title: Fungicidal mechanisms of the antimicrobial peptide Bac8c.
abstract: Bac8c (RIWVIWRR-NH2) is an analogue peptide derived through complete substitution analysis of the linear bovine host defense peptide variant Bac2A. In the present study, the antifungal mechanism of Bac8c against pathogenic fungi was investigated, with a particular focus on the effects of Bac8c on the cytoplasmic membrane. We used bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)] staining and 3,3'-dipropylthiacarbocyanine iodide [DiSC3(5)] assays to show that Bac8c induced disturbances in the membrane potential of Candida albicans. An increase in membrane permeability and suppression of cell wall regeneration were also observed in Bac8c-treated C. albicans. We studied the effects of Bac8c treatment on model membranes to elucidate its antifungal mechanism. Using calcein and FITC-labeled dextran leakage assays from Bac8c-treated large unilamellar vesicles (LUVs) and giant unilamellar vesicles (GUVs), we found that Bac8c has a pore-forming action on fungal membranes, with an estimated pore radius of between 2.3 and 3.3 nm. A membrane-targeted mechanism of action was also supported by the observation of potassium release from the cytosol of Bac8c-treated C. albicans. These results indicate that Bac8c is considered as a potential candidate to develop a novel antimicrobial agent because of its low-cost production characteristics and high antimicrobial activity via its ability to induce membrane perturbations in fungi.
authors.affiliation: School of Life Sciences, BK 21 Plus KNU Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daehak-ro 80, Buk-gu, Daegu 702-701, Republic of Korea.
authors.forename: Wonyoung
authors.initials: W
authors.lastname: Lee
authors.affiliation: School of Life Sciences, BK 21 Plus KNU Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daehak-ro 80, Buk-gu, Daegu 702-701, Republic of Korea. Electronic address: dglee222@knu.ac.kr.
authors.forename: Dong Gun
authors.initials: DG
authors.lastname: Lee
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology*; D001463:Barbiturates; D052160:Benzothiazoles; D001692:Biological Transport / Q000187:drug effects; D002176:Candida albicans / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development; D002232:Carbocyanines; D002417:Cattle; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002473:Cell Wall / Q000737:chemistry / Q000187:drug effects; D003911:Dextrans; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007555:Isoxazoles; D008564:Membrane Potentials / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D011188:Potassium / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D053835:Unilamellar Liposomes / Q000737:chemistry
chemical_list: D000935:Antifungal Agents; D023181:Antimicrobial Cationic Peptides; D001463:Barbiturates; D052160:Benzothiazoles; D002232:Carbocyanines; D003911:Dextrans; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007555:Isoxazoles; D053835:Unilamellar Liposomes; C015219:fluorescein isothiocyanate dextran; C052795:bis(1,3-dibutylbarbiturate)trimethine oxonol; C012944:3,3'-dipropyl-2,2'-thiadicarbocyanine; D016650:Fluorescein-5-isothiocyanate; D011188:Potassium; C007740:fluorexon
keywords: Antifungal; Antimicrobial peptide; Bac8c; Candida albicans; Plasma membrane