Int. J. Mol. Sci. 2013, 14(1), 2190-2202; doi:10.3390/ijms14012190

Effect of Repetitive Lysine-Tryptophan Motifs on the Eukaryotic Membrane

1email, 1email, 2email, 2email, 3email, 3email and 1,2,* email
Received: 27 November 2012; in revised form: 14 January 2013 / Accepted: 15 January 2013 / Published: 22 January 2013
(This article belongs to the Special Issue Phospholipids: Molecular Sciences 2012)
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Abstract: In a previous study, we synthesized a series of peptides containing simple sequence repeats, (KW)nNH2 (n = 2,3,4 and 5) and determined their antimicrobial and hemolytic activities, as well as their mechanism of antimicrobial action. However, (KW)5 showed undesirable cytotoxicity against RBC cells. In order to identify the mechanisms behind the hemolytic and cytotoxic activities of (KW)5, we measured the ability of these peptides to induce aggregation of liposomes. In addition, their binding and permeation activities were assessed by Trp fluorescence, calcein leakage and circular dichrorism using artificial phospholipids that mimic eukaryotic liposomes, including phosphatidylcholine (PC), PC/sphingomyelin (SM) (2:1, w/w) and PC/cholesterol (CH) (2:1, w/w). Experiments confirmed that only (KW)5 induced aggregation of all liposomes; it formed much larger aggregates with PC:CH (2:1, w/w) than with PC or PC:SM (2:1, w/w). Longer peptide (KW)5, but not (KW)3 or (KW)4, strongly bound and partially inserted into PC:CH compared to PC or PC:SM (2:1, w/w). Calcein release experiments showed that (KW)5 induced calcein leakage from the eukaryotic membrane. Greater calcein leakage was induced by (KW)5 from PC:CH than from PC:SM (2:1, w/w) or PC, whereas (KW)4 did not induce calcein leakage from any of the liposomes. Circular dichroism measurements indicated that (KW)5 showed higher conformational transition compared to (KW)4 due to peptide-liposome interactions. Taken together, our results suggest that (KW)5 reasonably mediates the aggregation and permeabilization of eukaryotic membranes, which could in turn explain why (KW)5 displays efficient hemolytic activity.
Keywords: (KW)5; hemolytic peptide; eukaryotic membrane; phosphatidylcholine; cholesterol; sphingomyelin; aggregation
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MDPI and ACS Style

Gopal, R.; Lee, J.K.; Lee, J.H.; Kim, Y.G.; Oh, G.C.; Seo, C.H.; Park, Y. Effect of Repetitive Lysine-Tryptophan Motifs on the Eukaryotic Membrane. Int. J. Mol. Sci. 2013, 14, 2190-2202.

AMA Style

Gopal R, Lee JK, Lee JH, Kim YG, Oh GC, Seo CH, Park Y. Effect of Repetitive Lysine-Tryptophan Motifs on the Eukaryotic Membrane. International Journal of Molecular Sciences. 2013; 14(1):2190-2202.

Chicago/Turabian Style

Gopal, Ramamourthy; Lee, Jong K.; Lee, Jun H.; Kim, Young G.; Oh, Gwang C.; Seo, Chang H.; Park, Yoonkyung. 2013. "Effect of Repetitive Lysine-Tryptophan Motifs on the Eukaryotic Membrane." Int. J. Mol. Sci. 14, no. 1: 2190-2202.

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