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Decker T, Rautenbach M, Khan S, Khan W. Antibacterial efficacy and membrane mechanism of action of the Serratia-derived non-ionic lipopeptide, serrawettin W2-FL10. Microbiol Spectr 2024:e0295223. [PMID: 38842361 DOI: 10.1128/spectrum.02952-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 05/14/2024] [Indexed: 06/07/2024] Open
Abstract
The study aimed to investigate the antibacterial activity, cytotoxicity, and mechanism of action of the non-ionic, cyclic lipopeptide, serrawettin W2-FL10 against Staphylococcus aureus. W2-FL10 exhibited potent activity against the Gram-positive bacteria S. aureus, Enterococcus faecalis, Enterococcus faecium, Listeria monocytogenes, and Bacillus subtilis, with minimum inhibitory concentration (MIC) values ranging from 6.3 to 31.3 μg/mL, while no activity was observed against Gram-negative bacteria. Broth microdilution assays showed that W2-FL10 interacted with key cell membrane components, such as lipid phosphatidyl glycerol and lipoteichoic acid of S. aureus. Upon membrane interaction, W2-FL10 dissipated membrane potential within 12 min and increased S. aureus membrane permeability within 28-40 min, albeit at slower rates and higher concentrations than the lytic peptide melittin. The observed membrane permeability, as detected with propidium iodide (PI), may be attributed to transmembrane pores/lesions, possibly dependent on dimer-driven lipopeptide oligomerization in the membrane. Scanning electron microscopy (SEM) imaging also visually confirmed the formation of lesions in the cell wall of one of the S. aureus strains, and cell damage within 1 h of exposure to W2-FL10, corroborating the rapid time-kill kinetics of the S. aureus strains. This bactericidal action against the S. aureus strains corresponded to membrane permeabilization by W2-FL10, indicating that self-promoted uptake into the cytosol may be part of the mode of action. Finally, this lipopeptide exhibited low to moderate cytotoxicity to the Chinese hamster ovarian (CHO) cell line in comparison to the control (emetine) with an optimal lipophilicity range (log D value of 2.5), signifying its potential as an antibiotic candidate. IMPORTANCE Antimicrobial resistance is a major public health concern, urgently requiring antibacterial compounds exhibiting low adverse health effects. In this study, a novel antibacterial lipopeptide analog is described, serrawettin W2-FL10 (derived from Serratia marcescens), with potent activity displayed against Staphylococcus aureus. Mechanistic studies revealed that W2-FL10 targets the cell membrane of S. aureus, causing depolarization and permeabilization because of transmembrane lesions/pores, resulting in the leakage of intracellular components, possible cytosolic uptake of W2-FL10, and ultimately cell death. This study provides the first insight into the mode of action of a non-ionic lipopeptide. The low to moderate cytotoxicity of W2-FL10 also highlights its application as a promising therapeutic agent for the treatment of bacterial infections.
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Affiliation(s)
- Tanya Decker
- Water Health Research Centre, Faculty of Health Sciences, University of Johannesburg, Doornfontein, Johannesburg, Gauteng, South Africa
| | - Marina Rautenbach
- BioPep Peptide Group, Department of Biochemistry, Faculty of Science, Stellenbosch University, Stellenbosch, South Africa
| | - Sehaam Khan
- Water Health Research Centre, Faculty of Health Sciences, University of Johannesburg, Doornfontein, Johannesburg, Gauteng, South Africa
| | - Wesaal Khan
- Department of Microbiology, Faculty of Science, Stellenbosch University, Stellenbosch, South Africa
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2
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Guerinot C, Malige M, Charbonnel N, Malosse K, Jouffret L, Taillefumier C, Roy O, Forestier C, Faure S. Design of Triazolium-Grafted Peptidomimetic Macrocycles with Facial Amphipathicity to Target Pathogenic Bacteria. Org Lett 2024; 26:4088-4092. [PMID: 38709636 DOI: 10.1021/acs.orglett.4c01149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Access to 1,2,3-triazolium-grafted peptoid macrocycles was developed by macrocyclization and multivalent postmodification of linear peptoid oligomers carrying an alternance of benzylic and propargyl groups as side chains. X-ray analysis and NMR studies revealed a conformational preference for constrained hairpin-shaped structures leading to the facial amphipathic character of these macrocycles. A preliminary evaluation showed the antimicrobial activities of these new cationic amphipathic architectures.
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Affiliation(s)
- Cassandra Guerinot
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, ICCF, F-63000 Clermont-Ferrand, France
| | - Mélodie Malige
- Université Clermont Auvergne, CNRS, LMGE, F-63000 Clermont-Ferrand, France
| | - Nicolas Charbonnel
- Université Clermont Auvergne, CNRS, LMGE, F-63000 Clermont-Ferrand, France
| | - Killian Malosse
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, ICCF, F-63000 Clermont-Ferrand, France
| | - Laurent Jouffret
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, ICCF, F-63000 Clermont-Ferrand, France
| | - Claude Taillefumier
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, ICCF, F-63000 Clermont-Ferrand, France
| | - Olivier Roy
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, ICCF, F-63000 Clermont-Ferrand, France
| | | | - Sophie Faure
- Université Clermont Auvergne, Clermont Auvergne INP, CNRS, ICCF, F-63000 Clermont-Ferrand, France
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3
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Kumar V, van Rensburg W, Snoep JL, Paradies HH, Borrageiro C, de Villiers C, Singh R, Joshi KB, Rautenbach M. Antimicrobial nano-assemblies of tryptocidine C, a tryptophan-rich cyclic decapeptide, from ethanolic solutions. Biochimie 2023; 204:22-32. [PMID: 36057373 DOI: 10.1016/j.biochi.2022.08.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 08/02/2022] [Accepted: 08/26/2022] [Indexed: 01/12/2023]
Abstract
Tryptocidine C (TpcC), a Trp-rich cyclodecapeptide is a minor constituent in the antibiotic tyrothricin complex from Brevibacillus parabrevis. TpcC possesses a high tendency to oligomerise in aqueous solutions and dried TpcC forms distinct self-assembled nanoparticles. High-resolution scanning electron microscopy revealed the influence of different ethanol:water solvent systems on TpcC self-assembly, with the TpcC, dried from a high concentration in 15% ethanol, primarily assembling into small nanospheres with 24.3 nm diameter and 0.05 polydispersity. TpcC at 16 μM, near its CMC, formed a variety of structures such as small nanospheres, large dense nanospheroids and facetted 3-D-crystals, as well as sheets and coarse carpet-like structures which depended on ethanol concentration. Drying 16 μM TpcC from 75% ethanol resulted in highly facetted 3-D crystals, as well as small nanospheres, while those in 10% ethanol preparation had less defined facets. Drying from 20 to 50% ethanol led to polymorphic architectures with a few defined nanospheroids and various small nanoparticles, imbedded in carpet- and sheet-like structures. These polymorphic surface morphologies correlated with maintenance of fluorescence properties and the surface-derived antibacterial activity against Staphylococcus aureus over time, while there was a significant change in fluorescence and loss in activity in the 10% and 75% preparations where 3-D crystals were observed. This indicated that TpcC oligomerisation in solutions with 20-50% ethanol leads to metastable structures with a high propensity for release of antimicrobial moieties, while those leading to crystallisation limit active moieties release. TpcC nano-assemblies can find application in antimicrobial coatings, surface disinfectants, food packaging and wound healing materials.
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Affiliation(s)
- Vikas Kumar
- Department of Biochemistry, Stellenbosch University, Stellenbosch, 7600, South Africa
| | - Wilma van Rensburg
- Department of Biochemistry, Stellenbosch University, Stellenbosch, 7600, South Africa
| | - Jacky L Snoep
- Department of Biochemistry, Stellenbosch University, Stellenbosch, 7600, South Africa; Molecular Cell Biology, Vrije Universiteit Amsterdam, De Boelelaan 1105, 1081 HV, Amsterdam, the Netherlands
| | - Henrich H Paradies
- Jacobs-University, Department of Chemistry and Life Science, Bremen, 30110, Germany
| | | | - Carmen de Villiers
- Department of Biochemistry, Stellenbosch University, Stellenbosch, 7600, South Africa
| | - Ramesh Singh
- Department of Chemistry, Dr Harisingh Gour Vishwavidyalaya (A Central University), Sagar, MP, 470003, India
| | - Khashti Ballabh Joshi
- Department of Chemistry, Dr Harisingh Gour Vishwavidyalaya (A Central University), Sagar, MP, 470003, India
| | - Marina Rautenbach
- Department of Biochemistry, Stellenbosch University, Stellenbosch, 7600, South Africa.
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4
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van Rensburg W, Rautenbach M. Creating Robust Antimicrobial Materials with Sticky Tyrocidines. Antibiotics (Basel) 2022; 11:antibiotics11020174. [PMID: 35203778 PMCID: PMC8868332 DOI: 10.3390/antibiotics11020174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/22/2022] [Accepted: 01/24/2022] [Indexed: 12/10/2022] Open
Abstract
Modified antimicrobial and antifouling materials and surfaces can be used to limit the propagation of microorganisms on various surfaces and minimise the occurrence of infection, transfer, and spoilage. Increased demand for ‘green’ solutions for material treatment has pushed the focus towards to naturally produced antimicrobials. Tyrocidines, cyclo-decapeptides naturally produced by a soil bacterium Brevibacillus parabrevis, have a broad spectrum of activity against Gram-positive and Gram-negative bacteria, filamentous fungi, and yeasts. Continual losses in tyrocidine production highlighted the possible association of peptides to surfaces. It was found in this study that tyrocidines readily associates with many materials, with a selectivity towards polysaccharide-type materials, such as cellulose. Peptide-treated cellulose was found to remain active after exposure to a broad pH range, various temperatures, salt solutions, water washes, and organic solvents, with the sterilising activity only affected by 1% SDS and 70% acetonitrile. Furthermore, a comparison to other antimicrobial peptides showed the association between tyrocidines and cellulose to be unique in terms of antimicrobial activity. The robust association between the tyrocidines and various materials holds great promise in applications focused on preventing surface contamination and creating self-sterilising materials.
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Just‐Baringo X, Yeste‐Vázquez A, Moreno‐Morales J, Ballesté‐Delpierre C, Vila J, Giralt E. Controlling Antibacterial Activity Exclusively with Visible Light: Introducing a Tetra-ortho-Chloro-Azobenzene Amino Acid. Chemistry 2021; 27:12987-12991. [PMID: 34227716 PMCID: PMC8518743 DOI: 10.1002/chem.202102370] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Indexed: 11/30/2022]
Abstract
The introduction of a novel tetra-ortho-chloroazobenzene amino acid (CEBA) has enabled photoswitching of the antimicrobial activity of tyrocidine A analogues by using exclusively visible light, granting spatiotemporal control under benign conditions. Compounds bearing this photoswitchable amino acid become active upon irradiation with red light, but quickly turn-off upon exposure to other visible light wavelengths. Critically, sunlight quickly triggers isomerisation of the red light-activated compounds into their original trans form, offering an ideal platform for self-deactivation upon release into the environment. Linear analogues of tyrocidine A were found to provide the best photocontrol of their antimicrobial activity, leading to compounds active against Acinetobacter baumannii upon isomerisation. Exploration of their N- and C-termini has provided insights into key elements of their structure and has allowed obtaining new antimicrobials displaying excellent strain selectivity and photocontrol.
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Affiliation(s)
- Xavier Just‐Baringo
- Institute for Research in Biomedicine (IRB Barcelona)Barcelona Institute of Science and Technology (BIST)Baldiri Reixac 1008028BarcelonaSpain
- Laboratori de Química OrgànicaFacultat de FarmàciaIBUBUniversitat de Barcelona08028BarcelonaSpain
| | - Alejandro Yeste‐Vázquez
- Institute for Research in Biomedicine (IRB Barcelona)Barcelona Institute of Science and Technology (BIST)Baldiri Reixac 1008028BarcelonaSpain
| | - Javier Moreno‐Morales
- Institute for Global Health (ISGlobal)Hospital Clínic - Universitat de BarcelonaBarcelonaSpain
| | | | - Jordi Vila
- Institute for Global Health (ISGlobal)Hospital Clínic - Universitat de BarcelonaBarcelonaSpain
- Department of Clinical Microbiology – CDBHospital Clínic - University of BarcelonaBarcelonaSpain
| | - Ernest Giralt
- Institute for Research in Biomedicine (IRB Barcelona)Barcelona Institute of Science and Technology (BIST)Baldiri Reixac 1008028BarcelonaSpain
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Vaca J, Ortiz A, Sansinenea E. Bacillus sp. Bacteriocins: Natural Weapons against Bacterial Enemies. Curr Med Chem 2021; 29:2093-2108. [PMID: 34047258 DOI: 10.2174/0929867328666210527093041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 04/08/2021] [Accepted: 04/13/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND Currently, antibiotic-resistant pathogenic bacteria are emerging as an important health problem worldwide. The search for new compounds with antibiotic characteristics is the most promising alternative. Bacteriocins are natural compounds that are inhibitory against pathogens, and Bacillus species are the major producers of these compounds, which have shown antimicrobial activity against clinically important bacteria. These peptides not only have potential in the pharmaceutical industry but also in food and agricultural sectors. OBJECTIVE We provide an overview of the recent bacteriocins isolated from different species of Bacillus including their applications and the older bacteriocins. RESULTS In this review, we have revised some works about the improvements carried out in the production of bacteriocins. CONCLUSION These applications make bacteriocins very promising compounds that need to study for industrial production.
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Affiliation(s)
- Jessica Vaca
- Facultad De Ciencias Químicas, Benemérita Universidad Autónoma De Puebla, 72590 Puebla; Pue, Mexico
| | - Aurelio Ortiz
- Facultad De Ciencias Químicas, Benemérita Universidad Autónoma De Puebla, 72590 Puebla; Pue, Mexico
| | - Estibaliz Sansinenea
- Facultad De Ciencias Químicas, Benemérita Universidad Autónoma De Puebla, 72590 Puebla; Pue, Mexico
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7
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Masoudi Y, van Rensburg W, Barnard-Jenkins B, Rautenbach M. The Influence of Cellulose-Type Formulants on Anti- Candida Activity of the Tyrocidines. Antibiotics (Basel) 2021; 10:antibiotics10050597. [PMID: 34069885 PMCID: PMC8157355 DOI: 10.3390/antibiotics10050597] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 04/18/2021] [Accepted: 04/21/2021] [Indexed: 11/16/2022] Open
Abstract
Candida species are highly adaptable to environmental changes with their phenotypic flexibility allowing for the evasion of most host defence mechanisms. Moreover, increasing resistance of human pathogenic Candida strains has been reported against all four classes of available antifungal drugs, which highlights the need for combinational therapies. Tyrocidines are cyclic antimicrobial peptides that have shown synergistic activity with antifungal drugs such as caspofungin and amphotericin B. However, these cyclodecapeptides have haemolytic activity and cytotoxicity, but they have been used for decades in the clinic for topical applications. The tyrocidines tend to form higher-order structures in aqueous solutions and excessive aggregation can result in variable or diminished activity. Previous studies have shown that the tyrocidines prefer ordered association to celluloses. Therefore, a formulation with soluble cellulose was used to control the oligomer stability and size, thereby increasing the activity against Candida spp. Of the formulants tested, it was found that commercial hydroxy-propyl-methyl cellulose, E10M, yielded the best results with increased stability, increased anti-Candida activity, and improved selectivity. This formulation holds promise in topical applications against Candida spp. infections.
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Zhu J, Hu C, Zeng Z, Deng X, Zeng L, Xie S, Fang Y, Jin Y, Alezra V, Wan Y. Polymyxin B-inspired non-hemolytic tyrocidine A analogues with significantly enhanced activity against gram-negative bacteria: How cationicity impacts cell specificity and antibacterial mechanism. Eur J Med Chem 2021; 221:113488. [PMID: 33991963 DOI: 10.1016/j.ejmech.2021.113488] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 03/31/2021] [Accepted: 04/18/2021] [Indexed: 11/25/2022]
Abstract
Naturally occurring cyclic antimicrobial peptides (AMPs) such as tyrocidine A (Tyrc A) and gramicidin S (GS) are appealing targets for the development of novel antibiotics. However, their therapeutic potentials are limited by undesired hemolytic activity and relatively poor activity against Gram-negative bacteria. Inspired by polycationic lipopeptide polymyxin B (PMB), the so called 'last-resort' antibiotic for the treatment of infections caused by multidrug-resistant Gram-negative bacteria, we synthesized and biologically evaluated a series of polycationic analogues derived from Tyrc A. We were able to obtain peptide 8 that possesses 5 positive charges exhibiting potent activities against both Gram-negative and Gram-positive bacteria along with totally diminished hemolytic activity. Intriguingly, antibacterial mechanism studies revealed that, rather than the 'pore forming' model that possessed by Tyrc A, peptide 8 likely diffuses membrane in a 'detergent-like' manner. Furthermore, when treating mice with peritonitis-sepsis, peptide 8 showed excellent antibacterial and anti-inflammatory activities in vivo.
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Affiliation(s)
- Jibao Zhu
- National Pharmaceutical Engineering Center for Solid Preparation in Chinese Herbal Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China
| | - Chengfei Hu
- National Pharmaceutical Engineering Center for Solid Preparation in Chinese Herbal Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China
| | - Zizhen Zeng
- National Pharmaceutical Engineering Center for Solid Preparation in Chinese Herbal Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China
| | - Xiaoyu Deng
- Minist Educ, Key Lab Modern Preparat TCM, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China
| | - Lingbing Zeng
- Department of Clinical Laboratory, The First Affiliated Hospital of Nanchang University, 17 Yongwaizheng Street, Donghu, Nanchang, 330006, PR China
| | - Saisai Xie
- National Pharmaceutical Engineering Center for Solid Preparation in Chinese Herbal Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China
| | - Yuanying Fang
- National Pharmaceutical Engineering Center for Solid Preparation in Chinese Herbal Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China
| | - Yi Jin
- National Pharmaceutical Engineering Center for Solid Preparation in Chinese Herbal Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China
| | - Valérie Alezra
- Laboratoire de Méthodologie, Synthèse et Molécules Thérapeutiques (ICMMO), UMR 8182, CNRS, Université Paris-Saclay, Bât 410, Facultédes Sciences D'Orsay, Orsay, 291405, France
| | - Yang Wan
- National Pharmaceutical Engineering Center for Solid Preparation in Chinese Herbal Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, PR China; Laboratoire de Méthodologie, Synthèse et Molécules Thérapeutiques (ICMMO), UMR 8182, CNRS, Université Paris-Saclay, Bât 410, Facultédes Sciences D'Orsay, Orsay, 291405, France; State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Guangxi Normal University, 15 Yuchai Road, Guilin, 541004, PR China.
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9
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Rautenbach M, Kumar V, Vosloo JA, Masoudi Y, van Wyk RJ, Stander MA. Oligomerisation of tryptocidine C, a Trp-rich cyclodecapeptide from the antimicrobial tyrothricin complex. Biochimie 2020; 181:123-133. [PMID: 33333170 DOI: 10.1016/j.biochi.2020.12.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 11/17/2020] [Accepted: 12/12/2020] [Indexed: 01/07/2023]
Abstract
Tryptocidine C (TpcC, cyclo[D-Phe1-Pro2-Trp3-D-Trp4-Asn5-Gln6-Trp7-Val8-Orn9-Leu10]) is a broad-spectrum antimicrobial peptide in the tyrothricin complex produced by a soil bacterium, Brevibacillus parabrevis. Electrospray mass spectrometric studies reveal the oligomerisation of TpcC into dimers and higher oligomers, analogous to tyrocidine C (TrcC, Trp7 replaced by Tyr7). Ion mobility mass spectrometry (IMMS) further confirms the formation of stable peptide dimers and tetramers with diameters of 2.7 nm and 3.3 nm, respectively, calculated from collisional cross section (CCS). Molecular dynamic simulations and docking studies support the formation of amphipathic dimers, with a diameter of 2.5 ± 0.07 nm calculated from low energy model CCS. Circular dichroism and IMMS studies point towards dynamic hydrogen-bonded conformational changes up to 28-33 μM after which the structures become more static (or in equilibrium). Fluorescence studies indicate aromatic stacking of Trp residues with a CMC of 18 μM in aqueous solutions. The concentration and time dependent interaction of Trp in oligomers indicate cooperativity in the TpcC oligomerisation that leads to the formation of higher order microscopic structures. Scanning electron microscopy studies unequivocally shows that TpcC forms nanospheres with a mean diameter of 25 nm. Repeated smaller oligomeric units, possibly dimers and tetramers, self-assemble to form these nanospheres.
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Affiliation(s)
- Marina Rautenbach
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa.
| | - Vikas Kumar
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa.
| | - J Arnold Vosloo
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa
| | - Yasamin Masoudi
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa
| | - Rosalind J van Wyk
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa
| | - Marietjie A Stander
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa; LC-MS Unit of the Central Analytical Facility, Stellenbosch University, Stellenbosch, South Africa
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10
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Jokonya S, Langlais M, Leshabane M, Reader PW, Vosloo JA, Pfukwa R, Coertzen D, Birkholtz LM, Rautenbach M, Klumperman B. Poly( N-vinylpyrrolidone) Antimalaria Conjugates of Membrane-Disruptive Peptides. Biomacromolecules 2020; 21:5053-5066. [PMID: 33156615 DOI: 10.1021/acs.biomac.0c01202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The concepts of polymer-peptide conjugation and self-assembly were applied to antimicrobial peptides (AMPs) in the development of a targeted antimalaria drug delivery construct. This study describes the synthesis of α-acetal, ω-xanthate heterotelechelic poly(N-vinylpyrrolidone) (PVP) via reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization, followed by postpolymerization deprotection to yield α-aldehyde, ω-thiol heterotelechelic PVP. A specific targeting peptide, GSRSKGT, for Plasmodium falciparum-infected erythrocytes was used to sparsely decorate the α-chain ends via reductive amination while cyclic decapeptides from the tyrocidine group were conjugated to the ω-chain end via thiol-ene Michael addition. The resultant constructs were self-assembled into micellar nanoaggregates whose sizes and morphologies were determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The in vitro activity and selectivity of the conjugates were evaluated against intraerythrocytic P. falciparum parasites.
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Affiliation(s)
- Simbarashe Jokonya
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Marvin Langlais
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Meta Leshabane
- Department of Biochemistry, Genetics and Microbiology, Institute of Sustainable Malaria Control, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Paul W Reader
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Johan A Vosloo
- BioPep Peptide Group, Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Rueben Pfukwa
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Dina Coertzen
- Department of Biochemistry, Genetics and Microbiology, Institute of Sustainable Malaria Control, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Lyn-Marie Birkholtz
- Department of Biochemistry, Genetics and Microbiology, Institute of Sustainable Malaria Control, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Marina Rautenbach
- BioPep Peptide Group, Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Bert Klumperman
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
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Abstract
Despite efforts to develop new antibiotics, antibacterial resistance still develops too fast for drug discovery to keep pace. Often, resistance against a new drug develops even before it reaches the market. This continued resistance crisis has demonstrated that resistance to antibiotics with single protein targets develops too rapidly to be sustainable. Most successful long-established antibiotics target more than one molecule or possess targets, which are encoded by multiple genes. This realization has motivated a change in antibiotic development toward drug candidates with multiple targets. Some mechanisms of action presuppose multiple targets or at least multiple effects, such as targeting the cytoplasmic membrane or the carrier molecule bactoprenol phosphate and are therefore particularly promising. Moreover, combination therapy approaches are being developed to break antibiotic resistance or to sensitize bacteria to antibiotic action. In this Review, we provide an overview of antibacterial multitarget approaches and the mechanisms behind them.
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Affiliation(s)
- Declan Alan Gray
- Newcastle University
Biosciences Institute, Newcastle University, NE2 4HH Newcastle
upon Tyne, United Kingdom
| | - Michaela Wenzel
- Division of Chemical
Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden
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12
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Borges A, Gillespie D, Nag A. Biological applications of amide and amino acid containing synthetic macrocycles. Supramol Chem 2019. [DOI: 10.1080/10610278.2019.1650178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Ariane Borges
- Department of Chemistry, Clark University, Worcester, MA, USA
| | - Dylan Gillespie
- Department of Chemistry, Clark University, Worcester, MA, USA
| | - Arundhati Nag
- Department of Chemistry, Clark University, Worcester, MA, USA
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13
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Juhl DW, van Rensburg W, Bossis X, Vosloo JA, Rautenbach M, Bechinger B. Tyrocidine A interactions with saccharides investigated by CD and NMR spectroscopies. J Pept Sci 2019; 25:e3163. [PMID: 30884009 DOI: 10.1002/psc.3163] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 02/10/2019] [Accepted: 02/12/2019] [Indexed: 01/23/2023]
Abstract
Tyrocidines are a family of cyclic decapeptides produced by the soil bacterium, Brevibacillus parabrevis. These antibiotic peptides can be used to prevent infections in agriculture and food industry but also to prepare antimicrobial lozenges, creams, and dressings for medical applications. It has been observed that the tyrocidines interact with saccharides such as cellulose from their soil environment, as well as sugars in culture media and glycans in fungal cell walls. Here, we investigated the interactions of tyrocidines with glucose, sucrose, and cellotetraose (as cellulose model) in a quantitative fashion utilising CD and NMR spectroscopy. The CD and NMR spectra of tyrocidine A (TrcA) were analysed as a function of solvent composition, and the spectral properties agree with the formation of oligomeric structures that are governed by β-sheet secondary structures once the acetonitrile content of the solvent is increased. Saccharides seem to also induce TrcA spectral changes reverting those induced by organic solvents. The CD spectral changes of TrcA in the presence of glucose agree with new ordered H-bonding, possibly β-sheet structures. The amides involved in intramolecular H-bonding remained largely unaffected by the environmental changes. In contrast, amides exposed to the exterior and/or involved in TrcA intermolecular association show the largest 1 H chemical shift changes. CD and NMR spectroscopic investigations correlated well with TrcA-glucose interactions characterized by a dissociation constant around 200 μM. Interestingly, the association of cellotetraose corresponds closely to the additive effect from four glucose moieties, while a much higher dissociation constant was observed for sucrose. Similar trends to TrcA for binding to the three saccharides were observed for the analogous tyrocidines, tyrocidine B, and tyrocidine C. These results therefore indicate that the tyrocidine interactions with the glucose monosaccharide unit are fairly specific and reversible.
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Affiliation(s)
| | - Wilma van Rensburg
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, Matieland, South Africa
| | | | - J Arnold Vosloo
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, Matieland, South Africa
| | - Marina Rautenbach
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, Matieland, South Africa
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14
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The Multifaceted Antibacterial Mechanisms of the Pioneering Peptide Antibiotics Tyrocidine and Gramicidin S. mBio 2018; 9:mBio.00802-18. [PMID: 30301848 PMCID: PMC6178620 DOI: 10.1128/mbio.00802-18] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Cyclic β-sheet decapeptides, such as tyrocidines and gramicidin S, were among the first antibiotics in clinical application. Although they have been used for such a long time, there is virtually no resistance to them, which has led to a renewed interest in this peptide class. Both tyrocidines and gramicidin S are thought to disrupt the bacterial membrane. However, this knowledge is mainly derived from in vitro studies, and there is surprisingly little knowledge about how these long-established antibiotics kill bacteria. Our results shed new light on the antibacterial mechanism of β-sheet peptide antibiotics and explain why they are still so effective and why there is so little resistance to them. Cyclic β-sheet decapeptides from the tyrocidine group and the homologous gramicidin S were the first commercially used antibiotics, yet it remains unclear exactly how they kill bacteria. We investigated their mode of action using a bacterial cytological profiling approach. Tyrocidines form defined ion-conducting pores, induce lipid phase separation, and strongly reduce membrane fluidity, resulting in delocalization of a broad range of peripheral and integral membrane proteins. Interestingly, they also cause DNA damage and interfere with DNA-binding proteins. Despite sharing 50% sequence identity with tyrocidines, gramicidin S causes only mild lipid demixing with minor effects on membrane fluidity and permeability. Gramicidin S delocalizes peripheral membrane proteins involved in cell division and cell envelope synthesis but does not affect integral membrane proteins or DNA. Our results shed a new light on the multifaceted antibacterial mechanisms of these antibiotics and explain why resistance to them is virtually nonexistent.
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15
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Antimicrobial peptides produced by Brevibacillus spp.: structure, classification and bioactivity: a mini review. World J Microbiol Biotechnol 2018; 34:57. [DOI: 10.1007/s11274-018-2437-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 03/22/2018] [Indexed: 10/17/2022]
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16
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Cameron AJ, Edwards PJB, Harjes E, Sarojini V. Tyrocidine A Analogues Bearing the Planar d-Phe-2-Abz Turn Motif: How Conformation Impacts Bioactivity. J Med Chem 2017; 60:9565-9574. [DOI: 10.1021/acs.jmedchem.7b00953] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Alan J. Cameron
- School
of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Patrick J. B. Edwards
- Institute
of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Elena Harjes
- Institute
of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
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17
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Zhu M, Liu P, Niu ZW. A perspective on general direction and challenges facing antimicrobial peptides. CHINESE CHEM LETT 2017. [DOI: 10.1016/j.cclet.2016.10.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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18
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Wen G, Qin W, Chen D, Wang Y, Yue X, Liu Z, Cao Y, Du J, Zhou B, Bu X. Stabilizing the monomeric amyloid-β peptide by tyrocidine A prevents and reverses amyloidogenesis without the accumulation of oligomers. Chem Commun (Camb) 2017; 53:3886-3889. [DOI: 10.1039/c7cc00506g] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Stabilizing the monomeric amyloid-β peptide by tyrocidine A prevents accumulation of oligomers.
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Affiliation(s)
- Gesi Wen
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Wenjing Qin
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Daoyuan Chen
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Youqiao Wang
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Xin Yue
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Ziyi Liu
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Yingnan Cao
- Department of Pharmacology
- Xinhua College of Sun Yat-sen University
- Guangzhou
- P. R. China
| | - Jun Du
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Binhua Zhou
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Xianzhang Bu
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
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19
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Rautenbach M, Troskie AM, Vosloo JA, Dathe ME. Antifungal membranolytic activity of the tyrocidines against filamentous plant fungi. Biochimie 2016; 130:122-131. [DOI: 10.1016/j.biochi.2016.06.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Accepted: 06/15/2016] [Indexed: 12/11/2022]
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20
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Rautenbach M, Troskie AM, Vosloo JA. Antifungal peptides: To be or not to be membrane active. Biochimie 2016; 130:132-145. [PMID: 27234616 DOI: 10.1016/j.biochi.2016.05.013] [Citation(s) in RCA: 123] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 05/20/2016] [Indexed: 02/06/2023]
Abstract
Most antifungal peptides (AFPs), if not all, have membrane activity, while some also have alternative targets. Fungal membranes share many characteristics with mammalian membranes with only a few differences, such as differences in sphingolipids, phosphatidylinositol (PI) content and the main sterol is ergosterol. Fungal membranes are also more negative and a better target for cationic AFPs. Targeting just the fungal membrane lipids such as phosphatidylinositol and/or ergosterol by AFPs often translates into mammalian cell toxicity. Conversely, a specific AFP target in the fungal pathogen, such as glucosylceramide, mannosyldiinositol phosphorylceramide or a fungal protein target translates into high pathogen selectivity. However, a lower target concentration, absence or change in the specific fungal target can naturally lead to resistance, although such resistance in turn could result in reduced pathogen virulence. The question is then to be or not to be membrane active - what is the best choice for a successful AFP? In this review we deliberate on this question by focusing on the recent advances in our knowledge on how natural AFPs target fungi.
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Affiliation(s)
- Marina Rautenbach
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, South Africa.
| | - Anscha M Troskie
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, South Africa
| | - J Arnold Vosloo
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, South Africa
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21
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Struck AW, Bennett MR, Shepherd SA, Law BJC, Zhuo Y, Wong LS, Micklefield J. An Enzyme Cascade for Selective Modification of Tyrosine Residues in Structurally Diverse Peptides and Proteins. J Am Chem Soc 2016; 138:3038-45. [DOI: 10.1021/jacs.5b10928] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Anna-Winona Struck
- School of Chemistry and Manchester
Institute of Biotechnology, The University of Manchester, 131 Princess
Street, Manchester M1 7DN, United Kingdom
| | - Matthew R. Bennett
- School of Chemistry and Manchester
Institute of Biotechnology, The University of Manchester, 131 Princess
Street, Manchester M1 7DN, United Kingdom
| | - Sarah A. Shepherd
- School of Chemistry and Manchester
Institute of Biotechnology, The University of Manchester, 131 Princess
Street, Manchester M1 7DN, United Kingdom
| | - Brian J. C. Law
- School of Chemistry and Manchester
Institute of Biotechnology, The University of Manchester, 131 Princess
Street, Manchester M1 7DN, United Kingdom
| | - Ying Zhuo
- School of Chemistry and Manchester
Institute of Biotechnology, The University of Manchester, 131 Princess
Street, Manchester M1 7DN, United Kingdom
| | - Lu Shin Wong
- School of Chemistry and Manchester
Institute of Biotechnology, The University of Manchester, 131 Princess
Street, Manchester M1 7DN, United Kingdom
| | - Jason Micklefield
- School of Chemistry and Manchester
Institute of Biotechnology, The University of Manchester, 131 Princess
Street, Manchester M1 7DN, United Kingdom
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22
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Troskie AM, de Beer A, Vosloo JA, Jacobs K, Rautenbach M. Inhibition of agronomically relevant fungal phytopathogens by tyrocidines, cyclic antimicrobial peptides isolated from Bacillus aneurinolyticus. Microbiology (Reading) 2014; 160:2089-2101. [DOI: 10.1099/mic.0.078840-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The tyrocidines, a complex of analogous cyclic decapeptides produced by Bacillus aneurinolyticus, exhibited noteworthy activity against a range of phytopathogenic fungi, including Fusarium verticillioides, Fusarium solani and Botrytis cinerea. The activity of the tyrocidine peptide complex (Trc mixture) and purified tyrocidines exhibited minimum inhibition concentrations below 13 µg ml−1 (~10 µM) and was significantly more potent than that of the commercial imidazole fungicide, bifonazole. Although the tyrocidines’ activity was negatively influenced by the presence of Ca2+, it remained unaffected by the presence of Mg2+, Na+ and K+. Microscopic analysis revealed significant impact on the morphology of F. solani and Bot. cinerea including retarded germination and hyperbranching of hyphae. Studies with membrane-impermeable dyes, SYTOX green and propidium iodide suggested that the main mode of action of tyrocidines involves the disruption of fungal membrane integrity. Because of the tyrocidines’ broad spectrum and potent antifungal activity, possible multiple targets reducing the risk of overt resistance and general salt tolerance, they are promising candidates that warrant further investigation as bio-fungicides.
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Affiliation(s)
- Anscha M. Troskie
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland 7600, South Africa
| | - Abré de Beer
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland 7600, South Africa
| | - Johan A. Vosloo
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland 7600, South Africa
| | - Karin Jacobs
- Department of Microbiology, University of Stellenbosch, Private Bag X1, Matieland 7600, South Africa
| | - Marina Rautenbach
- BIOPEP Peptide Group, Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland 7600, South Africa
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23
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Leussa ANN, Rautenbach M. Detailed SAR and PCA of the Tyrocidines and Analogues Towards Leucocin A-Sensitive and Leucocin A-ResistantListeria monocytogenes. Chem Biol Drug Des 2014; 84:543-57. [DOI: 10.1111/cbdd.12344] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 03/22/2014] [Accepted: 04/15/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Adrienne Nyango-Nkeh Leussa
- BIOPEP Peptide Group; Department of Biochemistry; University of Stellenbosch; Private Bag X1 Matieland, 7602 Stellenbosch South Africa
| | - Marina Rautenbach
- BIOPEP Peptide Group; Department of Biochemistry; University of Stellenbosch; Private Bag X1 Matieland, 7602 Stellenbosch South Africa
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24
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Synergistic activity of the tyrocidines, antimicrobial cyclodecapeptides from Bacillus aneurinolyticus, with amphotericin B and caspofungin against Candida albicans biofilms. Antimicrob Agents Chemother 2014; 58:3697-707. [PMID: 24752256 DOI: 10.1128/aac.02381-14] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Tyrocidines are cationic cyclodecapeptides from Bacillus aneurinolyticus that are characterized by potent antibacterial and antimalarial activities. In this study, we show that various tyrocidines have significant activity against planktonic Candida albicans in the low-micromolar range. These tyrocidines also prevented C. albicans biofilm formation in vitro. Studies with the membrane-impermeable dye propidium iodide showed that the tyrocidines disrupt the membrane integrity of mature C. albicans biofilm cells. This membrane activity correlated with the permeabilization and rapid lysis of model fungal membranes containing phosphatidylcholine and ergosterol (70:30 ratio) induced by the tyrocidines. The tyrocidines exhibited pronounced synergistic biofilm-eradicating activity in combination with two key antifungal drugs, amphotericin B and caspofungin. Using a Caenorhabditis elegans infection model, we found that tyrocidine A potentiated the activity of caspofungin. Therefore, tyrocidines are promising candidates for further research as antifungal drugs and as agents for combinatorial treatment.
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25
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Loll PJ, Upton EC, Nahoum V, Economou NJ, Cocklin S. The high resolution structure of tyrocidine A reveals an amphipathic dimer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1199-207. [PMID: 24530898 DOI: 10.1016/j.bbamem.2014.01.033] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 01/20/2014] [Accepted: 01/27/2014] [Indexed: 11/28/2022]
Abstract
Tyrocidine A, one of the first antibiotics ever to be discovered, is a cyclic decapeptide that binds to membranes of target bacteria, disrupting their integrity. It is active against a broad spectrum of Gram-positive organisms, and has recently engendered interest as a potential scaffold for the development of new drugs to combat antibiotic-resistant pathogens. We present here the X-ray crystal structure of tyrocidine A at a resolution of 0.95Å. The structure reveals that tyrocidine forms an intimate and highly amphipathic homodimer made up of four beta strands that associate into a single, highly curved antiparallel beta sheet. We used surface plasmon resonance and potassium efflux assays to demonstrate that tyrocidine binds tightly to mimetics of bacterial membranes with an apparent dissociation constant (K(D)) of 10 μM, and efficiently permeabilizes bacterial cells at concentrations equal to and below the K(D). Using variant forms of tyrocidine in which the fluorescent probe p-cyano-phenylalanine had been inserted on either the polar or apolar face of the molecule, we performed fluorescence quenching experiments, using both water-soluble and membrane-embedded quenchers. The quenching results, together with the structure, strongly support a membrane association model in which the convex, apolar face of tyrocidine's beta sheet is oriented toward the membrane interior, while the concave, polar face is presented to the aqueous phase.
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Affiliation(s)
- Patrick J Loll
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
| | - Elizabeth C Upton
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Virginie Nahoum
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Nicoleta J Economou
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Simon Cocklin
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
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