Amphiphilic Α-helical Peptides Research Articles

Effects of mastoparan B and its analogs on the phospholipase D activity in L1210 cells

Mastoparan B (MP-B), an amphiphilic α-helical peptide isolated from hornet venom, and its Ala-substituted analogs were examined for their effectiveness on phospholipase D (PLD) activity in L1210 cells. PLD activity was determined by measuring phosphatidylethanol produced from [ 3H]myristate-labelled cells in the presence of ethanol. PLD activity was stimulated by MP-B, 4MP-B (Lys 4→Ala), and 12MP-B (Lys 12→Ala), but not by 3MP-B (Leu 3→Ala) and 9MP-B (Trp 9→Ala). Other MPs including mastoparan 7 also stimulated the PLD activity, but inactive mastoparan 17 did not. The stimulatory effect of various MP analogs could be correlated with their α-helical contents. The PLD activity stimulated by MP-B was not affected by G-protein blocking chemicals. The extent of PLD stimulation by various MP-Bs, as well as by digitonin and β-escin, correlated with the permeability of the membrane to ethidium bromide. These results suggest that the stimulation of PLD activity by MP-B in L1210 cells is probably coupled with membrane perturbation brought about by the peptide.

N- and C-Terminal Effect of Amphiphilic α-Helical Peptides on the Interaction with Model- and Bio-Membranes

Abstract We previously designed and synthesized five N- and C-termini-free amphiphilic α-helical model peptides (Hel series) with a systematically varied hydrophobic–hydrophilic balance (HHB) that showed hemolytic activity, but no antimicrobial activity. However, an N-acetylated and C-amidated model peptide, peptide 3 [S. E. Blondelle and R. A. Houghten, Biochemistry, 31, 12688 (1992)], similar to a Hel series peptide, Hel 9-9, whose hydrophobic and hydrophilic amino acid residues and areas are equal in the α-helical structure, have exhibited both hemolytic and antimicrobial activities. Thus, to investigate the N- and C-terminal effect of the Hel series peptides on their antimicrobial activity, we designed and synthesized three peptides (Cap-Hel series), both termini-blocked by N-acetyl and C-amide groups. Their interaction mode with membranes was examined through reverse-phase high-performance liquid chromatography and circular dichroism spectroscopy as well as measurements of the hemolytic activity, antimicrobial activity, and membrane-clearing ability. No essential difference was found in either the terminal-free or -protected peptides, indicating that acetylation of the N-terminal and amidation of C-terminal did not affect their intrinsic antimicrobial activity in spite of a considerable change in the binding properties to lipids and hemolytic activities.

Stimuli-responsive formation of helical polypeptide rod assemblies

Two association states of helical polypeptide rods that mimic protein structures, the head-to-head association and side-b γ-side association, were studied. Helix-helix association of α-helical polypeptides was induced by external stimuli of alkaline metal ions. An α-helical polypeptide having a terminal benzo-15-crown-5 was synthesized. Head-to-head type interconnection of the polypeptides was regulated by sodium or potassium ions. Assembly structures of helical polypeptide rods and their functions were controlled by external photostimuli. A photoresponsive amphiphilic sequential polypeptide composed of two amphiphilic α-helical copoly peptides, poly [( γ-methyl- l-glutamate) -co- ( l-glutamic acid)], joined by an azobenzene, was synthesized. In an aqueous solution, the polypeptides formed a micelle with a side-b γ-side association, and the photoinduced structural changes of the polypeptide resulted in disaggregation of the micelle. In a lipid bilayer membrane, the polypeptides formed a transmembrane bundle with a side-by-side association, and the photoinduced structural changes of the polypeptide resulted in destabilization of the bundle. Photoinduced reversible structural changes of the polypeptide in the bilayer membrane could regulate transmembrane ion transport.

A Hybrid of Amphiphilic α-Helical Peptides and meso-Tetra(α,α,α,α-o-carboxyphenyl)porphyrin. Membrane-Penetrating Porphyrin-4α-Helix Artificial Protein

Abstract Four amphiphilic α-helical peptides were hybridized with α,α,α,α-isomer of meso-tetra(o-carboxyphenyl)porphyrin to synthesize a picket-fence-type 4α-helix bundle polypeptide. The peptide sequence was designed so that the hybrid polypeptide could penetrate into phospholipid bilayers. Circular dichroism spectra showed that the hybrid folds in a complete four α-helix bundle structure both in methanol and dipalmitoylphosphatidylcholine vesicles.

Multicyclic polypeptide model compounds. 1. Synthesis of a tricyclic amphiphilic .alpha.-helical peptide using an oxime resin, segment-condensation approach

An idealized model amphiphilic α-helical peptide, cyclo(3-7,10-14,17-21)H-[LysLeuLysGluLeuLysGlu] 3 -OH (peptide 1-1-1), comprising three repeats of a Lys 3 -Glu 7 side-chain bridged heptapeptide, has been synthesized by a generally applicable segment-condensation approach that involves a novel solid-phase cyclization reaction. The linear heptapeptide, Boc-Lys-(2Cl-Z)LeuLys(Trt)Glu(OBzl)LeuLys(2Cl-Z)Glu(oxime resin)-OPac, was built on a p-nitrobenzophenone oxime derivatized polystyrene solid support by standard methods. Circular dichroism spectra indicated that peptide 1-1-1 adopted mostly disordered conformations in aqueous solution, but a high α-helix content was induced in 50% TFE and upon adsorption of peptide 1-1-1 from aqueous solution onto siliconized quartz slides

Photolabeling of Calmodulin with Basic, Amphiphilic α-Helical Peptides Containing p-Benzoylphenylalanine

A novel photoreactive amino acid has been incorporated synthetically into two model peptides and the calmodulin-binding domain from myosin light chain kinase. Cross-linked photoadducts of each peptide with calmodulin have been prepared and digested by chemical and/or enzymatic methods to determine the site of label attachment. Depending on the position of the photoprobe in the peptide sequence, either Met-144 or Met-71 is photolabeled. These results are discussed in relation to the three-dimensional structure of calmodulin obtained crystallographically and the known solution properties of calmodulin.