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  • 1
    Electronic Resource
    Electronic Resource
    Ursache und Bedingungen (1913)
    Springer
    Naturwissenschaften 1 (1913), S. 360-361 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01802073
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  • 2
    Electronic Resource
    Electronic Resource
    Structure-function relationships in diphtheria toxin channels: III. Residues which affect the cis pH dependence of channel conductance (1994)
    Springer
    The journal of membrane biology 137 (1994), S. 45-57 
    Details
    ISSN: 1432-1424
    Keywords: Diphtheria toxin ; Site-directed mutagenesis ; Planar lipid bilayers ; Single channel conductance ; Ion selectivity ; pH dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The conductance of channels formed by diphtheria toxin (DT) in lipid bilayer membranes depends strongly on pH. We have previously shown that a 61 amino acid region of the protein, denoted TH8-9, is sufficient to form channels having the same pH-dependent conductance properties as those of whole toxin channels. One residue in this region, Aspartate 352, is responsible for all the dependence of single channel conductance on trans pH, whereas another, Glutamate 349, has no effect. Here, we report that of the seven remaining charged residues in the TH8-9 region, mutations altering the charge on H322, H323, H372, and R377 have minimal effects on single channel conductance; mutations of Glutamates 326, 327, or 362, however, significantly affect single channel conductance as well as its dependence on cis pH. Moreover, Glutamate 362 is titratable from both the cis and trans sides of the membrane, suggesting that this residue lies within the channel; it is more accessible, however, to cis than to trans protons. These results are consistent with the membrane-spanning topology previously proposed for the TH8-9 region, and suggest a geometric model for the DT channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234997
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  • 3
    Electronic Resource
    Electronic Resource
    Transmembrane Insertion of the Colicin Ia Hydrophobic Hairpin (1997)
    Springer
    The journal of membrane biology 157 (1997), S. 27 -37 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Streptavidin — Biotin — Channel — Voltage dependence — Bilayer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Colicin Ia is a bactericidal protein that forms voltage-dependent, ion-conducting channels, both in the inner membrane of target bacteria and in planar bilayer membranes. Its amino acid sequence is rich in charged residues, except for a hydrophobic segment of 40 residues near the carboxyl terminus. In the crystal structure of colicin Ia and related colicins, this segment forms an α-helical hairpin. The hydrophobic segment is thought to be involved in the initial association of the colicin with the membrane and in the formation of the channel, but various orientations of the hairpin with respect to the membrane have been proposed. To address this issue, we attached biotin to a residue at the tip of the hydrophobic hairpin, and then probed its location with the biotin-binding protein streptavidin, added to one side or the other of a planar bilayer. Streptavidin added to the same side as the colicin prevented channel opening. Prior addition of streptavidin to the opposite side protected channels from this effect, and also increased the rate of channel opening; it produced these effects even before the first opening of the channels. These results suggest a model of membrane association in which the colicin first binds with the hydrophobic hairpin parallel to the membrane; next the hairpin inserts in a transmembrane orientation; and finally the channel opens. We also used streptavidin binding to obtain a stable population of colicin molecules in the membrane, suitable for the quantitative study of voltage-dependent gating. The effective gating charge thus determined is pH-independent and relatively small, compared with previous results for wild-type colicin Ia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900213
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of Mutations in Proline 345 on Insertion of Diphtheria Toxin into Model Membranes (1999)
    Springer
    The journal of membrane biology 167 (1999), S. 173-181 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Diphtheria toxin — Proline — Mutagenesis — Membrane insertion — Transmembrane domain — Site-specific labeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Translocation of the catalytic domain of diphtheria toxin (DT) across the endosomal membrane to the cytoplasm of mammalian cells requires the low-pH-dependent insertion of a hydrophobic helical hairpin (TH8-TH9) that is buried within the T domain of the native protein. Mutations of Pro345, which terminates helix TH8, have been reported to block toxicity for Vero cells. We found that mutant toxins in which Pro345 had been replaced by Cys, Glu, or Gly were profoundly defective at low pH in forming channels in planar phospholipid bilayers and in permeabilizing phospholipid vesicles to entrapped fluorophores. Experiments with isolated T domain containing a polarity-sensitive fluorophore attached to Cys at position 332 suggest that the P345E mutation blocks membrane insertion. None of the Pro345 mutations shifted the pH-dependence of binding in solution of the hydrophobic fluorophore, 2-p-toluidinyl-naphthalene 7-sulfonate. The results indicate that proline at position 345 is required for the T domain to insert into phospholipid bilayers or to adopt a functional conformation within the bilayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900481
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  • 5
    Electronic Resource
    Electronic Resource
    Structure function relationships in diphtheria toxin channels: II. A residue responsible for the channel's dependence on trans pH (1994)
    Springer
    The journal of membrane biology 137 (1994), S. 29-44 
    Details
    ISSN: 1432-1424
    Keywords: Diphtheria toxin ; Site-directed mutagenesis ; Planar lipid bilayers ; Single channel conductance ; Ion selectivity ; pH dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Ion-conducting channels formed in lipid bilayers by diphtheria toxin are highly pH dependent. Among other properties, the channel's single channel conductance and selectivity depend on proton concentrations on either side of the membrane. We have previously shown that a 61 amino acid fragment of DT is sufficient to form a channel having the same pH-dependent single channel properties as that of the intact toxin. This region corresponds to an a-helical hairpin in the recently published crystal structure of DT in solution; the hairpin contains two α-helices, each long enough to span a membrane, connected by a loop of about nine residues. This paper reports on the single channel effects of mutations which alter the two negatively charged residues in this loop. Changing Glutamate 349 to neutral glutamine or to positive lysine has no effect on the DT channel's single channel conductance or selectivity. In contrast, mutations of Aspartate 352 to neutral asparagine (DT-D352N) or positive lysine (DT-D352K) cause progressive reductions in single channel conductance at pH 5.3 cis/7.2 trans (in 1 m KCl), consistent with this group interacting electrostatically with ions in the channel. The cation selectivity of these mutant channels is also reduced from that of wild-type channels, a direction consistent with residue 352 influencing permeant ions via electrostatic forces. When both sides of the membrane are at pH 4, the conductance difference between wild-type and DT-D352N channels is minimal, suggesting that Asp 352 (in the wild type) is neutral at this pH. Differences observed between wild-type and DT-D352N channels at pH 4.0 cis/7.2 trans (with a high concentration of permeant buffer in the cis compartment) imply that residue 352 is on or near the trans side of the membrane. Comparing the conductances of wild-type and DT-D352K channels at large (cis) positive voltages supports this conclusion. The trans location of position 352 severely constrains the number of possible membrane topologies for this region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234996
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  • 6
    Electronic Resource
    Electronic Resource
    Structure-function relationships in diphtheria toxin channels: I. Determining a minimal channel-forming domain (1994)
    Springer
    The journal of membrane biology 137 (1994), S. 17-28 
    Details
    ISSN: 1432-1424
    Keywords: Diphtheria toxin ; Site-directed mutagenesis ; Planar lipid bilayers ; Ion channels ; T-domain ; Channel-forming peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Diphtheria Toxin (DT) is a 535 amino acid exotoxin, whose active form consists of two polypeptide chains linked by an interchain disulphide bond. DT's N-terminal A fragment kills cells by enzymatically inactivating their protein synthetic machinery; its C terminal B chain is required for the binding of toxin to sensitive cells and for the translocation of the A fragment into the cytosol. This B fragment, consisting of its N-terminal T domain (amino acids 191–386) and its C-terminal R domain (amino acids 387–535) is responsible for the ion-conducting channels formed by DT in lipid bilayers and cellular plasma membranes. To further delineate the channel-forming region of DT, we studied channels formed by deletion mutants of DT in lipid bilayer membranes under several pH conditions. Channels formed by mutants containing only the T domain (i.e., lacking the A fragment and/or the R domain), as well as those formed by mutants replacing the R domain with Interleukin-2 (Il–2), have single channel conductances and selectivities essentially identical to those of channels formed by wild-type DT. Furthermore, deleting the N-terminal 118 amino acids of the T domain also has minimal effect on the single channel conductance and selectivity of the mutant channels. Together, these data identify a 61 amino acid stretch of the T domain, corresponding to the region which includes α-helices TH8 and TH9 in the crystal structure of DT, as the channel-forming region of the toxin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234995
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical Excitability of Isolated Frog Skin (1961)
    [s.l.] : Nature Publishing Group
    Nature 190 (1961), S. 1119-1120 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The abdominal skin of the frog Rana pipiens was removed and immediately mounted between two cylindrical 'Lucite' compartments, 6-5 cm. long, 1-15 cm.2 cross-sectional area. There were holes at the far end of each compartment for the silver/silver chloride stimulating electrodes, and at each end ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1901119a0
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  • 8
    Electronic Resource
    Electronic Resource
    A hydroxide ion carrier in planar phospholipid bilayer membranes: (C"6F"5)"2Hg (dipentafluorophenylmercury)
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 946 (1988), S. 221-226 
    Details
    ISSN: 0005-2736
    Keywords: Hydroxide carrier ; Lipid bilayer ; Mercury ; Proton carrier
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0005-2736(88)90396-3
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  • 9
    Electronic Resource
    Electronic Resource
    Mode of action of colicin Ib Formation of ion-permeable membrane channels
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 645 (1981), S. 137-142 
    Details
    ISSN: 0005-2736
    Keywords: (E. coli, Planar bilayer, Vesicle) ; Colicin Ib ; Ion channel ; Ion permeability ; Membrane potential
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(81)90521-6
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  • 10
    Electronic Resource
    Electronic Resource
    Production of Human RAP30 and RAP74 in Bacterial Cells
    Amsterdam : Elsevier
    Protein Expression and Purification 4 (1993), S. 207-214 
    Details
    ISSN: 1046-5928
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1006/prep.1993.1027
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