Synthesis, biophysical and functional studies of two BP100 analogues modified by a hydrophobic chain and a cyclic peptide

Gustavo P.B. Carretero, Greice K.V. Saraiva, Ana C.G. Cauz, Magali A. Rodrigues, Sumika Kiyota, Karin A. Riske, Alcindo A. dos Santos, Marcos F. Pinatto-Botelho, Marcelo P. Bemquerer, Frederico J. Gueiros-Filho, Hernan Chaimovich, Shirley Schreier, Iolanda M. Cuccovia*

*Corresponding author

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Abstract

Antimicrobial peptides (AMPs) work as a primary defense against pathogenic microorganisms. BP100, (KKLFKKILKYL-NH 2 ), a rationally designed short, highly cationic AMP, acts against many bacteria, displaying low toxicity to eukaryotic cells. Previously we found that its mechanism of action depends on membrane surface charge and on peptide-to-lipid ratio. Here we present the synthesis of two BP100 analogs: BP100‑alanyl‑hexadecyl‑1‑amine (BP100-Ala-NH-C 16 H 33 ) and cyclo(1‑4)‑D‑Cys 1 , Ile 2 , Leu 3 , Cys 4 -BP100 (Cyclo(1‑4)‑cILC-BP100). We examined their binding to large unilamellar vesicles (LUV), conformational and functional properties, and compared with those of BP100. The analogs bound to membranes with higher affinity and a lesser dependence on electrostatic forces than BP100. In the presence of LUV, BP100 and BP100-Ala-NH-C 16 H 33 acquired α-helical conformation, while Cyclo(1‑4)‑cILC-BP100) was partly α-helical and partly β-turn. Taking in conjunction: 1. particle sizes and zeta potential, 2. effects on lipid flip-flop, 3. leakage of LUVs internal contents, and 4. optical microscopy of giant unilamellar vesicles, we concluded that at high concentrations, all three peptides acted by a carpet mechanism, while at low concentrations the peptides acted by disorganizing the lipid bilayer, probably causing membrane thinning. The higher activity and lesser membrane surface charge dependence of the analogs was probably due to their greater hydrophobicity. The MIC values of both analogs towards Gram-positive and Gram-negative bacteria were similar to those of BP100 but both analogues were more hemolytic. Confocal microscopy showed Gram-positive B. subtilis killing with concomitant extensive membrane damage suggestive of lipid clustering, or peptide-lipid aggregation. These results were in agreement with those found in model membranes.
OriginalsprogEngelsk
TidsskriftBiochimica et Biophysica Acta - Biomembranes
Vol/bind1860
Udgave nummer8
Sider (fra-til)1502-1516
Antal sider15
ISSN0005-2736
DOI
StatusUdgivet - aug. 2018

Bibliografisk note

Funding Information:
Authors are recipients of the following fellowships: Gustavo P. B. Carretero: INCT-FCx CAPES post-doctoral fellowship (88887.137085/2017-00), Greice K.V. Saraiva: Proj. Biocomputacional CAPES post-doctoral fellowship (23038.004630/2017-35), Ana C.G. Cauz: CAPES PhD fellowship. Marcos Felipe Pinatto-Botelho: CNPq PhD fellowship (141779/2014-4). Karin A. Riske, Shirley Schreier, Marcelo P. Bemquerer, Frederico J. Gueiros-Filho, Hernan Chaimovich and Iolanda M. Cuccovia are CNPq research fellows. The authors acknowledge graduate student Peter Park for the Graphical Abstract.

Funding Information:
The following funding agencies are acknowledged: FAPESP ( 2013/08166-5 ); National Council for Scientific and Technological Development (CNPq – 465259/2014-6 ), the Coordination for the Improvement of Higher Education Personnel (CAPES), the National Institute of Science and Technology Complex Fluids (INCT-FCx), and the São Paulo Research Foundation (FAPESP – 2014/50983-3 ). Núcleo de Apoio à Pesquisa de Fluidos Complexos, NAP-FCx.

Emneord

  • Antimicrobial peptides
  • BP100 analogs
  • Mechanism of action
  • Spectroscopy
  • Structure-activity relationship

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