Effect of Peptide Lipidation on Membrane Perturbing Activity:  A Comparative Study on Two Trichogin Analogues

Abstract

The effect of lipidation on the membrane perturbing activity of peptaibol antibiotics was investigated by performing a comparative study on two synthetic analogues of the natural peptide trichogin GA IV. Both analogues were labeled with a hydrophobic fluorescent probe, but one of them lacked the N-terminal n-octanoyl chain, present in the natural peptide. Spectroscopic studies show that the fatty acyl chain produces two opposite effects: it increases the affinity of the monomeric peptide for the membrane phase, but, at the same time, it favors peptide aggregation in water, thus inhibiting membrane binding by reducing the effective monomer concentration. In the membrane phase the two analogues exhibit the same aggregation and orientation behavior, indicating that the n-octanoyl chain plays no specific role in determining their orientation or membrane perturbing activity. Indeed, the dependence of peptide-induced membrane leakage on total peptide concentration is basically the same for the two analogues, because the aforementioned opposite effects, caused by peptide lipidation, tend to balance. These findings make questionable the use of lipidation as a general method for increasing the peptide membrane-perturbing activity, as its validity seems to be restricted to parent compounds of limited overall hydrophobicity.

Metal Binding Properties of Fluorescent Analogues of Trichogin GA IV: A Conformational Study by Time‐Resolved Spectroscopy and Molecular Mechanics Investigations

“…The procedure for liposome preparation has already been reported. [35] MM calculations were carried out by using a homemade program linked to Hyperchem 7.0, [36] with a MM + force field implemented with the TOAC parameters. [37] …”

Converting Peptides into Drug Leads by Lipidation

“…Despite of the less hydrophobicity of propanoyl group compare to octanoyl group, N-propanoylmastoparan-X showed reduced free energy upon insertion of water into the membrane compared to N-octanoylation-mastoparan-X [98]. Lipidation may have negative effects on the membrane binding properties of lipidated peptides due to the increased aggregation propensity and the reduced effective monomer concentration [112].…”

Fluorescence spectroscopy and molecular dynamics simulations in studies on the mechanism of membrane destabilization by antimicrobial peptides

“…Aggregation in water screens the hydrophobic portions of the peptide sequence and competes with association to the membrane [64,121]. Aggregation in the membrane may be part of the pore formation process, as in the case of peptides acting according to the barrel-stave model [28,122].…”

“…Usually, formation of aggregates will change the environment around the fluorophore, and thus become detectable by changes in intensity, fluorescence lifetime, or spectral position with peptide concentration [64,121,123]. Quantitative analysis of fluorescence lifetimes is complicated for intrinsic fluorescence by the nonexponential decay of the Trp fluorophore, even under monomeric conditions.…”

“…However, in those cases in which the monomeric peptide exhibits a monoexponential decay (as in peptides labeled with fluorene), the pre-exponential factors of the different lifetimes observed in the presence of aggregation provide the relative populations of the different species. For instance, for the trichogin GA IV analogues F10 and F0, with a global analysis of the fluorescence decays, we were able to measure the population of the four different species formed by these peptides (monomers and aggregates, both in water and in the membrane) [64,121,123] (Fig. 3).…”