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What Goes around Comes around-A Comparative Study of the Influence of Chemical Modifications on the Antimicrobial Properties of Small Cyclic Peptides.

Scheinpflug K, Nikolenko H, Komarov IV, Rautenbach M, Dathe M - Pharmaceuticals (Basel) (2013)

Bottom Line: Our current studies focus on elucidating a putative membrane translocation mechanism whereupon the peptides might interfere with intracellular processes.We found that minimal changes in both the cationic and hydrophobic domain of the peptides in most cases led to significant reduction of antimicrobial activity and/or changes in the mode of action.However, we were able to identify two modified peptides which exhibited properties similar to those of the cyclic parent hexapeptide and are suitable for subsequent studies on membrane translocation and uptake into bacterial cells.

View Article: PubMed Central - PubMed

Affiliation: Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Str. 10, Berlin 13125, Germany. dathe@fmp-berlin.de.

ABSTRACT
Tryptophan and arginine-rich cyclic hexapeptides of the type cyclo-RRRWFW combine high antibacterial activity with rapid cell killing kinetics, but show low toxicity in human cell lines. The peptides fulfil the structural requirements for membrane interaction such as high amphipathicity and cationic charge, but membrane permeabilisation, which is the most common mode of action of antimicrobial peptides (AMPs), could not be observed. Our current studies focus on elucidating a putative membrane translocation mechanism whereupon the peptides might interfere with intracellular processes. These investigations require particular analytical tools: fluorescent analogues and peptides bearing appropriate reactive groups were synthesized and characterized in order to be used in confocal laser scanning microscopy and HPLC analysis. We found that minimal changes in both the cationic and hydrophobic domain of the peptides in most cases led to significant reduction of antimicrobial activity and/or changes in the mode of action. However, we were able to identify two modified peptides which exhibited properties similar to those of the cyclic parent hexapeptide and are suitable for subsequent studies on membrane translocation and uptake into bacterial cells.

No MeSH data available.


Related in: MedlinePlus

Bacterial membrane permeabilisation determined with flow cytometry using propidium iodide (PI). PI influx after incubation with cWFW, fluorescent-labeled and K-substituted cyclic hexapeptides was tested into B. subtilis DSM 347 (A,C) and E. coli DH5α (B,D) at respective MICs. The antibiotic polymyxin B (5 µM) and the helical model peptide KLA-1 (KLALKLALKALKAALKLA-NH2, 5 µM) obtain a high membrane permeabilising potential and served as positive control in Gram-negative and Gram-positive cells, respectively (solid line) [20,34]. Preparations without peptide were used as negative control (dotted line).
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pharmaceuticals-06-01130-f004: Bacterial membrane permeabilisation determined with flow cytometry using propidium iodide (PI). PI influx after incubation with cWFW, fluorescent-labeled and K-substituted cyclic hexapeptides was tested into B. subtilis DSM 347 (A,C) and E. coli DH5α (B,D) at respective MICs. The antibiotic polymyxin B (5 µM) and the helical model peptide KLA-1 (KLALKLALKALKAALKLA-NH2, 5 µM) obtain a high membrane permeabilising potential and served as positive control in Gram-negative and Gram-positive cells, respectively (solid line) [20,34]. Preparations without peptide were used as negative control (dotted line).

Mentions: In order for the fluorescence-labeled and K-containing derivatives to be applicable in investigations on the mode of action of our cyclic hexapeptides, the chemical modifications must have no or only little influence on the properties of cWFW. As all peptide analogues used in this study fulfil the structural prerequisites for membrane interaction, i.e., high amphipathicity and positive net charge, we investigated their potential to permeabilise the bacterial membrane (Figure 4).


What Goes around Comes around-A Comparative Study of the Influence of Chemical Modifications on the Antimicrobial Properties of Small Cyclic Peptides.

Scheinpflug K, Nikolenko H, Komarov IV, Rautenbach M, Dathe M - Pharmaceuticals (Basel) (2013)

Bacterial membrane permeabilisation determined with flow cytometry using propidium iodide (PI). PI influx after incubation with cWFW, fluorescent-labeled and K-substituted cyclic hexapeptides was tested into B. subtilis DSM 347 (A,C) and E. coli DH5α (B,D) at respective MICs. The antibiotic polymyxin B (5 µM) and the helical model peptide KLA-1 (KLALKLALKALKAALKLA-NH2, 5 µM) obtain a high membrane permeabilising potential and served as positive control in Gram-negative and Gram-positive cells, respectively (solid line) [20,34]. Preparations without peptide were used as negative control (dotted line).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3818835&req=5

pharmaceuticals-06-01130-f004: Bacterial membrane permeabilisation determined with flow cytometry using propidium iodide (PI). PI influx after incubation with cWFW, fluorescent-labeled and K-substituted cyclic hexapeptides was tested into B. subtilis DSM 347 (A,C) and E. coli DH5α (B,D) at respective MICs. The antibiotic polymyxin B (5 µM) and the helical model peptide KLA-1 (KLALKLALKALKAALKLA-NH2, 5 µM) obtain a high membrane permeabilising potential and served as positive control in Gram-negative and Gram-positive cells, respectively (solid line) [20,34]. Preparations without peptide were used as negative control (dotted line).
Mentions: In order for the fluorescence-labeled and K-containing derivatives to be applicable in investigations on the mode of action of our cyclic hexapeptides, the chemical modifications must have no or only little influence on the properties of cWFW. As all peptide analogues used in this study fulfil the structural prerequisites for membrane interaction, i.e., high amphipathicity and positive net charge, we investigated their potential to permeabilise the bacterial membrane (Figure 4).

Bottom Line: Our current studies focus on elucidating a putative membrane translocation mechanism whereupon the peptides might interfere with intracellular processes.We found that minimal changes in both the cationic and hydrophobic domain of the peptides in most cases led to significant reduction of antimicrobial activity and/or changes in the mode of action.However, we were able to identify two modified peptides which exhibited properties similar to those of the cyclic parent hexapeptide and are suitable for subsequent studies on membrane translocation and uptake into bacterial cells.

View Article: PubMed Central - PubMed

Affiliation: Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Str. 10, Berlin 13125, Germany. dathe@fmp-berlin.de.

ABSTRACT
Tryptophan and arginine-rich cyclic hexapeptides of the type cyclo-RRRWFW combine high antibacterial activity with rapid cell killing kinetics, but show low toxicity in human cell lines. The peptides fulfil the structural requirements for membrane interaction such as high amphipathicity and cationic charge, but membrane permeabilisation, which is the most common mode of action of antimicrobial peptides (AMPs), could not be observed. Our current studies focus on elucidating a putative membrane translocation mechanism whereupon the peptides might interfere with intracellular processes. These investigations require particular analytical tools: fluorescent analogues and peptides bearing appropriate reactive groups were synthesized and characterized in order to be used in confocal laser scanning microscopy and HPLC analysis. We found that minimal changes in both the cationic and hydrophobic domain of the peptides in most cases led to significant reduction of antimicrobial activity and/or changes in the mode of action. However, we were able to identify two modified peptides which exhibited properties similar to those of the cyclic parent hexapeptide and are suitable for subsequent studies on membrane translocation and uptake into bacterial cells.

No MeSH data available.


Related in: MedlinePlus