Molecular Mechanisms of Alamethicin Channel Gating

Quay, Steven C.; Latorre, Ramon

doi:10.1016/s0006-3495(82)84648-1

Cited by 13 publications

(4 citation statements)

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“…While channels are likely to be aggregates of transmembrane helices, other sorts of aggregates could also exist with a variety of conformations and topologies. Similarly, although there is evidence that monomeric alamethicin in membranes is predominantly surface-associated (Huang &Wu,1991),a dynamic ensemble of monomer conformations and topologies presumably also exists (Quay & Latorre, 1981;Vogel, 1987).…”

Section: Discussionmentioning

confidence: 99%

Alamethicin Pyromellitate: An Ion-Activated Channel-Forming Peptide

Woolley¹,

Epand²,

Kerr³

et al. 1994

Biochemistry

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The synthesis and characterization of alamethicin pyromellitate (Alm-PM), a derivative of the channel-forming peptide alamethicin bearing three negative charges at the C-terminus, is described. The self-association of Alm-PM in small unilamellar vesicles of dioleoylphosphatidylcholine (DOPC), monitored using circular dichroism (CD) spectroscopy, occurs much less readily than the self-association of unmodified alamethicin. Channel formation by Alm-PM also occurs less readily and exhibits a higher voltage threshold for activation in planar lipid bilayers and in lipid vesicles. An increase in the salt concentration, and particularly the addition of calcium ions, promotes Alm-PM self-association as monitored by CD spectroscopy. Calcium also facilitates channel formation by Alm-PM both in planar lipid bilayers and in lipid vesicles by lowering the voltage threshold for activation. Thus Alm-PM behaves as an ion-activated ion channel. These results indicate that the self-association of alamethicin-like peptides in membranes is critical for channel formation and that transmembrane flip-flop of peptide helices is not required. In addition, these results demonstrate that the activity of channel-forming peptides may be controlled by controlling the process of self-association.

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Section: Discussionmentioning

confidence: 99%

Alamethicin Pyromellitate: An Ion-Activated Channel-Forming Peptide

Woolley¹,

Epand²,

Kerr³

et al. 1994

Biochemistry

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“…A suggested functional role of the membrane potential in the induction of new conformational states of polypeptide chains within the membrane is provided by studies ofan eicosapeptide, alamethicin, which forms voltage-dependent channels in phospholipid bilayer membranes (25). In addition, Blumenthal et aL (26) have demonstrated a voltage-dependent translocation of asialoglycoprotein receptors in lipid bilayers, and Donovan et al (27) have shown that diphtheria toxin forms voltage-dependent, anion-selective channels.…”

Section: Discussionmentioning

confidence: 99%

Role for membrane potential in the secretion of protein into the periplasm of Escherichia coli.

Daniels¹,

Bole²,

Quay³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

156

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The leucine-specific binding protein of Eschewchia coli is a.periplasmic protein that.is synthesized as a precursor and subsequently is processed during its secretion into the periplasmic space. The processing of both -the leucine-specific binding.protein and a plasmid-coded (-lactamase is inhibited by phenethyl alcohol and by the proton ionophore, carbonylcyanide m-chlorophenylhydrazone (CCCP). The levels of CCCP that inhibit processing also produce significant decreases in the membrane potential. Valinomycin, a potassium ionophore, also inhibits processing of the leucine'specific binding protein in spheroplasts. Processing can 'be restored in' CCCP-treated cells and in valinomycin-treated~spherqplasts by dilution ofthe treated cells in fresh medium. These results suggest a role for membrane potential in the secretion of periplasmic proteins. A model is presented which suggests .that membrane potential plays a primary role in the proper orientation of the precursor signal sequence within the membrane, thus promoting processing and;secretion.Escherichia coli periplasmic proteins are synthesized on membrane-bound ribosomes in precursor forms with an NH2-terminal amino acid sequence (signal sequence) and subsequently are processed and secreted through the inner membrane (1,'2). During the secretory process, the signal sequence (3) is cleaved by a leader peptidase (4). We have' shown that the leucine-spe-.cific binding protein, 'which is a periplasmic component of a leucine transport system.in E. coli, is synthesized as a precursor that contains a 23-amino acid signal sequence (5). Using pulse-chase. experiments with intact cells, we recently have found.that the precursor of the leucine-specific. binding protein can be processed after translation (unpublished data). Although the structure of a number of signal sequences have been determined (6), the mechanism of membrane translocation of the nascent protein is not understood. A role for membrane potential has been implicated for the proper insertion and processing of the M13 precoat protein within the cytoplasmic membrane (7,8). In this report, we demonstrate a requirement for a membrane,potential in the processing and secretion of two E. coli periplasmic proteins, the leucine-specific binding protein and ,(3lactamase. During the preparation of this manuscript, we learned of studies in Linda Randall's laboratory showing that the export ofseveral E. coli outer membrane proteins (products of ompF, ompA, and lamB genes) and the periplasmic binding proteins for maltose and arabinose also require a meembrane potential (9, 10). METHODS CCCP Treatment. The E. coli strains, AE191, (IstR, livj, IivP9, arg, his, trp, thy, leu) and the Hfr Hayes Alon strain (P. Bassford collection) were used in these experiments. These strains were transformed (11) with the hybrid plasmid pOX7 (5), which carries the livK gene coding for the leucine-specific binding protein and the bla gene for f-lactamase. These transformed strains were grown in 4-morpholinepropanesulfonic acid (Mops...

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“…These channels consist in aggregates of amphipathic (mostly o~-) helical monomers whose sequential uptake and release (the 'barrelstave' model) leads to the multi-level singleconductance pattern [1,2]. According to the model now in favour [3], at rest, the N-terminal part up to Pro 14 is within the membrane [4], without crossing it totally, whilst the remainder of the molecule lies at the interface. The electric field acting on the peptide dipole would align the two parts Correspondence address: G. Molle, Polym6res, Biopolym6res et Membranes, UA 500 CNRS, Facult6 des Sciences de Rouen, BP 118, 76134 Mont Saint Aignan Cedex, France of the molecule and, drawing the N-terminal towards the opposite interface, would create a pore by the association of several of these monomers.…”

Section: Introductionmentioning

confidence: 99%

Voltage‐dependent and multi‐state ionic channels induced by trichorzianines, anti‐fungal peptides related to alamethicin

1987

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The ionophore properties of two peptaibols of the trichorzianine family have been investigated in planar lipid bilayers and compared to those of alamethicin. Macroscopic conductance experiments reveal voltagedependent channels only in the thinnest membranes and a greater efficiency of the neutral analog. In singlechannel experiments, a multi-state behaviour, consistent with the usual barrel-stave model, is disclosed but the discrete current fluctuations are much more rapid than for alamethicin. The results indicate a stringent requirement for the helix length/bilayer thickness match in agreement with a previous model and suggest the design of new synthetic peptides.

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Molecular Mechanisms of Alamethicin Channel Gating

Cited by 13 publications

References 1 publication

Alamethicin Pyromellitate: An Ion-Activated Channel-Forming Peptide

Alamethicin Pyromellitate: An Ion-Activated Channel-Forming Peptide

Role for membrane potential in the secretion of protein into the periplasm of Escherichia coli.

Voltage‐dependent and multi‐state ionic channels induced by trichorzianines, anti‐fungal peptides related to alamethicin

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