Voltage-gating of Escherichia coli porin: a cystine-scanning mutagenesis study of loop 3 1 1Edited by I. B. Holland

Bainbridge, G.R.; Mobasheri, Hamid; Armstrong, Geoffrey A.; Lea, E.J.A.; Lakey, Jeremy H.

doi:10.1006/jmbi.1997.1474

Cited by 63 publications

(75 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1B). Analogous results have been reported for the bacterial porin, OmpF (35), where a series of Cys mutations were generated between residues in the constriction loop and the wall of the ␤-barrel in which no alterations in voltage gating were observed upon cross-linking.…”

Section: Journal Of Biological Chemistry 11441supporting

confidence: 77%

See 1 more Smart Citation

Affixing N-terminal α-Helix to the Wall of the Voltage-dependent Anion Channel Does Not Prevent Its Voltage Gating

Teijido

Ujwal

Hillerdal

et al. 2012

Journal of Biological Chemistry

View full text Add to dashboard Cite

Background: There is ongoing controversy concerning the location and mobility of the N-terminal ␣-helix in VDAC1 during voltage gating. Results: mVDAC1 with the N-terminal ␣-helix cross-linked to ␤-strand 11 forms typical voltage-gated channels. Conclusion:The N-terminal domain of VDAC1 does not move independently during voltage gating. Significance: This study dramatically alters the current view of voltage gating dynamic in VDAC1.The voltage-dependent anion channel (VDAC) governs the free exchange of ions and metabolites between the mitochondria and the rest of the cell. The three-dimensional structure of VDAC1 reveals a channel formed by 19 ␤-strands and an N-terminal ␣-helix located near the midpoint of the pore. The position of this ␣-helix causes a narrowing of the cavity, but ample space for metabolite passage remains. The participation of the N-terminus of VDAC1 in the voltage-gating process has been well established, but the molecular mechanism continues to be debated; however, the majority of models entail large conformational changes of this N-terminal segment. Here we report that the pore-lining N-terminal ␣-helix does not undergo independent structural rearrangements during channel gating. We engineered a double Cys mutant in murine VDAC1 that cross-links the ␣-helix to the wall of the ␤-barrel pore and reconstituted the modified protein into planar lipid bilayers. The modified murine VDAC1 exhibited typical voltage gating. These results suggest that the N-terminal ␣-helix is located inside the pore of VDAC in the open state and remains associated with ␤-strand 11 of the pore wall during voltage gating.The voltage-dependent anion channel (VDAC) 4 serves as the primary conduit between the mitochondria and the rest of the cell, facilitating free exchange of ions and metabolites across the outer mitochondrial membrane. In addition to its metabolic and energetic functions, VDAC has a more complex role, serving as a receptor for molecules and proteins that modulate the organelle's permeability and thereby its function (1-3). This multifunctional channel has been implicated in the metabolic stresses of cancer, cardiovascular disease, and mitochondrialdependent cell death (4 -8); thus, understanding the structure and function of VDAC constitutes a critical objective for basic as well as medical research.Single channel conductance experiments on VDAC1 at low membrane potential (Ͻ30 mV) reveal a high conductance (4.1 Ϯ 0.1 nanosiemens in 1 M KCl) indicative of a large pore, usually referred to as the "open" state of the channel (1). This conformer facilitates the passage of 10 6 ATP molecules (9) and displays a preference for monovalent anions over cations with the anion-to-cation permeability ratio of 2:1 in high salt (10) and 4:1 in physiological salt concentration (11). As voltage is increased (Ͼ30 mV) in either a positive or a negative direction, the channel switches into the lower conducting states (around 2 nanosiemens in 1 M KCl), termed as the "closed" state(s). These states are cation-selective wi...

show abstract

Section: Journal Of Biological Chemistry 11441supporting

confidence: 77%

“…2A), and TMRM accessibility was restored. Similar features have been observed in other outer membrane proteins that exhibited cross-linking (34,35). …”

supporting

confidence: 84%

Affixing N-terminal α-Helix to the Wall of the Voltage-dependent Anion Channel Does Not Prevent Its Voltage Gating

Teijido

Ujwal

Hillerdal

et al. 2012

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Therefore, the movement of the loop containing the acidic residues in response to voltage is in principle possible, as shown by theoretical analysis (710). However, when the loop was fixed to the barrel wall by a disulfide bond, the gating still occurred (29,194,492), a result that rules out at least a largescale movement of the loop against the barrel wall. Small movements in parts of the loop are still possible, and some molecular dynamics simulation studies (628,659) indeed seem to support this idea.…”

Section: Classical Porinsmentioning

confidence: 99%

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Nikaido

2003

Microbiol Mol Biol Rev

3,768

3,800

View full text Add to dashboard Cite

Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions

show abstract

“…Within each pore a long polypeptide loop (L3) runs along one side of the barrel wall and narrows the pore to create an "eyelet" region (5,8,19). Across this region, these porins have a strong transverse electric field generated by basic residues in the barrel wall and acidic residues and peptide carbonyl groups on L3 (8,17).…”

Section: Ferrooxidans Major Outer Membrane Protein 2321mentioning

confidence: 99%

“…The permeability is determined not only by the size of the penetrating molecule but also by its charges, which have to be oriented within the transverse electric field in the constriction zone (5,17). Changes in the pore size have been reported when amino acids of the PEFGG sequence present in loop L3, which is highly conserved in the superfamily of bacterial porins (15) are replaced by mutation (5,12). For example, the change of glutamic acid for cysteine altered the permeability of some charged molecules (12).…”

Section: Ferrooxidans Major Outer Membrane Protein 2321mentioning

confidence: 99%

Molecular Cloning, Sequencing, and Expression of omp-40 , the Gene Coding for the Major Outer Membrane Protein from the Acidophilic Bacterium Thiobacillus ferrooxidans

Guiliani

Jerez

2000

Appl Environ Microbiol

View full text Add to dashboard Cite

Thiobacillus ferrooxidans is one of the chemolithoautotrophic bacteria important in industrial biomining operations. Some of the surface components of this microorganism are probably involved in adaptation to their acidic environment and in bacterium-mineral interactions. We have isolated and characterized omp40, the gene coding for the major outer membrane protein from T. ferrooxidans. The deduced amino acid sequence of the Omp40 protein has 382 amino acids and a calculated molecular weight of 40,095.7. Omp40 forms an oligomeric structure of about 120 kDa that dissociates into the monomer (40 kDa) by heating in the presence of sodium dodecyl sulfate. The degree of identity of Omp40 amino acid sequence to porins from enterobacteria was only 22%. Nevertheless, multiple alignments of this sequence with those from several OmpC porins showed several important features conserved in the T. ferrooxidans surface protein, such as the approximate locations of 16 transmembrane beta strands, eight loops, including a large external L3 loop, and eight turns which allowed us to propose a putative 16-stranded beta-barrel porin structure for the protein. These results together with the previously known capacity of Omp40 to form ion channels in planar lipid bilayers strongly support its role as a porin in this chemolithoautotrophic acidophilic microorganism. Some characteristics of the Omp40 protein, such as the presence of a putative L3 loop with an estimated isoelectric point of 7.21 allow us to speculate that this can be the result of an adaptation of the acidophilic T. ferrooxidans to prevent free movement of protons across its outer membrane.

show abstract

Voltage-gating of Escherichia coli porin: a cystine-scanning mutagenesis study of loop 3 1 1Edited by I. B. Holland

Cited by 63 publications

References 35 publications

Affixing N-terminal α-Helix to the Wall of the Voltage-dependent Anion Channel Does Not Prevent Its Voltage Gating

Affixing N-terminal α-Helix to the Wall of the Voltage-dependent Anion Channel Does Not Prevent Its Voltage Gating

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Molecular Cloning, Sequencing, and Expression of omp-40 , the Gene Coding for the Major Outer Membrane Protein from the Acidophilic Bacterium Thiobacillus ferrooxidans

Contact Info

Product

Resources

About