Probing alamethicin channels with water-soluble polymers. Effect on conductance of channel states

Bezrukov, Sergey M.; Vodyanoy, Igor

doi:10.1016/s0006-3495(93)81336-5

Cited by 196 publications

(224 citation statements)

References 24 publications

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“…It is found that their presence both decreases solution conductivity and increases the effective ion concentration in PEG free regions, consistent with previous studies (9,24,25). In the relevant regime of salt concentrations (≤1 M) we do not observe any neutral vs. polyelectrolyte behavior of PEG (Supporting Information, Effect of Electrolytes).…”

Section: Discussionsupporting

confidence: 91%

Size-dependent forced PEG partitioning into channels: VDAC, OmpC, and α-hemolysin

Aksoyoglu

Podgornik

Bezrukov

et al. 2016

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

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Nonideal polymer mixtures of PEGs of different molecular weights partition differently into nanosize protein channels. Here, we assess the validity of the recently proposed theoretical approach of forced partitioning for three structurally different β-barrel channels: voltage-dependent anion channel from outer mitochondrial membrane VDAC, bacterial porin OmpC (outer membrane protein C), and bacterial channel-forming toxin α-hemolysin. Our interpretation is based on the idea that relatively less-penetrating polymers push the more easily penetrating ones into nanosize channels in excess of their bath concentration. Comparison of the theory with experiments is excellent for VDAC. Polymer partitioning data for the other two channels are consistent with theory if additional assumptions regarding the energy penalty of pore penetration are included. The obtained results demonstrate that the general concept of "polymers pushing polymers" is helpful in understanding and quantification of concrete examples of size-dependent forced partitioning of polymers into protein nanopores.β-barrel pores | nanopore-based sensing | polymer confinement | polymer transport | macromolecular crowding P artitioning of polymers into nanosize cavities has broad relevance (1), generally in biology, where the consequences of molecular crowding are well appreciated but not completely understood (2, 3), and in biotechnology for single-molecule sensing and characterization based on the variation of current through ion-conducting aqueous pores (4-7). The partitioning of nonionic polymers such as PEG into α-hemolysin (aHL) from Staphylococcus aureus has been previously studied and shown to be size-dependent at relatively low salt concentrations (8-13). In a different way, namely, as the amplitude of channel blockage, polymer size dependency has also been observed in single-molecule studies at high salt concentrations (4 M KCl) with aHL (14) and recently with aerolysin from Aeromonas hydrophila (15), and was shown to exhibit pronounced size sensitivity with resolution in the submonomer range.We studied passive size-dependent partitioning and size discrimination that can be manipulated to force polymers into nanosize pores under strong nonideality, when polymer partitioning is qualitatively modified by polymer-polymer repulsion that allows polymers, which are excluded in dilute solutions, to enter the channel pore (13). This concentration-dependent partitioning was rationalized by an argument that the overlap concentration of the polymer in the pore is higher than that in the bath (16,17). For polymer mixtures, where one component is used to preferentially push another into a cavity, this phenomenon of forced polymer partitioning was referred to as "polymers pushing polymers" (PPP) (18). Using the osmotic pressure of a polymer solution composed of various sizes of the same type of polymers, these theoretical advances quantified the forced preferential entry of polymers into a nanopore depending on their size and the pore penetration energy penalty. T...

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Section: Discussionsupporting

confidence: 91%

Size-dependent forced PEG partitioning into channels: VDAC, OmpC, and α-hemolysin

Aksoyoglu

Podgornik

Bezrukov

et al. 2016

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

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“…5C we obtained 12 and 16 Å for the diameters of 60-and 600-pS channels, respectively. The estimated diameter of the 60-pS channel is close to the diameter of the alamethicin channel, 12.6 Å, in its lowest conductance state (76).…”

Section: Estimation Of the Size Of 60-and 600-ps Channelsmentioning

confidence: 57%

Lipid Dependence of the Channel Properties of a Colicin E1-Lipid Toroidal Pore

Sobko

Kotova

Antonenko

et al. 2006

Journal of Biological Chemistry

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Colicin E1 belongs to a group of bacteriocins whose cytotoxicity toward Escherichia coli is exerted through formation of ion channels that depolarize the cytoplasmic membrane. The lipid dependence of colicin single-channel conductance demonstrated intimate involvement of lipid in the structure of this channel. The colicin formed "small" conductance 60-picosiemens (pS) channels, with properties similar to those previously characterized, in 1,2-dieicosenoyl-snglycero-3-phosphocholine (C20) or thinner membranes, whereas it formed a novel "large" conductance 600-pS state in thicker 1,2-dierucoyl-sn-glycero-3-phosphocholine (C22) bilayers. Both channel states were anion-selective and voltage-gated and displayed a requirement for acidic pH. Lipids having negative spontaneous curvature inhibited the formation of both channels but increased the ratio of open 600 pS to 60 pS conductance states. Different diameters of small and large channels, 12 and 16 Å , were determined from the dependence of single-channel conductance on the size of nonelectrolyte solute probes. Colicin-induced lipid "flip-flop" and the decrease in anion selectivity of the channel in the presence of negatively charged lipids implied a significant contribution of lipid to the structure of the channel, most readily described as toroidal organization of lipid and protein to form the channel pore.The lipid environment of membrane proteins that defines the local distribution of polarity, dielectric constant, and steric geometry has a central role in the determination of protein structure and function. For ion channels, lipids impose the following constraints: (i) structure-function is sensitive to the matching of hydrophobic thickness of the protein and lipid bilayer (1-10); (ii) opening of channels (e.g. mechano-sensitive, can be dependent on bilayer tension) (11), which manifests itself in a dependence on acyl chain length (12); (iii) spontaneous curvature (SC) 2 of lipids linked to the lateral pressure of the bilayer can modulate ion channel activity (13), as demonstrated for the KcsA channel (14) and mechano-sensitive MscL channels (12, 15); and (iv) many channel proteins require anionic lipids for function (16 -19).Channel-forming proteins can require specific lipids, presumably because of a combination of charge and curvature parameters, to form active channels (e.g. anionic lipid bound between the transmembrane ␣-helices and necessary for gating of the KcsA channel (20, 21)). The lantibiotic nisin provides a well defined example of lipid participation in peptide pore formation, in which the peptidoglycan precursor lipid II is an intrinsic component of the pore formed by this antimicrobial peptide (22). The proposed structure of this pore contains 5-8 nisin molecules and an identical number of lipid II molecules (23). Participation of lipid in the formation of a channel wall was hypothesized for cholesteroldependent cytolysins (24,25).Colicins are plasmid-encoded bacteriocins that are cytotoxic to Escherichia coli and related strains. Their modes of ...

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“…Bilayer membranes were formed from monolayers as described previously (32). Prior to membrane formation, the orifices in the Teflon film separating reconstitution cell compartments were pretreated either with a suspension of petroleum jelly in petroleum ether (42) or with a 1% solution of hexadecane in pentane (43). Both approaches ensured formation of stable and virtually nonconductive planar membranes.…”

Section: Methodsmentioning

confidence: 99%

Membrane Lipid Composition Regulates Tubulin Interaction with Mitochondrial Voltage-dependent Anion Channel

Rostovtseva

Gurnev

Chen

et al. 2012

Journal of Biological Chemistry

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Background: Dimeric ␣␤-tubulin regulates mitochondrial respiration by blocking VDAC. Results: The on-rate of tubulin binding to VDAC varies more than 100-fold depending on the lipid type. Conclusion: VDAC blockage by tubulin involves a crucial step of tubulin interaction with the membrane. Significance: VDAC-tubulin binding is a new example of lipid-controlled protein-protein interactions that contribute to mitochondrial metabolism regulation.

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Probing alamethicin channels with water-soluble polymers. Effect on conductance of channel states

Cited by 196 publications

References 24 publications

Size-dependent forced PEG partitioning into channels: VDAC, OmpC, and α-hemolysin

Size-dependent forced PEG partitioning into channels: VDAC, OmpC, and α-hemolysin

Lipid Dependence of the Channel Properties of a Colicin E1-Lipid Toroidal Pore

Membrane Lipid Composition Regulates Tubulin Interaction with Mitochondrial Voltage-dependent Anion Channel

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