Structure-Activity Relationships of Diastereomeric Lysine Ring Size Analogs of the Antimicrobial Peptide Gramicidin S

Abstract

Structure-activity relationships were examined in seven gramicidin S analogs in which the ring-expanded analog GS14 [cyclo-(VKLKVdYPLKVKLdYP)] is modified by enantiomeric inversions of its lysine residues. The conformation, amphiphilicity, and self-association propensity of these peptides were investigated by circular dichroism spectroscopy and reversed phase high performance liquid chromatography. 31 P nuclear magnetic resonance spectroscopic and dye leakage experiments were performed to evaluate the capacity of these peptides to induce inverse nonlamellar phases in, and to permeabilize phospholipid bilayers; their growth inhibitory activity against the cell wall-less mollicute Acholeplasma laidlawii B was also examined. The amount and stability of ␤-sheet structure, effective hydrophobicity, propensity for self-association in water, ability to disrupt the organization of phospholipid bilayers, and ability to inhibit A. laidlawii B growth are strongly correlated with the facial amphiphilicity of these GS14 analogs. Also, the magnitude of the parameters segregate these peptides into three groups, consisting of GS14, the four single inversion analogs, and the two multiple inversion analogs. The capacity of these peptides to differentiate between bacterial and animal cell membranes exhibits a biphasic relationship with peptide amphiphilicity, suggesting that there may only be a narrow range of peptide amphiphilicity within which it is possible to achieve the dual therapeutic requirements of high antibiotic effectiveness and low hemolytic activity. These results were rationalized by considering how the physiochemical properties of these GS14 analogs are likely to be reflected in their partitioning into lipid bilayer membranes.

Gramicidin S identified as a potent inhibitor for cytochrome bd‐type quinol oxidase

“…4) although it is generally assumed that the principal target of GS is the membrane lipid bilayer rather than the protein components. Recent studies have shown that structural analogs of GS can be designed with markedly reduced hemolytic activity and enhanced microbial activity, suggesting the possibility of GS derivatives as potent oral or injectable broad-spectrum antibiotics [9,[20][21][22]. Our finding would provide a new insight into the molecular design and development of novel GS-based antibiotics (see Fig.…”

“…From the screening of hundreds of natural antibiotics in the Kitasato Institute for Life Sciences Chemical Library [19], we found the inhibitory activity of GS for Escherichia coli cytochrome bd. Recent studies have shown that GS analogs can be designed with the markedly improved therapeutic index, suggesting the possibility of GS derivatives as potent broad-spectrum antibiotics [9,[20][21][22]. Our finding would provide a new insight into molecular design and development of new GS analogs.…”

Biomimetic Model Membrane Systems Serve as Increasingly Valuable in Vitro Tools

“…It was determined that lipid flip-flop, membrane leakiness, and peptide translocation could not individually be related to AMP structure or charge, concluding that many factors must be involved in AMP activity which have a varying impact on membranes (Zhang et al, 2001). In a detailed investigation, it was shown that the ability of gramicidin S to differentiate between mammalian and bacterial membranes depended on many peptide parameters as well, such as solubility, beta-sheet content, self-aggregation propensity, hydrophobicity and amphiphilicity (Prenner et al, 2005). These examples illustrate how changing the properties of the model system can illuminate the interactions involved.…”

Trans-Bilayer Ion Conduction by Proline Containing Cyclic Hexapeptides and Effects of Amino Acid Substitutions on Ion Conducting Properties

“…9,10 However, there is still no consensus about the principles governing the formation of pores that can assist their design. Additionally, correlation of peptide conformations with ion channel function also needs to be clarified for appropriate engineering of pore constructions.…”

“…9,10 Therefore, effects of cationic and hydrophobic characteristics of cyclic peptides on ion conducting properties should be addressed. On the basis of these points, hydrophobic Leu or cationic/hydrophilic Lys were incorporated into Pro containing cyclic hexapeptide constructs and ion conducting properties were compared.…”