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Amphipathic Peptides (amphipathic + peptide)
Selected AbstractsEvidence for an amphipathicity independent cellular uptake of amphipathic cell-penetrating peptidesFEBS JOURNAL, Issue 19 2000Anne Scheller The cellular uptake of a peptide set derived from membrane-permeable ,-helical amphipathic peptides by stepwise alterations of structure forming propensity and charge was studied by confocal laser scanning microscopy (CLSM) combined with HPLC. For CLSM monitoring, an online protocol was employed that avoided bias of the uptake results by washout. Using this protocol, extensive fluorescence, approaching the intensity of the external peptide, was observed in the cytosol and nucleus within minutes in all cases, irrespective of the degree of amphipathicity. HPLC analyses of the cell lysates revealed the unmetabolized peptides to be the predominant source of the intracellular fluorescence. Significant amphipathicity-dependent differences became apparent only after washing the peptide-loaded cells, reflecting the effects of amphipathicity on resistance to wash out. Exposure of the cells to the peptides at 37 and 0 °C led to similar results, indicating the nonendocytic character of the uptake. With a view to practical applications , the results of the present study open the possibility of exploiting nonamphipathic peptides as vectors for translocating polar compounds into the cell interior, which would circumvent substantial obstacles currently connected with the use of amphipathic vector peptides, such as membrane toxicity and low solubility. Moreover, differences in the uptake of several members of the investigated peptide series into different cell types present a promising basis for the design of cell-type specific vector peptides. [source] Studies on the cellular uptake of substance P and lysine-rich, KLA-derived model peptides,JOURNAL OF MOLECULAR RECOGNITION, Issue 1 2005Johannes Oehlke Abstract In the last decade many peptides have been shown to be internalized into various cell types by different, poorly characterized mechanisms. This review focuses on uptake studies with substance P (SP) aimed at unravelling the mechanism of peptide-induced mast cell degranulation, and on the characterization of the cellular uptake of designed KLA-derived model peptides. Studies on structure,activity relationships and receptor autoradiography failed to detect specific peptide receptors for the undecapeptide SP on mast cells. In view of these findings, a direct interaction of cationic peptides with heterotrimeric G proteins without the participation of a receptor has been proposed. Such a process would require insertion into and translocation of peptides across the plasma membrane. In order to clarify whether a transport of cationic peptides into rat peritoneal mast cells is possible, transport studies were performed by confocal laser scanning microscopy (CLSM) using fluorescence-labeled Arg3,Orn7 -SP and its D -amino acid analog, all- D -Arg3,Orn7 -SP, as well as by electron microscopic autoradiography using 3H-labelled SP and 125I-labelled all- D -SP. The results obtained by CLSM directly showed translocation of SP peptides into pertussis toxin-treated cells. Kinetic experiments indicated that the translocation process was rapid, occurring within a few seconds. Mast cell degranulation induced by analog of magainin 2 amide, neuropeptide Y and the model peptide acetyl-KLALKLALKALKAALKLA-amide was also found to be very fast, pointing to an extensive translocation of the peptides. In order to learn more about structural requirements for the cellular uptake of peptides, the translocation behavior of a set of systematically modified KLA-based model peptides has been studied in detail. By two different protocols for determining the amount of internalized peptide, evidence was found that the structure of the peptides only marginally affects their uptake, whereas the efflux of cationic, amphipathic peptides is strikingly diminished, thus allowing their enrichment within the cells. Although the mechanism of cellular uptake, consisting of energy-dependent and -independent contributions, is not well understood, KLA-derived peptides have been shown to deliver various cargos (PNAs, peptides) into cells. The results obtained with SP- and KLA-derived peptides are discussed in the context of the current literature. Copyright © 2004 John Wiley & Sons, Ltd. [source] A novel method reveals that solvent water favors polyproline II over ,-strand conformation in peptides and unfolded proteins: conditional hydrophobic accessible surface area (CHASA)PROTEIN SCIENCE, Issue 1 2005Patrick J. Fleming Abstract In aqueous solution, the ensemble of conformations sampled by peptides and unfolded proteins is largely determined by their interaction with water. It has been a long-standing goal to capture these solute-water energetics accurately and efficiently in calculations. Historically, accessible surface area (ASA) has been used to estimate these energies, but this method breaks down when applied to amphipathic peptides and proteins. Here we introduce a novel method in which hydrophobic ASA is determined after first positioning water oxygens in hydrogen-bonded orientations proximate to all accessible peptide/protein backbone N and O atoms. This conditional hydrophobic accessible surface area is termed CHASA. The CHASA method was validated by predicting the polyproline-II (PII) and ,-strand conformational preferences of non-proline residues in the coil library (i.e., non-,-helix, non-,-strand, non-,-turn library derived from X-ray elucidated structures). Further, the method successfully rationalizes the previously unexplained solvation energies in polyalanyl peptides and compares favorably with published experimentally determined PII residue propensities. We dedicate this paper to Frederic M. Richards. [source] Amphipathic control of the 310 -/,-helix equilibrium in synthetic peptidesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2001L. G. J. Hammarström Abstract: A series of short, amphipathic peptides incorporating 80% C,,C, -disubstituted glycines has been prepared to investigate amphipathicity as a helix-stabilizing effect. The peptides were designed to adopt 310 - or ,-helices based on amphipathic design of the primary sequence. Characterization by circular dichroism spectroscopy in various media (1,:,1 acetonitrile/water; 9,:,1 acetonitrile/water; 9,:,1 acetonitrile/TFE; 25 mm SDS micelles in water) indicates that the peptides selectively adopt their designed conformation in micellar environments. We speculate that steric effects from ith and ith + 3 residues interactions may destabilize the 310 -helix in peptides containing amino acids with large side-chains, as with 1-aminocyclohexane-1-carboxylic acid (Ac6c). This problem may be overcome by alternating large and small amino acids in the ith and ith + 3 residues, which are staggered in the 310 -helix. [source] | ||||||||||