Membrane Permeability of Hydrocarbon-Cross-Linked Peptides (original) (raw)
Related papers
Biochemistry, 2001
The extent of matching of membrane hydrophobic thickness with the hydrophobic length of transmembrane protein segments potentially constitutes a major director of membrane organization. Therefore, the extent of mismatch that can be compensated, and the types of membrane rearrangements that result, can provide valuable insight into membrane functionality. In the present study, a large family of synthetic peptides and lipids is used to investigate a range of mismatch situations. Peptide conformation, orientation, and extent of incorporation are assessed by infrared spectroscopy, tryptophan fluorescence, circular dichroism, and sucrose gradient centrifugation. It is shown that peptide backbone structure is not significantly affected by mismatch, even when the extent of mismatch is large. Instead, this study demonstrates that for tryptophan-flanked peptides the dominant response of a membrane to large mismatch is that the extent of incorporation is reduced, when the peptide is both too short and too long. With increasing mismatch, a smaller fraction of peptide is incorporated into the lipid bilayer, and a larger fraction is present in extramembranous aggregates. Relatively long peptides that remain incorporated in the bilayer have a small tilt angle with respect to the membrane normal. The observed effects depend on the nature of the flanking residues: long tryptophan-flanked peptides do not associate well with thin bilayers, while equisized lysine-flanked peptides associate completely, thus supporting the notion that tryptophan and lysine interact differently with membrane-water interfaces. The different properties that aromatic and charged flanking residues impart on transmembrane protein segments are discussed in relation to protein incorporation in biological systems.
Biophysical Journal, 2007
The membrane peptide pH (low) insertion peptide (pHLIP) lives in three worlds, being soluble in aqueous solution at pH 7.4, binding to the surface of lipid bilayers, and inserting as a transbilayer helix at low pH. With low pH driving the process, pHLIP can translocate cargo molecules attached to its C-terminus via a disulfide and release them in the cytoplasm of a cell. Here we examine a key aspect of the mechanism, showing that pHLIP is monomeric in each of its three major states: soluble in water near neutral pH (state I), bound to the surface of a membrane near neutral pH (state II), and inserted across the membrane as an a-helix at low pH (state III). The peptide does not induce fusion or membrane leakage. The unique properties of pHLIP made it attractive for the biophysical investigation of membrane protein folding in vitro and for the development of a novel class of delivery peptides for the transport of therapeutic and diagnostic agents to acidic tissue sites associated with various pathological processes in vivo.
Membrane Perturbation Induced by Interfacially Adsorbed Peptides
Biophysical Journal, 2004
The structural and energetic characteristics of the interaction between interfacially adsorbed (partially inserted) a-helical, amphipathic peptides and the lipid bilayer substrate are studied using a molecular level theory of lipid chain packing in membranes. The peptides are modeled as ''amphipathic cylinders'' characterized by a well-defined polar angle. Assuming two-dimensional nematic order of the adsorbed peptides, the membrane perturbation free energy is evaluated using a cell-like model; the peptide axes are parallel to the membrane plane. The elastic and interfacial contributions to the perturbation free energy of the ''peptide-dressed'' membrane are evaluated as a function of: the peptide penetration depth into the bilayer's hydrophobic core, the membrane thickness, the polar angle, and the lipid/peptide ratio. The structural properties calculated include the shape and extent of the distorted (stretched and bent) lipid chains surrounding the adsorbed peptide, and their orientational (C-H) bond order parameter profiles. The changes in bond order parameters attendant upon peptide adsorption are in good agreement with magnetic resonance measurements. Also consistent with experiment, our model predicts that peptide adsorption results in membrane thinning. Our calculations reveal pronounced, membrane-mediated, attractive interactions between the adsorbed peptides, suggesting a possible mechanism for lateral aggregation of membrane-bound peptides. As a special case of interest, we have also investigated completely hydrophobic peptides, for which we find a strong energetic preference for the transmembrane (inserted) orientation over the horizontal (adsorbed) orientation.
The 2008 Annual Meeting, 2008
An increasing number of natural and synthetic peptides with the ability to translocate the plasma membrane are being investigated for their application as drug delivery agents. These cell-penetrating peptides (CPP) are recognized by their capability to enter cells via a nonendocytic and receptor-transporter exclusive pathway [1]. Peptide-membrane interactions and membrane translocation are key properties for intracellular delivery. Although exact mechanisms underlying these interactions remain unknown; they arise ...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2002
Model compounds of modified hydrophobicity (H), hydrophobic moment (W) and angle subtended by charged residues (x) were synthesized to define the general roles of structural motifs of cationic helical peptides for membrane activity and selectivity. The peptide sets were based on a highly hydrophobic, non-selective KLA model peptide with high antimicrobial and hemolytic activity. Variation of the investigated parameters was found to be a suitable method for modifying peptide selectivity towards either neutral or highly negatively charged lipid bilayers. H and W influenced selectivity preferentially via modification of activity on 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) bilayers, while the size of the polar/hydrophobic angle affected the activity against 1-palmitoyl-2-oleoylphosphatidyl-DL-glycerol (POPG). The influence of the parameters on the activity determining step was modest in both lipid systems and the activity profiles were the result of the parameters' influence on the second less pronounced permeabilization step. Thus, the activity towards POPC vesicles was determined by the high permeabilizing efficiency, however, changes in the structural parameters preferentially influenced the relatively moderate affinity. In contrast, intensive peptide accumulation via electrostatic interactions was sufficient for the destabilization of highly negatively charged POPG lipid membranes, but changes in the activity profile, as revealed by the modification of x, seem to be preferentially caused by variation of the low permeabilizing efficiency. The parameters proved very effective also in modifying antimicrobial and hemolytic activity. However, their influence on cell selectivity was limited. A threshold value of hydrophobicity seems to exist which restricted the activity modifying potential of W and x on both lipid bilayers and cell membranes.
The Journal of Physical Chemistry B, 2009
Some membrane-active peptides undergo drastic changes of conformation and/or orientation on water-lipid interfaces. Among the most notable examples is penetratin (pAntp), a short cell-penetrating peptide. To delineate the driving forces behind pAntp-membrane interactions, we used, in this series of two papers, a combined modeling approach that includes: (1) molecular dynamics simulations of pAntp in zwitterionic and anionic lipid bilayers, (2) free energy perturbation calculations of model residue-residue contacts, and (3) detailed analysis of spatial hydrophobic/hydrophilic properties of the peptide/membrane systems. In this first article, we consider the role of conformational plasticity of the peptide in different membrane surroundings, as well as the ability of pAntp to form stable specific residue-residue interactions and make contacts with particular lipids. It was shown that pAntp displays a complicated conformational behavior. Basic and aromatic residues of the peptide form energetically favorable pairs in water and apolar environments, which facilitate membrane insertion of the peptide and stabilization of the membrane-bound state. These residues are also capable of "trapping" lipid heads, thereby affecting their dynamics and microscopic organization of the water-lipid interface. The latter effect is much more pronounced in anionic bilayers and might be related to the initial stage of peptide-induced destabilization of lipid bilayers.
Biochemistry, 2007
The effects of the hydrophobicity and the distribution of hydrophobic residues on the surfaces of some designed α-helical transmembrane peptides (acetyl-K 2 -L m -A n -K 2 -amide, where m + n = 24) on their solution behavior and interactions with phospholipids were examined. We find that although these peptides exhibit strong α-helix forming propensities in water, membrane-mimetic media, and lipid model membranes, the stability of the helices decreases as the Leu content decreases. Also, their binding to reversed phase high-performance liquid chromatography columns is largely determined by their hydrophobicity and generally decreases with decreases in the Leu/ Ala ratio. However, the retention of these peptides by such columns is also affected by the distribution of hydrophobic residues on their helical surfaces, being further enhanced when peptide helical hydrophobic moments are increased by clustering hydrophobic residues on one side of the helix. This clustering of hydrophobic residues also increases peptide propensity for self-aggregation in aqueous media and enhances partitioning of the peptide into lipid bilayer membranes. We also find that the peptides LA 3 LA 2 [acetyl-K 2 -(LAAALAA) 3 LAA-K 2 -amide] and particularly LA 6 [acetyl-K 2 -(LAAAAAA) 3 LAA-K 2 -amide] associate less strongly with and perturb the thermotropic phase behavior of phosphatidylcholine bilayers much less than peptides with higher L/A ratios. These results are consistent with free energies calculated for the partitioning of these peptides between water and phospholipid bilayers, which suggest that LA 3 LA 2 has an equal tendency to partition into water and into the hydrophobic core of phospholipid model membranes, whereas LA 6 should strongly prefer the aqueous phase. We conclude that for α-helical peptides of this type, Leu/Ala ratios of greater than 7/17 are required for stable transmembrane associations with phospholipid bilayers.
The study of the interaction of a model α-helical peptide with lipid bilayers and monolayers
Bioelectrochemistry, 2004
We studied the interaction of the a-helical peptide acetyl -Lys 2 -Leu 24 -Lys 2 -amide (L 24 ) with tethered bilayer lipid membranes (tBLM) and lipid monolayers formed at an air -water interface. The interaction of L 24 with tBLM resulted in adsorption of the peptide to the surface of the bilayer, characterized by a binding constant K c = 2.4 F 0.6 AM À 1 . The peptide L 24 an induced decrease of the elasticity modulus of the tBLM in a direction perpendicular to the membrane surface, E ? . The decrease of E ? with increasing peptide concentration can be connected with a disordering effect of the peptide to the tBLM structure. The pure peptide formed a stable monolayer at the air/water interface. The pressure -area isotherms were characterized by a transition of the peptide monolayer, which probably corresponds of the partial intercalation of the a-helixes at higher surface pressure. Interaction of the peptide molecules with lipid monolayers resulted in an increase of the mean molecular area of phospholipids both in the gel and liquid crystalline states. With increasing peptide concentration, the temperature of the phase transition of the monolayer shifted toward lower temperatures. The analysis showed that the peptide -lipid monolayer is not an ideally miscible system and that the peptide molecules form aggregates in the monolayer. D
The engineering of membrane-permeable peptides
Analytical Biochemistry, 2005
Reversible lipid attachment was investigated as a means to deliver small peptides into cells. Two labile straight chain alkyl motifs were developed: a cysteine dodecane disulWde (Cdd) building block and a tyrosine-or serine-myristate ester. Both moieties are cleaved on cell internalization and are compatible with Fmoc solid phase peptide synthesis. A series of Xuorophore-labeled peptides that varied in lipophilic content, net charge, and charge distribution were synthesized. The peptides were screened for cellular uptake eYciency as monitored by Xuorescence microscopy. EVective peptide transport is based on a distributed net positive charge introduced as lysine residues at the C and/or N terminus of the peptide and the presence of a hydrophobic domain exhibiting an estimated log P 7 4.0. The incorporation of labile lipid motifs into peptides enhances lipophilic character of the peptides and contributes to cellular uptake with minimal alteration to the native sequence.