Lipopeptaibols are members of a novel group of naturally occurring, short peptides with antimicrobial activity, characterized by a lipophilic acyl chain at the N-terminus, a high content of the ...turn/helix forming alpha-aminoisobutyric acid and a 1,2-amino alcohol at the C-terminus. The amino acid sequences range from 6 to 10 residues and the fatty acyl moieties from 8 to 15 carbon atoms. The peptide portion of lipopeptaibols can be shorter than those of the nonlipidated peptaibols that range from 10 to 19 amino acid residues. The longest peptides fold into a mixed 3(10)/alpha helix, whereas the shortest peptides tend to adopt a beta-turn/sheet structure. Using solution methodologies, a series of analogues of trichogin GA IV was synthesized which allowed determination of the minimal lipid chain and peptide main-chain lengths for the onset of membrane activity and exploitation of a number of spectroscopic techniques aimed at determining its preferred conformation under a variety of conditions and investigating in detail its mode of interaction with, and its effect on, the phospholipid membranes.
The development of protective and safe textiles is of fundamental importance for defending the human body from bacterial infections. To this aim, garments are often functionalized with antibacterial ...agents. We recently started a program aimed at covalently linking antimicrobial peptides to cotton tissues. To optimize the process of binding, it is necessary to know the degree of functionalization and how deeply peptides penetrate into the cotton fiber. Here, we present a spin-label electron paramagnetic resonance (EPR) approach for obtaining data on the peptide incorporation into the fibers. The approach is based on the line broadening in conventional EPR and on the signal decays in electron spin echo spectroscopy that is a pulsed version of EPR.
The lipopeptaibol trichogin GA IV is a 10 amino acid-long residue and
α-aminoisobutyric acid-rich antibiotic peptide of fungal origin. TOAC (2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic ...acid) spin-labeled analogs of this membrane active peptide were investigated in hydrated bilayers of dipalmitoylphosphatidylcholine by electron spin echo envelope modulation (ESEEM) spectroscopy and pulsed electron-electron double resonance (PELDOR). Since, the ESEEM of the spin label appears to be strongly dependent on the presence of water molecules penetrated into the membrane, this phenomenon was used to study the location of this peptide in the membrane. This was achieved by comparing the ESEEM spectra for peptides labeled at different positions along the amino acid sequence with spectra known for lipids with spin labels at different positions along the hydrocarbon chain. To increase the ESEEM amplitude and to distinguish the hydrogen nuclei of water from lipid protons, membranes were hydrated with deuterated water. The PELDOR spectroscopy technique was chosen to study peptide aggregation and to determine the mutual distance distribution of the spin-labeled peptides in the membrane. The location of the peptide in the membrane and its aggregation state were found to be dependent on the peptide concentration. At a low peptide/lipid molar ratio (less than 1:100) the nonaggregated peptide chain of the trichogin molecules lie parallel to the membrane surface, with TOAC at the 4th residue located near the 9th–11th carbon positions of the
sn-2 lipid chain. Increasing this ratio up to 1:20 leads to a change in peptide orientation, with the N-terminus of the peptide buried deeper into membrane. Under these conditions peptide aggregates are formed with a mean aggregate number of about
N
=
2. The aggregates are further characterized by a broad range of intermolecular distances (1.5–4
nm) between the labels at the N-terminal residues. The major population exhibits a distance of ∼2.5
nm, which is of the same order as the length of the helical peptide. We suggest that the constituting monomers of the dimer are antiparallel oriented.
p53-related protein kinase (PRPK), the human homologue of yeast Bud32, belonging to a small subfamily of atypical protein kinases, is inactive unless it is previously incubated with cell lysates. ...Here we show that such an activation of PRPK is mediated by another kinase, Akt/PKB, which phosphorylates PRPK at Ser250. We show that recombinant PRPK is phosphorylated in vitro by Akt and its phospho-form is recognized by a Ser250-phospho-specific antibody; that cell co-transfection with Akt along with wild-type PRPK, but not with its Ser250Ala mutant, results in increased PRPK phosphorylation; and that the phosphorylation of p53 at Ser15, the only known substrate of PRPK, is markedly increased by co-transfection of Akt with wild-type PRPK, but not PRPK dead mutant, and is abrogated by cell treatment with the Akt pathway inhibitor LY294002. Our data disclose an unanticipated mechanism by which PRPK can be activated and provide a functional link between this enigmatic kinase and the Akt signaling pathway.
Trichogin: a paradigm for lipopeptaibols Peggion, Cristina; Formaggio, Fernando; Crisma, Marco ...
Journal of peptide science,
November ‐ December 2003, Letnik:
9, Številka:
11-12
Journal Article
Trichogin GA IV, an 11-residue lipopeptaibol blocked at the N-terminus by an n-octanoyl group and at the C-terminus by a 1,2-amino alcohol (l-leucinol), extracted from the fungus Trichoderma ...longibrachiatum, exhibits remarkable membrane-modifying properties. We have synthesized trichogin GA IV and several l-Leu-OMe11 analogs carrying at the N-terminus an acyl chain of variable length (C2−C8, C10, C12, C14, C16, C18). A succinoylated head-to-head dimer was also prepared. A conformational analysis, carried out by FTIR absorption, CD, and NMR, showed that the right-handed helical structure of the natural lipopeptaibol is essentially preserved in all its analogs. Permeability measurements revealed that at least six carbon atoms in the Nα-blocking fatty acyl moiety are required for the onset of significant membrane-modifying properties. Also the head-to-head dimer is remarkably active. Possible models for the mechanism of membrane permeability of trichogin GA IV are discussed.
The terminally protected, linear, homo-β-peptides Boc-(R)-β2,2-HBinn-OMe (n=2–6) as well as the cyclic homo-β-peptides c(R)-β2,2-HBin3 and c(S)-β2,2-HBin4, all derived from the ...2′,1′:1,2;1″,2″:3,4-dinaphthcyclohepta-1,3-diene-6-aminomethyl-6-carboxylic acid residue β2,2-HBin possessing only axial chirality, have been synthesized in solution by the EDC/AtOH coupling method for chain elongation, and by cyclization of pentafluorophenyl esters. A conformational analysis suggested the concomitant occurrence of different intramolecularly H-bonded forms for the linear oligomers in solution.
PDF
