed and presented via human leukocyte antigen (HLA) class I and II molecules by bacterial infected human macrophages [22].

Associations of ECs0268 with chemical compounds

• Furthermore, the efficiency of correct assembly of PhoE was greatly reduced when outer membranes of deep rough lipopolysaccharide mutants were used, indicating an important role of lipopolysaccharides in the assembly of the porin [11].
• The results are consistent with the assumption that the charge spot in PhoE consists of only 1 lysine per monomer, located in position 125 of the primary sequence and probably close to the pore interior [23].
• Apparently, Triton X-100 induces an assembly-competent state in the PhoE protein with a very short half-life [11].
• The looped precursor competed with translocation of wild type precursor PhoE, and looped precursor that was first bound to inner membrane vesicles could be translocated after the addition of dithiothreitol [24].
• In vivo, no drastic differences in the translocation kinetics were observed as compared with wild-type PhoE, except when a charged residue (Arg) was substituted for Gly -10 [25].

Analytical, diagnostic and therapeutic context of ECs0268

• OmpC and PhoE porins of Escherichia coli were examined by the patch-clamp technique following reconstitution in liposomes, and were observed primarily in the open (conducting) state [8].
• Thus, it appears that: (i) data on the localization of hybrid proteins merely based on cell fractionation experiments are not reliable, and (ii) either the C-terminal 15% of PhoE protein contain information which is essential for transport, or PhoE-LacZ hybrid proteins can never be transported out of the cytoplasm [26].
• Western blot analyses of cell extracts with anti-TolA antibodies indicated that TolA forms high molecular weight complexes specifically with trimeric OmpF, OmpC, PhoE and LamB, but not with OmpA [27].
• The folding of in vitro synthesized outer membrane protein PhoE of Escherichia coli was studied in immunoprecipitation experiments with monoclonal antibodies which recognize cell surface-exposed conformational epitopes [28].
• The behavior of the chemically synthesized PhoE signal peptide and signal peptide fragments on hydrophilic-hydrophobic interfaces was studied with circular dichroism and monolayer techniques [29].

References