Membrane association and activity of 15/16-membered peptide antibiotics: Zervamicin IIB, ampullosporin A and antiamoebin I

Abstract

Permeabilization of the phospholipid membrane, induced by the antibiotic peptides zervamicin IIB (ZER), ampullosporin A (AMP) and antiamoebin I (ANT) was investigated in a vesicular model system. Membrane-perturbing properties of these 15/16 residue peptides were examined by measuring the K(+) transport across phosphatidyl choline (PC) membrane and by dissipation of the transmembrane potential. The membrane activities are found to decrease in the order ZER>AMP>>ANT, which correlates with the sequence of their binding affinities. To follow the insertion of the N-terminal Trp residue of ZER and AMP, the environmental sensitivity of its fluorescence was explored as well as the fluorescence quenching by water-soluble (iodide) and membrane-bound (5- and 16-doxyl stearic acids) quenchers. In contrast to AMP, the binding affinity of ZER as well as the depth of its Trp penetration is strongly influenced by the thickness of the membrane (diC(16:1)PC, diC(18:1)PC, C(16:0)/C(18:1)PC, diC(20:1)PC). In thin membranes, ZER shows a higher tendency to transmembrane alignment. In thick membranes, the in-plane surface association of these peptaibols results in a deeper insertion of the Trp residue of AMP which is in agreement with model calculations on the localization of both peptide molecules at the hydrophilic-hydrophobic interface. The observed differences between the membrane affinities/activities of the studied peptaibols are discussed in relation to their hydrophobic and amphipathic properties.

The role of hydrophobic interactions in positioning of peripheral proteins in membranes

“…The energetic differences between the transmembrane and surface orientations of all peptaibols (alamethicin, zervamicin, and antiamoebin, Table 2) were found to be < 3 kcal/mol. The transmembrane orientation was energetically preferred for alamethicin and chrysospermin C, whereas the tilted orientation was more favorable for all other peptaibols, in agreement with fluorescence and NMR studies of the peptaibols [44-47]. …”

Antiamoebin I in Methanol Solution: Rapid Exchange between Right‐Handed and Left‐Handed 310‐Helical Conformations

“…This is indeed the case. As reported [18], in spite of the larger hydrophobicity of Aam-I, it has a significantly lower binding affinity to lipid vesicles than Zrv-IIB.…”

Exploring the Membrane Mechanism of the Bioactive Peptaibol Ampullosporin A Using Lipid Monolayers and Supported Biomimetic Membranes

“…In eggPC vesicles, a small fraction of bound AmpA is also involved in the formation of a transmembrane state [32]. Thus, the supported membrane disorganization triggered by the peptaibol unlikely results from a TM orientation of AmpA monomers in the membrane and is thus inconsistent with the formation of well-defined pores.…”

“…As for Alm, a correlation between AmpA bioactivities and its ability to permeabilize membranes has been suggested [30, 31]. AmpA interacts with egg yolk L - α -phosphatidylcholine (eggPC) vesicles in the absence of membrane voltage [32]. Its length (23 Å in the crystals) [33] has to be compared to the hydrophobic core of natural membranes typically having a thickness ranging from 30 to 40 Å [34].…”

“…Although the studies previously undertaken on various artificial lipid platforms and using various analytical techniques [32, 36] brought invaluable information on the mode of interaction of AmpA with membranes, the coupling of analytical techniques such as FRAP and SPR on complementary membrane models and under comparable experimental conditions (i.e., type and concentration of buffer system) can prove very useful to examine the various steps of the peptaibol membrane mechanism. Among the available membrane models, supported lipid membranes [37, 38] allow studying peptide interaction at the lipid/water interface.…”