Models for the structure of outer-membrane proteins of Escherichia coli derived from raman spectroscopy and prediction methods

Vogel, Horst; Jähnig, Fritz

doi:10.1016/0022-2836(86)90292-5

Cited by 350 publications

(203 citation statements)

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“…It is possible that a portion of the OmpA C terminus (including some of the proposed transmembrane segments) may adopt an a-helical conformation and be located inside the porin channel, at least in porins with closed channels. This hypothesis is consistent with predictions for a-helical content in the C-terminal domain made on the basis of Raman spectroscopy (Vogel & Jahnig, 1986) and computer methods (Jeanteur et al, 1994;Koebnik, 1995) and may explain why the N-terminal eight-stranded domain can exist alone in the membrane in a stable conformation (Ried et al, 1994). Transmembrane segments M9, MI I , and MI5 are suitable candidates for folding into an a-helical conformation and residing inside the @-barrel channel.…”

Section: Stathopoulossupporting

confidence: 83%

“…In an attempt to correlate immunologic, biochemical, and genetic data derived from studies on proteins of the OmpA family with the three computer predictions described above, I constructed a new OmpA model. More specifically, this model was based on (1) OmpA topology data from previous studies (Chen et al, 1980;Braun & Cole, 1984;Morona et al, 1984Morona et al, , 1985Vogel & Jahnig, 1986;Freudl, 1989;Ried et al, 1994;Ruppert et al, 1994); (2) the OmpA structure predictions of Jeanteur et al,Schirmer and Cowan,and Ferenci;(3) topological information from studies on the OprF C-terminal region (Wong et al, 1993;Rawling et al, 1995); and (4) two recent reports (De Mot & Vanderleyden, 1994;Koebnik, 1995) that identified conserved residues and a common sequence motif between OmpA-related outer membrane proteins and MotB, a peptidoglycan-associated protein of gram-positive bacteria. OmpA residues involved in direct interaction with peptidoglycan are expected to lie on the periplasmic side of the membrane.…”

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confidence: 99%

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An alternative topological model for Escherichia coli OmpA

Stathopoulos

1996

Protein Science

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Abstract:The current topological model for the Escherichia coli outer membrane protein OmpA predicts eight N-terminal transmembrane segments followed by a long periplasmic tail. Several recent reports have raised serious doubts about the accuracy of this prediction. An alternative OmpA model has been constructed using (1) computer-aided predictions developed specifically to predict topology of bacterial outer membrane porins, (2) the results of two reports that identified sequence homologies between OmpA and other peptidoglycan-associated proteins, and (3) biochemical, immunochemical, and genetic topological data on proteins of the OmpA family provided by numerous previous studies. The new model not only agrees with the varied experimental data concerning OmpA but also provides an improved understanding of the relationship between the structure and the multifunctional role of OmpA in the bacterial outer membrane.Keywords: E. coli; OmpA; outer membrane; porin; topology Much information has been published in the last few years regarding the structure of prokaryotic porins, the major protein components of the bacterial outer membrane. The first reported crystal structure of a porin was of that from Rhodobacter cupsulafus (Weiss and Schulz, 1992), and four more porin structures have been reported since: the structures of the Escherichia coli general porins OmpF and PhoE (Cowan et al., 1992) and the specific porin LamB (Schirmer et al., 1995), and the structure of a porin from the phototrophic bacterium Rhodopseudomonas blasfica (Kreusch & Schulz, 1994). These studies have shown that, unlike cytoplasmic membrane proteins, which are rich in a-helical structure, outer membrane proteins primarily consist of inclined amphipathic and antiparallel 0 sheets arranged in a 0-barrel conformation.One of the major proteins of the E. coli outer membrane, OmpA, has been shown to function as an inefficient general porin

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Section: Stathopoulossupporting

confidence: 83%

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confidence: 99%

An alternative topological model for Escherichia coli OmpA

Stathopoulos

1996

Protein Science

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“…A somewhat analogous structure has been proposed for the Escherichia coli outer membrane protein OmpA (5,12,18), and these proteins, which also share some functional similarities, are considered orthologs. Consistent with this concept, significant amino acid sequence similarity has been detected between OprF and OmpA, but only in their C-terminal domains (39% identity, 56% similarity).…”

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confidence: 83%

The Amino Terminus of Pseudomonas aeruginosa Outer Membrane Protein OprF Forms Channels in Lipid Bilayer Membranes: Correlation with a Three-Dimensional Model

2000

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Pseudomonas aeruginosa OprF forms 0.36-nS channels and, rarely, 2-to 5-nS channels in lipid bilayer membranes. We show that a protein comprising only the N-terminal 162-amino-acid domain of OprF formed the smaller, but not the larger, channels in lipid bilayers. Circular dichroism spectroscopy indicated that this protein folds into a ␤-sheet-rich structure, and three-dimensional comparative modeling revealed that it shares significant structural similarity with the amino terminus of the orthologous protein Escherichia coli OmpA, which has been shown to form a ␤-barrel. OprF and OmpA share only 15% identity in this domain, yet these results support the utility of modeling such widely divergent ␤-barrel domains in three dimensions in order to reveal similarities not readily apparent through primary sequence comparisons. The model is used to further hypothesize why porin activity differs for the N-terminal domains of OprF and OmpA.

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“…For example, folded OmpA migrates at 30 kDa, whereas unfolded OmpA migrates at 35 kDa [19]. The 30-kDa form has been shown by Raman, FT-IR and CD spectroscopy [20,22,23,25,27,28], by phage inactivation assays [19] and by single-channel conductivity measurements [29] to correspond to completely folded and functionally active OmpA. The different electrophoretic mobilities of folded and unfolded OmpA have also been used to determine the kinetics of native structure formation with a simple kinetic gel-shift assay, taking advantage of the inhibition of OmpA folding by SDS [23,30,31].…”

Section: In Vitro Requirements For Membrane Protein Foldingmentioning

confidence: 99%

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

Kleinschmidt¹

2003

Cellular and Molecular Life Sciences (CMLS)

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Abstract. The biophysical principles and mechanisms by which membrane proteins insert and fold into a biomembrane have mostly been studied with bacteriorhodopsin and outer membrane protein A (OmpA). This review describes the assembly process of the monomeric outer membrane proteins of Gram-negative bacteria, for which OmpA has served as an example. OmpA is a two-domain outer membrane protein composed of a 171-residue eight-stranded b-barrel transmembrane domain and a 154-residue periplasmic domain. OmpA is translocated in an unstructured form across the cytoplasmic membrane into the periplasm. In the periplasm, unfolded OmpA is kept in solution in complex with the molecular chaperone Skp. After binding of periplasmic lipopolysaccharide, OmpA insertion and folding occur spontaneously upon interaction of the complex with the phospholipid bilayer. Insertion and folding of the b-barrel transmembrane domain into the lipid bilayer are highly synchronized, i.e. the formation of large amounts of b-sheet secondary structure and b-barrel tertiary structure take place in parallel with the same rate constants, while OmpA inserts into the hydrophobic core of the membrane. In vitro, OmpA can successfully fold into a range of model membranes of very different phospholipid compositions, i.e. into bilayers of lipids of different headgroup structures and hydrophobic chain lengths. Three membrane-bound folding intermediates of OmpA were discovered in folding studies with dioleoylphosphatidylcholine bilayers. Their formation was monitored by time-resolved distance determinations by fluorescence quenching, and they were structurally distinguished by the relative positions of the five tryptophan residues of OmpA in projection to the membrane normal. Recent studies indicate a chaperone-assisted, highly synchronized mechanism of secondary and tertiary structure formation upon membrane insertion of b-barrel membrane proteins such as OmpA that involves at least three structurally distinct folding intermediates.

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Models for the structure of outer-membrane proteins of Escherichia coli derived from raman spectroscopy and prediction methods

Cited by 350 publications

References 20 publications

An alternative topological model for Escherichia coli OmpA

An alternative topological model for Escherichia coli OmpA

The Amino Terminus of Pseudomonas aeruginosa Outer Membrane Protein OprF Forms Channels in Lipid Bilayer Membranes: Correlation with a Three-Dimensional Model

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

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