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Sharma P, Vaiwala R, Gopinath AK, Chockalingam R, Ayappa KG. Structure of the Bacterial Cell Envelope and Interactions with Antimicrobials: Insights from Molecular Dynamics Simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:7791-7811. [PMID: 38451026 DOI: 10.1021/acs.langmuir.3c03474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/08/2024]
Abstract
Bacteria have evolved over 3 billion years, shaping our intrinsic and symbiotic coexistence with these single-celled organisms. With rising populations of drug-resistant strains, the search for novel antimicrobials is an ongoing area of research. Advances in high-performance computing platforms have led to a variety of molecular dynamics simulation strategies to study the interactions of antimicrobial molecules with different compartments of the bacterial cell envelope of both Gram-positive and Gram-negative species. In this review, we begin with a detailed description of the structural aspects of the bacterial cell envelope. Simulations concerned with the transport and associated free energy of small molecules and ions through the outer membrane, peptidoglycan, inner membrane and outer membrane porins are discussed. Since surfactants are widely used as antimicrobials, a section is devoted to the interactions of surfactants with the cell wall and inner membranes. The review ends with a discussion on antimicrobial peptides and the insights gained from the molecular simulations on the free energy of translocation. Challenges involved in developing accurate molecular models and coarse-grained strategies that provide a trade-off between atomic details with a gain in sampling time are highlighted. The need for efficient sampling strategies to obtain accurate free energies of translocation is also discussed. Molecular dynamics simulations have evolved as a powerful tool that can potentially be used to design and develop novel antimicrobials and strategies to effectively treat bacterial infections.
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Affiliation(s)
- Pradyumn Sharma
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka, India, 560012
| | - Rakesh Vaiwala
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka, India, 560012
| | - Amar Krishna Gopinath
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka, India, 560012
| | - Rajalakshmi Chockalingam
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka, India, 560012
| | - K Ganapathy Ayappa
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka, India, 560012
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Wang G. The antimicrobial peptide database is 20 years old: Recent developments and future directions. Protein Sci 2023; 32:e4778. [PMID: 37695921 PMCID: PMC10535814 DOI: 10.1002/pro.4778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 09/05/2023] [Accepted: 09/07/2023] [Indexed: 09/13/2023]
Abstract
In 2023, the Antimicrobial Peptide Database (currently available at https://aps.unmc.edu) is 20-years-old. The timeline for the APD expansion in peptide entries, classification methods, search functions, post-translational modifications, binding targets, and mechanisms of action of antimicrobial peptides (AMPs) has been summarized in our previous Protein Science paper. This article highlights new database additions and findings. To facilitate antimicrobial development to combat drug-resistant pathogens, the APD has been re-annotating the data for antibacterial activity (active, inactive, and uncertain), toxicity (hemolytic and nonhemolytic AMPs), and salt tolerance (salt sensitive and insensitive). Comparison of the respective desired and undesired AMP groups produces new knowledge for peptide design. Our unification of AMPs from the six life kingdoms into "natural AMPs" enabled the first comparison with globular or transmembrane proteins. Due to the dominance of amphipathic helical and disulfide-linked peptides, cysteine, glycine, and lysine in natural AMPs are much more abundant than those in globular proteins. To include peptides predicted by machine learning, a new "predicted" group has been created. Remarkably, the averaged amino acid composition of predicted peptides is located between the lower bound of natural AMPs and the upper bound of synthetic peptides. Synthetic peptides in the current APD, with the highest cationic and hydrophobic amino acid percentages, are mostly designed with varying degrees of optimization. Hence, natural AMPs accumulated in the APD over 20 years have laid the foundation for machine learning prediction. We discuss future directions for peptide discovery. It is anticipated that the APD will continue to play a role in research and education.
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Affiliation(s)
- Guangshun Wang
- Department of Pathology and Microbiology, College of MedicineUniversity of Nebraska Medical CenterOmahaNebraskaUSA
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Leite ML, Duque HM, Rodrigues GR, da Cunha NB, Franco OL. The LL-37 domain: a clue to cathelicidin immunomodulatory response? Peptides 2023; 165:171011. [PMID: 37068711 DOI: 10.1016/j.peptides.2023.171011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 04/12/2023] [Accepted: 04/14/2023] [Indexed: 04/19/2023]
Abstract
Host defense peptides (HDPs) are naturally occurring polypeptide sequences that, in addition to being active against bacteria, fungi, viruses, and other parasites, may stimulate immunomodulatory responses. Cathelicidins, a family of HDPs, are produced by diverse animal species, such as mammals, fish, birds, amphibians, and reptiles, to protect them against pathogen infections. These peptides have variable C-terminal domains responsible for their antimicrobial and immunomodulatory activities and a highly conserved N-terminal pre-pro region homologous to cathelin. Although cathelicidins are the major components of innate immunity, the molecular basis by which they induce an immune response is still unclear. In this review, we will address the role of the LL-37 domain and its SK-24, IV-20, FK-13 and LL-37 fragments in the immunity response. Other cathelicidins also share structural and functional characteristics with the LL-37 domain, suggesting that these fragments may be responsible for interaction between these peptides and receptors in humans. Fragments of the LL-37 domain can give us clues about how homologous cathelicidins, in general, induce an immune response. AVAILABILITY OF DATA AND MATERIAL: No data was used for the research described in the article.
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Affiliation(s)
- Michel Lopes Leite
- Departamento de Biologia Molecular, Instituto de Ciências Biológicas, Universidade de Brasília, Campus Darcy Ribeiro, Brasília, Distrito Federal, Brazil
| | - Harry Morales Duque
- Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília, Brazil
| | - Gisele Regina Rodrigues
- Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília, Brazil
| | - Nicolau Brito da Cunha
- Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília, Brazil; Faculdade de Agronomia e Medicina Veterinária, Campus Darcy Ribeiro, Brasília, Brasil
| | - Octávio Luiz Franco
- Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília, Brazil; S-Inova Biotech, Programa de Pós-Graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande, Brazil.
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Deciphering Structure-Function Relationship Unveils Salt-Resistant Mode of Action of a Potent MRSA-Inhibiting Antimicrobial Peptide, RR14. J Bacteriol 2022; 204:e0031222. [PMID: 36377870 PMCID: PMC9765028 DOI: 10.1128/jb.00312-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Multidrug-resistant (MDR) bacteria lead to considerable morbidity and mortality, threatening public health worldwide. In particular, infections of methicillin-resistant Staphylococcus aureus (MRSA) in hospital and community settings are becoming a serious health problem. Antimicrobial peptides (AMPs) are considered novel therapeutic targets against MDR bacteria. However, salt sensitivity reduces the bactericidal potency of AMPs, posing a major obstacle for their development as antibiotics. Thus, the design and development of salt-insensitive peptides with potent antibacterial activity is imperative. Here, we employed biochemical and biophysical examinations coupled with molecular modeling to systematically investigate the structure-function relationship of a novel salt-insensitive AMP, RR14. The secondary structure of RR14 was characterized as an apparent α-helix, a structure that confers strong membrane-permeabilizing ability targeting bacterial-mimetic membranes. Additionally, the bioactive structure of RR14 was determined in complex with dodecylphosphocholine (DPC) micelles, where it possesses a central α-helical segment comprising residues R4 to K13 (R4-K13). RR14 was observed to orient itself into the DPC micelle with its N terminus and the α-helical segment (I5-R10) buried inside the micelles, which is essential for membrane permeabilization and bactericidal activity. Moreover, the specific and featured arrangement of positively charged residues of RR14 on its amphipathic helical conformation has great potential to render its strong salt resistance ability. Our study explored the structure-function relationship of RR14, explaining its possible mode of action against MRSA and other microbes. The insights obtained are of great applicability for the development of new antibacterial agents. IMPORTANCE Many antimicrobial peptides have been observed to become inactive in the presence of high salt concentrations. To further develop new and novel AMPs with potent bactericidal activity and salt insensitivity, understanding the structural basis for salt resistance is important. Here, we employed biochemical and biophysical examinations to systematically investigate the structure-function relationship of a novel salt-insensitive AMP, RR14. RR14 was observed to orient itself into DPC micelles with the N terminus and the α-helical segment (I5-R10) buried inside the micelles, which is essential for membrane permeabilization and bactericidal activity. Moreover, the specific and featured arrangement of cationic residues of RR14 on its amphipathic helical conformation renders its strong salt resistance ability. The insights obtained are of great applicability for developing new antibacterial agents.
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Lee SG, Kiattiburut W, Khongkha T, Schinkel SCB, Lunn Y, Decker AP, Mohammadi A, Vera-Cruz A, Misra A, Angel JB, Anderson DJ, Baker M, Kaul R, Wang G, Tanphaichitr N. 17BIPHE2, an engineered cathelicidin antimicrobial peptide with low susceptibility to proteases, is an effective spermicide and microbicide against Neisseria gonorrhoeae. Hum Reprod 2022; 37:2503-2517. [PMID: 36053257 PMCID: PMC9724780 DOI: 10.1093/humrep/deac188] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 08/03/2022] [Indexed: 11/14/2022] Open
Abstract
STUDY QUESTION Is 17BIPHE2, an engineered cathelicidin antimicrobial peptide with low susceptibility to proteases, a better spermicide in cervicovaginal fluid (CVF) than its parental peptides, LL-37 and GF-17? SUMMARY ANSWER At the same mass concentration, 17BIPHE2 exhibited the highest spermicidal activity on human sperm resuspended in CVF-containing medium. WHAT IS KNOWN ALREADY LL-37 and its truncated peptide GF-17 exert both spermicidal and microbicidal activities, although they are prone to proteolytic degradation in body fluids. STUDY DESIGN, SIZE, DURATION Spermicidal activities of 17BIPHE2 were evaluated in vitro in mouse and human sperm, both resuspended in medium, and then on human sperm incubated in CVF-containing medium; in the latter condition, the spermicidal activity and peptide stability in CVF of 17BIPHE2 were compared with that of LL-37 and GF-17. The in vivo contraceptive effects of 17BIPHE2 and the reversibility thereof were then assessed in mice. Finally, in vitro microbicidal effects of 17BIPHE2 on Neisseria gonorrhoeae were determined. PARTICIPANTS/MATERIALS, SETTING, METHODS Sperm motility and plasma membrane integrity were assessed by videomicroscopy and exclusion of Sytox Green, a membrane-impermeable fluorescent dye, respectively. Successful in vitro fertilization (IVF) was determined by the presence of two pronuclei in oocytes following their coincubation with capacitated untreated or 17BIPHE2-treated sperm. Sperm alone or with 17BIPHE2 were transcervically injected into female mice and successful in vivo fertilization was indicated by the formation of two-cell embryos 42-h postinjection, and by pregnancy through pup delivery 21-25 days afterwards. Peptide intactness was assessed by immunoblotting and HPLC. Reversibility of the contraceptive effects of 17BIPHE2 was evaluated by resumption of pregnancy of the female mice, pretranscervically injected with 17BIPHE2, following natural mating with fertile males. Minimum inhibitory/bactericidal concentrations of 17BIPHE2 on N. gonorrhoeae were obtained through microdilution broth assay. MAIN RESULTS AND THE ROLE OF CHANCE At the same mass concentration, 17BIPHE2 was a more effective spermicide than LL-37 or GF-17 on human sperm resuspended in CVF-containing medium, with the spermicidal concentration of 32.4 µM. This was mainly due to lower susceptibility of 17BIPHE2 to CVF proteases. Importantly, the reproductive tract of mouse females treated three times with 32.4 µM 17BIPHE2 remained normal and their fecundity resumed after stopping 17BIPHE2 treatment. LIMITATIONS, REASONS FOR CAUTION For ethical reasons, the inhibitory effects of 17BIPHE2 on fertilization and pregnancy cannot presently be performed in women. Also, while our study has proven the effectiveness of 17BIPHE2 as a spermicide for mouse and human sperm in vitro, dosage formulation (e.g. in hydrogel) of 17BIPHE2 still needs to be developed to allow 17BIPHE2 to remain in the vagina/uterine cavity with controlled release for its spermicidal action. WIDER IMPLICATIONS OF THE FINDINGS Since 17BIPHE2 also exerted bactericidal activity against N. gonorrhoeae at its spermicidal concentration, it is a promising candidate to be developed into a vaginal multipurpose prevention technology agent, thus empowering women against unplanned pregnancies and sexually transmitted infections. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the Canadian Institutes of Health Research (PJT 173268 to N.T.). There are no competing interests to declare. TRIAL REGISTRATION NUMBER N/A.
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Affiliation(s)
- Seung Gee Lee
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | | | - Thitiporn Khongkha
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | | | - Yvonne Lunn
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Aaron P Decker
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, Omaha, NE, USA
| | - Avid Mohammadi
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Ana Vera-Cruz
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Avika Misra
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Jonathan B Angel
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
- Division of Infectious Diseases, Department of Medicine, The Ottawa Hospital, Ottawa, ON, Canada
| | - Deborah J Anderson
- Department of Medicine, Boston University School of Medicine, Boston, MA, USA
| | - Mark Baker
- Department of Biological Science, University of Newcastle, Callaghan, NSW, Australia
| | - Rupert Kaul
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, Omaha, NE, USA
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Guangshun Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, Omaha, NE, USA
| | - Nongnuj Tanphaichitr
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Obstetrics/Gynecology, University of Ottawa, Ottawa, ON, Canada
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Rivera-Sanchez SP, Ocampo-Ibáñez ID, Liscano Y, Martínez N, Muñoz I, Manrique-Moreno M, Martinez-Martinez L, Oñate-Garzon J. Integrating In Vitro and In Silico Analysis of a Cationic Antimicrobial Peptide Interaction with Model Membranes of Colistin-Resistant Pseudomonas aeruginosa Strains. Pharmaceutics 2022; 14:pharmaceutics14061248. [PMID: 35745820 PMCID: PMC9230736 DOI: 10.3390/pharmaceutics14061248] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/03/2022] [Accepted: 06/08/2022] [Indexed: 02/04/2023] Open
Abstract
Bacterial antibiotic resistance is a serious global public health concern. Infections caused by colistin-resistant Pseudomonas aeruginosa (CRPa) strains represent a serious threat due to their considerable morbidity and mortality rates, since most of the current empirical antibiotic therapies are ineffective against these strains. Accordingly, cationic antimicrobial peptides (CAMPs) have emerged as promising alternatives to control resistant bacteria. In this study, the interaction of a CAMP derived from cecropin D-like (∆M2) with model membranes mimicking bacterial biomembranes of wild-type (WTPa) strains of P. aeruginosa and CRPa was evaluated through in vitro and in silico approaches. In vitro interaction was determined by infrared spectroscopy, whereas in silico molecular dynamics was performed to predict specific interactions between amino acids of ∆M2 and lipids of model membrane systems. Experimental analysis showed this peptide interacted with the lipids of bacterial-like model membranes of WTPa and CRPa. In both cases, an increase in the concentration of peptides induced an increase in the phase transition temperature of the lipid systems. On the other hand, the peptides in solution underwent a transition from a random to a helical secondary structure after interacting with the membranes mostly favored in the CRPa system. The α-helix structure percentage for ΔM2 interacting with WTPa and CRPa lipid systems was 6.4 and 33.2%, respectively. Finally, molecular dynamics showed ∆M2 to have the most affinities toward the phospholipids palmitoyl-oleyl-phosphatidylglycerol (POPG) and palmitoyl-oleoyl-phosphatidylethanolamine (POPE) that mimic membranes of WTPa and CRPa, respectively. This work provides clues for elucidating the membrane-associated mechanism of action of ∆M2 against colistin-susceptible and -resistant strains of Pseudomonas aeruginosa.
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Affiliation(s)
- Sandra Patricia Rivera-Sanchez
- Research Group of Microbiology, Industry and Environment, Faculty of Basic Sciences, Universidad Santiago of Cali, Cali 760035, Colombia; (I.D.O.-I.); (N.M.); (I.M.)
- Transnational Research Group on Infectious Diseases, PhD School of Biomedicine, University of Córdoba, 14071 Córdoba, Spain
- Correspondence: (S.P.R.-S.); (J.O.-G.)
| | - Iván Darío Ocampo-Ibáñez
- Research Group of Microbiology, Industry and Environment, Faculty of Basic Sciences, Universidad Santiago of Cali, Cali 760035, Colombia; (I.D.O.-I.); (N.M.); (I.M.)
| | - Yamil Liscano
- Research Group of Comprehensive Health (GISI), Department Faculty of Health, Universidad Santiago de Cali, Cali 760035, Colombia;
| | - Natalia Martínez
- Research Group of Microbiology, Industry and Environment, Faculty of Basic Sciences, Universidad Santiago of Cali, Cali 760035, Colombia; (I.D.O.-I.); (N.M.); (I.M.)
| | - Isamar Muñoz
- Research Group of Microbiology, Industry and Environment, Faculty of Basic Sciences, Universidad Santiago of Cali, Cali 760035, Colombia; (I.D.O.-I.); (N.M.); (I.M.)
| | - Marcela Manrique-Moreno
- Chemistry Institute, Faculty of Exact and Natural Sciences, University of Antioquia, Medellin 050010, Colombia;
| | - Luis Martinez-Martinez
- Microbiology Unit, Reina Sofía University Hospital, 14008 Córdoba, Spain;
- Maimonides Institute for Biomedical Research of Córdoba, 14008 Córdoba, Spain
- Department of Agricultural Chemistry, Soil Sciencies and Microbiology, University of Córdoba, 14071 Córdoba, Spain
| | - José Oñate-Garzon
- Research Group of Chemistry and Biotechnology, Faculty of Basic Sciences, Universidad Santiago of Cali, Cali 760035, Colombia
- Correspondence: (S.P.R.-S.); (J.O.-G.)
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Structure and Activity of a Selective Antibiofilm Peptide SK-24 Derived from the NMR Structure of Human Cathelicidin LL-37. Pharmaceuticals (Basel) 2021; 14:ph14121245. [PMID: 34959645 PMCID: PMC8703873 DOI: 10.3390/ph14121245] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 11/17/2021] [Accepted: 11/24/2021] [Indexed: 12/16/2022] Open
Abstract
The deployment of the innate immune system in humans is essential to protect us from infection. Human cathelicidin LL-37 is a linear host defense peptide with both antimicrobial and immune modulatory properties. Despite years of studies of numerous peptides, SK-24, corresponding to the long hydrophobic domain (residues 9–32) in the anionic lipid-bound NMR structure of LL-37, has not been investigated. This study reports the structure and activity of SK-24. Interestingly, SK-24 is entirely helical (~100%) in phosphate buffer (PBS), more than LL-37 (84%), GI-20 (75%), and GF-17 (33%), while RI-10 and 17BIPHE2 are essentially randomly coiled (helix%: 7–10%). These results imply an important role for the additional N-terminal amino acids (likely E16) of SK-24 in stabilizing the helical conformation in PBS. It is proposed herein that SK-24 contains the minimal sequence for effective oligomerization of LL-37. Superior to LL-37 and RI-10, SK-24 shows an antimicrobial activity spectrum comparable to the major antimicrobial peptides GF-17 and GI-20 by targeting bacterial membranes and forming a helical conformation. Like the engineered peptide 17BIPHE2, SK-24 has a stronger antibiofilm activity than LL-37, GI-20, and GF-17. Nevertheless, SK-24 is least hemolytic at 200 µM compared with LL-37 and its other peptides investigated herein. Combined, these results enabled us to appreciate the elegance of the long amphipathic helix SK-24 nature deploys within LL-37 for human antimicrobial defense. SK-24 may be a useful template of therapeutic potential.
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Zeth K, Sancho-Vaello E. Structural Plasticity of LL-37 Indicates Elaborate Functional Adaptation Mechanisms to Bacterial Target Structures. Int J Mol Sci 2021; 22:ijms22105200. [PMID: 34068993 PMCID: PMC8156758 DOI: 10.3390/ijms22105200] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/28/2021] [Accepted: 05/12/2021] [Indexed: 11/16/2022] Open
Abstract
The human cathelicidin LL-37 is a multifunctional peptide of the human innate immune system. Among the various functions of LL-37, its antimicrobial activity is important in controlling the microorganisms of the human body. The target molecules of LL-37 in bacteria include membrane lipids, lipopolysaccharides (LPS), lipoteichoic acid (LTA), proteins, DNA and RNA. In this mini-review, we summarize the entity of LL-37 structural data determined over the last 15 years and specifically discuss features implicated in the interactions with lipid-like molecules. For this purpose, we discuss partial and full-length structures of LL-37 determined in the presence of membrane-mimicking detergents. This constantly growing structural database is now composed of monomers, dimers, tetramers, and fiber-like structures. The diversity of these structures underlines an unexpected plasticity and highlights the conformational and oligomeric adaptability of LL-37 necessary to target different molecular scaffolds. The recent co-crystal structures of LL-37 in complex with detergents are particularly useful to understand how these molecules mimic lipids and LPS to induce oligomerization and fibrillation. Defined detergent binding sites provide deep insights into a new class of peptide scaffolds, widening our view on the fascinating world of the LL-37 structural factotum. Together, the new structures in their evolutionary context allow for the assignment of functionally conserved residues in oligomerization and target interactions. Conserved phenylalanine and arginine residues primarily mediate those interactions with lipids and LPS. The interactions with macromolecules such as proteins or DNA remain largely unexplored and open a field for future studies aimed at structures of LL-37 complexes. These complexes will then allow for the structure-based rational design of LL-37-derived peptides with improved antibiotic properties.
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Affiliation(s)
- Kornelius Zeth
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark
- Correspondence: (K.Z.); (E.S.-V.); Tel.: +45-604-666-29 (K.Z.)
| | - Enea Sancho-Vaello
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
- Correspondence: (K.Z.); (E.S.-V.); Tel.: +45-604-666-29 (K.Z.)
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Antibacterial Activity of a Cationic Antimicrobial Peptide against Multidrug-Resistant Gram-Negative Clinical Isolates and Their Potential Molecular Targets. Molecules 2020; 25:molecules25215035. [PMID: 33142969 PMCID: PMC7663601 DOI: 10.3390/molecules25215035] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/10/2020] [Accepted: 10/24/2020] [Indexed: 12/20/2022] Open
Abstract
Antimicrobial resistance reduces the efficacy of antibiotics. Infections caused by multidrug-resistant (MDR), Gram-negative bacterial strains, such as Klebsiella pneumoniae (MDRKp) and Pseudomonas aeruginosa (MDRPa), are a serious threat to global health. However, cationic antimicrobial peptides (CAMPs) are promising as an alternative therapeutic strategy against MDR strains. In this study, the inhibitory activity of a cationic peptide, derived from cecropin D-like (ΔM2), against MDRKp and MDRPa clinical isolates, and its interaction with membrane models and bacterial genomic DNA were evaluated. In vitro antibacterial activity was determined using the broth microdilution test, whereas interactions with lipids and DNA were studied by differential scanning calorimetry and electronic absorption, respectively. A strong bactericidal effect of ΔM2 against MDR strains, with minimal inhibitory concentration (MIC) and minimal bactericidal concentrations (MBC) between 4 and 16 μg/mL, was observed. The peptide had a pronounced effect on the thermotropic behavior of the 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dimyristoyl-sn-glycero-3-phosphorylglycerol (DMPG) membrane models that mimic bacterial membranes. Finally, the interaction between the peptide and genomic DNA (gDNA) showed a hyperchromic effect, which indicates that ΔM2 can denature bacterial DNA strands via the grooves.
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Biswas K, Ilyas H, Datta A, Bhunia A. NMR Assisted Antimicrobial Peptide Designing: Structure Based Modifications and Functional Correlation of a Designed Peptide VG16KRKP. Curr Med Chem 2020; 27:1387-1404. [PMID: 31232231 DOI: 10.2174/0929867326666190624090817] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 05/16/2019] [Accepted: 05/29/2019] [Indexed: 01/08/2023]
Abstract
Antimicrobial Peptides (AMPs), within their realm incorporate a diverse group of structurally and functionally varied peptides, playing crucial roles in innate immunity. Over the last few decades, the field of AMP has seen a huge upsurge, mainly owing to the generation of the so-called drug resistant 'superbugs' as well as limitations associated with the existing antimicrobial agents. Due to their resilient biological properties, AMPs can very well form the sustainable alternative for nextgeneration therapeutic agents. Certain drawbacks associated with existing AMPs are, however, issues of major concern, circumventing which are imperative. These limitations mainly include proteolytic cleavage and hence poor stability inside the biological systems, reduced activity due to inadequate interaction with the microbial membrane, and ineffectiveness because of inappropriate delivery among others. In this context, the application of naturally occurring AMPs as an efficient prototype for generating various synthetic and designed counterparts has evolved as a new avenue in peptide-based therapy. Such designing approaches help to overcome the drawbacks of the parent AMPs while retaining the inherent activity. In this review, we summarize some of the basic NMR structure based approaches and techniques which aid in improving the activity of AMPs, using the example of a 16-residue dengue virus fusion protein derived peptide, VG16KRKP. Using first principle based designing technique and high resolution NMR-based structure characterization we validate different types of modifications of VG16KRKP, highlighting key motifs, which optimize its activity. The approaches and designing techniques presented can support our peers in their drug development work.
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Affiliation(s)
- Karishma Biswas
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII(M), Kolkata 700054, India
| | - Humaira Ilyas
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII(M), Kolkata 700054, India
| | - Aritreyee Datta
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII(M), Kolkata 700054, India
| | - Anirban Bhunia
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII(M), Kolkata 700054, India
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Wu PS, Lai SJ, Fung KM, Tseng TS. Characterization of the structure–function relationship of a novel salt-resistant antimicrobial peptide, RR12. RSC Adv 2020; 10:23624-23631. [PMID: 35517355 PMCID: PMC9054785 DOI: 10.1039/d0ra04299d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 06/15/2020] [Indexed: 11/21/2022] Open
Abstract
Antimicrobial peptides (AMPs) are potential candidates in designing new anti-infective agents. However, many AMPs show poor bactericidal activities in physical salt and serum solutions. Here, we disclosed the structure–function relationships of a novel salt-resistant antimicrobial peptide, RR12, which could further explain its mode of action and show its applicability in developing new antibacterial agents. Antimicrobial peptides (AMPs) are potential candidates in designing new anti-infective agents.![]()
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Affiliation(s)
- Ping-Sheng Wu
- Division of Infectious Diseases
- Department of Pediatrics
- Taipei Tzu Chi Hospital
- Buddhist Tzu Chi Medical Foundation
- New Taipei
| | - Shu-Jung Lai
- Institute of Biological Chemistry
- Academia Sinica
- Taipei 115
- Taiwan
- Graduate Institute of Biomedical Sciences
| | - Kit-Man Fung
- Institute of Biological Chemistry
- Academia Sinica
- Taipei 115
- Taiwan
| | - Tien-Sheng Tseng
- Institute of Molecular Biology
- National Chung Hsing University
- Taichung
- Taiwan
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12
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Narayana JL, Mishra B, Lushnikova T, Golla RM, Wang G. Modulation of antimicrobial potency of human cathelicidin peptides against the ESKAPE pathogens and in vivo efficacy in a murine catheter-associated biofilm model. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2019; 1861:1592-1602. [PMID: 31319057 PMCID: PMC6689428 DOI: 10.1016/j.bbamem.2019.07.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 07/03/2019] [Accepted: 07/11/2019] [Indexed: 12/22/2022]
Abstract
Antimicrobial peptides are essential components of innate immune systems that protect hosts from infection. They are also useful candidates for developing a new generation of antibiotics to fight antibiotic-resistant pathogens. Human innate immune peptide LL-37 can inhibit biofilm formation, but suffers from high cost due to a long peptide length and rapid protease degradation. To improve the peptide, we previously identified the major active region and changed the peptide backbone structure. This study designed two families of new peptides by altering peptide side chains. Interestingly, these peptides displayed differential potency against various ESKAPE pathogens in vitro and substantially reduced hemolysis. Further potency test in vivo revealed that 17tF-W eliminated the burden of methicillin-resistant Staphylococcus aureus (MRSA) USA300 in both mouse-embedded catheters and their surrounding tissues. In addition, peptide treatment suppressed the level of chemokine TNFα, and boosted the levels of chemokines MCP-1, IL-17A and IL-10 in the surrounding tissues of the infected catheter embedded in mice. In conclusion, we have designed a set of new LL-37 peptides with varying antimicrobial activities, opening the door to potential topical treatment of infections involving different drug-resistant pathogens.
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Affiliation(s)
- Jayaram Lakshmaiah Narayana
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
| | - Biswajit Mishra
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
| | - Tamara Lushnikova
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
| | - Radha M Golla
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
| | - Guangshun Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA.
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13
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Varnava KG, Mohid SA, Calligari P, Stella L, Reynison J, Bhunia A, Sarojini V. Design, Synthesis, Antibacterial Potential, and Structural Characterization of N-Acylated Derivatives of the Human Autophagy 16 Polypeptide. Bioconjug Chem 2019; 30:1998-2010. [PMID: 31145591 DOI: 10.1021/acs.bioconjchem.9b00290] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A synthetic antimicrobial peptide library based on the human autophagy 16 polypeptide has been developed. Designed acetylated peptides bearing lipids of different chain lengths resulted in peptides with enhanced potency compared to the parent Atg16. A 21-residue fragment of Atg16 conjugated to 4-methylhexanoic acid (K30) emerged as the most potent antibacterial, with negligible hemolysis. Several studies, including microscopy, dye leakage, and ITC, were conducted to gain insight into the antibacterial mechanism of action of the peptide. Visual inspection using both SEM and TEM revealed the membranolytic effect of the peptide on bacterial cells. The selectivity of the peptide against bacterial cell membranes was also proven using dye leakage assays. ITC analysis revealed the exothermic nature of the binding interaction of the peptide to D8PG micelles. The three-dimensional solution NMR structure of K30 in complex with dioctanoylphosphatidylglycerol (D8PG) micelles revealed that the peptide adopts a helix-loop-helix structure in the presence of anionic membrane lipids mimicking bacterial membranes. Intermolecular NOEs between the peptide and lipid deciphered the location of the peptide in the bound state, which was subsequently supported by the paramagnetic relaxation enhancement (PRE) NMR experiment. Collectively, these results describe the structure-function relationship of the peptide in the bacterial membrane.
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Affiliation(s)
- Kyriakos Gabriel Varnava
- School of Chemical Sciences , The University of Auckland , Private Bag 92019 , Auckland , New Zealand
| | - Sk Abdul Mohid
- Department of Biophysics , Bose Institute , P-1/12 CIT Scheme VII (M) , Kolkata 700054 , India
| | - Paolo Calligari
- Department of Chemical Science and Technologies , University of Rome Tor Vergata , 00133 Rome , Italy
| | - Lorenzo Stella
- Department of Chemical Science and Technologies , University of Rome Tor Vergata , 00133 Rome , Italy
| | - Jóhannes Reynison
- School of Chemical Sciences , The University of Auckland , Private Bag 92019 , Auckland , New Zealand.,School of Pharmacy, Hornbeam Building , Keele University , Staffordshire ST5 5BG , United Kingdom
| | - Anirban Bhunia
- Department of Biophysics , Bose Institute , P-1/12 CIT Scheme VII (M) , Kolkata 700054 , India
| | - Vijayalekshmi Sarojini
- School of Chemical Sciences , The University of Auckland , Private Bag 92019 , Auckland , New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140 , New Zealand
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14
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Evaluation of the Antimicrobial Activity of Cationic Peptides Loaded in Surface-Modified Nanoliposomes against Foodborne Bacteria. Int J Mol Sci 2019; 20:ijms20030680. [PMID: 30764495 PMCID: PMC6386929 DOI: 10.3390/ijms20030680] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/31/2019] [Accepted: 02/02/2019] [Indexed: 01/03/2023] Open
Abstract
Bacteria are a common group of foodborne pathogens presenting public health issues with a large economic burden for the food industry. Our work focused on a solution to this problem by evaluating antibiotic activity against two bacteria (Listeria monocytogenes and Escherichia coli) of relevance in the field of foodstuffs. We used two approaches: (i) structural modification of the antimicrobial peptides and (ii) nano-vehiculisation of the modified peptides into polymer-coated liposomes. To achieve this, two antimicrobial peptides, herein named ‘peptide +2′ and ‘peptide +5′ were synthesised using the solid phase method. The physicochemical characterisation of the peptides was carried out using measurements of surface tension and dynamic light scattering. Additionally, nanoliposomes were elaborated by the ethanol injection method and coated with a cationic polymer (Eudragit E-100) through the layer-by-layer process. Liposome characterisation, in terms of size, polydispersity and zeta potential, was undertaken using dynamic light scattering. The results show that the degree of hydrophilic modification in the peptide leads to different characteristics of amphipathicity and subsequently to different physicochemical behaviour. On the other hand, antibacterial activity against both bacteria was slightly altered after modifying peptide sequence. Nonetheless, after the encapsulation of the peptides into polymer-coated nano-liposomes, the antibacterial activity increased approximately 2000-fold against that of L. monocytogenes.
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15
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Design of Antimicrobial Peptides: Progress Made with Human Cathelicidin LL-37. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1117:215-240. [PMID: 30980360 DOI: 10.1007/978-981-13-3588-4_12] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The incorporation of the innate immune system into humans is essential for survival and health due to the rapid replication of invading microbes and the delayed action of the adaptive immune system. Antimicrobial peptides are important components of human innate immunity. Over 100 such peptides have been identified in various human tissues. Human cathelicidin LL-37 is best studied, and there has been a growing interest in designing new peptides based on LL-37. This chapter describes the alternative processing of the human cathelicidin precursor, protease digestion, and lab cutting of LL-37. Both a synthetic peptide library and structure-based design are utilized to identify the active regions. Although challenging, the determination of the 3D structure of LL-37 enabled the identification of the core antimicrobial region. The minimal region of LL-37 can be function-dependent. We discuss the design and potential applications of LL-37 into antibacterial, antibiofilm, antiviral, antifungal, immune modulating, and anticancer peptides. LL-37 has been engineered into 17BIPHE2, a stable, selective, and potent antimicrobial, antibiofilm, and anticancer peptide. Both 17BIPHE2 and SAAP-148 can eliminate the ESKAPE pathogens and show topical in vivo antibiofilm efficacy. Also discussed are other application strategies, including peptide formulation, antimicrobial implants, and peptide-inducing factors such as vitamin D and sunlight. Finally, we summarize what we learned from peptide design based on human LL-37.
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16
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Jahangiri S, Jafari M, Arjomand M, Mehrnejad F. Molecular insights into the interactions of GF‐17 with the gram‐negative and gram‐positive bacterial lipid bilayers. J Cell Biochem 2018; 119:9205-9216. [DOI: 10.1002/jcb.27187] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 05/24/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Samira Jahangiri
- Department of Chemical Engineering South Tehran Branch, Islamic Azad University Tehran Iran
| | - Majid Jafari
- Computational Nanobiotechnology Laboratory, Department of Life Sciences Engineering Faculty of New Sciences and Technologies, University of Tehran Tehran Iran
| | - Mehdi Arjomand
- Department of Chemical Engineering South Tehran Branch, Islamic Azad University Tehran Iran
| | - Faramarz Mehrnejad
- Computational Nanobiotechnology Laboratory, Department of Life Sciences Engineering Faculty of New Sciences and Technologies, University of Tehran Tehran Iran
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17
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Oliva R, Chino M, Pane K, Pistorio V, De Santis A, Pizzo E, D'Errico G, Pavone V, Lombardi A, Del Vecchio P, Notomista E, Nastri F, Petraccone L. Exploring the role of unnatural amino acids in antimicrobial peptides. Sci Rep 2018; 8:8888. [PMID: 29892005 PMCID: PMC5995839 DOI: 10.1038/s41598-018-27231-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 05/23/2018] [Indexed: 12/14/2022] Open
Abstract
Cationic antimicrobial peptides (CAMPs) are a promising alternative to treat multidrug-resistant bacteria, which have developed resistance to all the commonly used antimicrobial, and therefore represent a serious threat to human health. One of the major drawbacks of CAMPs is their sensitivity to proteases, which drastically limits their half-life. Here we describe the design and synthesis of three nine-residue CAMPs, which showed high stability in serum and broad spectrum antimicrobial activity. As for all peptides a very low selectivity between bacterial and eukaryotic cells was observed, we performed a detailed biophysical characterization of the interaction of one of these peptides with liposomes mimicking bacterial and eukaryotic membranes. Our results show a surface binding on the DPPC/DPPG vesicles, coupled with lipid domain formation, and, above a threshold concentration, a deep insertion into the bilayer hydrophobic core. On the contrary, mainly surface binding of the peptide on the DPPC bilayer was observed. These observed differences in the peptide interaction with the two model membranes suggest a divergence in the mechanisms responsible for the antimicrobial activity and for the observed high toxicity toward mammalian cell lines. These results could represent an important contribution to unravel some open and unresolved issues in the development of synthetic CAMPs.
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Affiliation(s)
- Rosario Oliva
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Marco Chino
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Katia Pane
- Department of Biology, University of Naples "Federico II", Via Cintia, I-80126, Naples, Italy
| | - Valeria Pistorio
- Department of Molecular Medicine and Medical Biotechnologies, University of Naples "Federico II", Via Pansini, 5, I-80131, Naples, Italy
| | - Augusta De Santis
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Elio Pizzo
- Department of Biology, University of Naples "Federico II", Via Cintia, I-80126, Naples, Italy
| | - Gerardino D'Errico
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Vincenzo Pavone
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Angela Lombardi
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Pompea Del Vecchio
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Eugenio Notomista
- Department of Biology, University of Naples "Federico II", Via Cintia, I-80126, Naples, Italy
| | - Flavia Nastri
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy
| | - Luigi Petraccone
- Department of Chemical Sciences, University of Naples "Federico II", via Cintia, I-80126, Naples, Italy.
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18
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Almaaytah A, Qaoud MT, Abualhaijaa A, Al-Balas Q, Alzoubi KH. Hybridization and antibiotic synergism as a tool for reducing the cytotoxicity of antimicrobial peptides. Infect Drug Resist 2018; 11:835-847. [PMID: 29910626 PMCID: PMC5987794 DOI: 10.2147/idr.s166236] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Introduction As the development of new antimicrobial agents faces a historical decline, the issue of bacterial drug resistance has become a serious dilemma that threatens the human population worldwide. Antimicrobial peptides (AMPs) represent an attractive and a promising class of antimicrobial agents. Aim The hybridization of AMPs aimed at merging two individual active fragments of native peptides to generate a new AMP with altered physicochemical properties that translate into an enhanced safety profile. Materials and methods In this study, we have rationally designed a new hybrid peptide via combining two individual α-helical fragments of both BMAP-27 and OP-145. The resultant peptide, was evaluated for its antimicrobial and antibiofilm activity against a range of microbial strains. The resultant peptide was also evaluated for its toxicity against mammalian cells using hemolytic and anti proliferative assays. Results The antimicrobial activity of H4 revealed that the peptide is displaying a broad spectrum of activity against both Gram-positive and Gram-negative bacteria including standard and multidrug-resistant bacterial strains in the range of 2.5-25 μM. The new hybrid peptide displayed potent activity in eradicating biofilm-forming cells, and the reported minimum biofilm eradication concentrations were equal to the minimum inhibitory concentration values reported for planktonic cells. Additionally, H4 exhibited reduced toxicity profiles against eukaryotic cells. Combining H4 peptide with conventional antibiotics has led to a dramatic enhancement of the antimicrobial activity of both agents with synergistic or additive outcomes. Conclusion Overall, this study indicates the success of both the hybridization and synergism strategy in developing AMPs as potential antimicrobial therapeutics with reduced toxicity profiles that could be efficiently employed to eradicate resistant bacterial strains and enhance the selectivity and toxicity profiles of native AMPs.
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Affiliation(s)
- Ammar Almaaytah
- Department of Pharmaceutical Technology, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan
| | - Mohammed T Qaoud
- Department of Pharmaceutical Technology, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan
| | - Ahmad Abualhaijaa
- Department of Applied Biological Sciences, Faculty of Science and Arts, Jordan University of Science and Technology, Irbid, Jordan
| | - Qosay Al-Balas
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan
| | - Karem H Alzoubi
- Department Clinical Pharmacy, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan
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19
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In silico optimization of a guava antimicrobial peptide enables combinatorial exploration for peptide design. Nat Commun 2018; 9:1490. [PMID: 29662055 PMCID: PMC5902452 DOI: 10.1038/s41467-018-03746-3] [Citation(s) in RCA: 159] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Accepted: 03/02/2018] [Indexed: 12/29/2022] Open
Abstract
Plants are extensively used in traditional medicine, and several plant antimicrobial peptides have been described as potential alternatives to conventional antibiotics. However, after more than four decades of research no plant antimicrobial peptide is currently used for treating bacterial infections, due to their length, post-translational modifications or high dose requirement for a therapeutic effect . Here we report the design of antimicrobial peptides derived from a guava glycine-rich peptide using a genetic algorithm. This approach yields guavanin peptides, arginine-rich α-helical peptides that possess an unusual hydrophobic counterpart mainly composed of tyrosine residues. Guavanin 2 is characterized as a prototype peptide in terms of structure and activity. Nuclear magnetic resonance analysis indicates that the peptide adopts an α-helical structure in hydrophobic environments. Guavanin 2 is bactericidal at low concentrations, causing membrane disruption and triggering hyperpolarization. This computational approach for the exploration of natural products could be used to design effective peptide antibiotics. Antimicrobial peptides are considered promising alternatives to antibiotics. Here the authors developed a computational algorithm that starts with peptides naturally occurring in plants and optimizes this starting material to yield new variants which are highly distinct from the parent peptide.
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20
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Wang X, Mishra B, Lushnikova T, Narayana JL, Wang G. Amino Acid Composition Determines Peptide Activity Spectrum and Hot-Spot-Based Design of Merecidin. ACTA ACUST UNITED AC 2018; 2. [PMID: 30800727 DOI: 10.1002/adbi.201700259] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
There is a great interest in developing the only human cathelicidin into therapeutic molecules. The major antimicrobial region of human LL-37 corresponds to residues 17-32. The resultant peptide GF-17 shows a broad spectrum of antimicrobial activity against both Gram-positive and negative bacteria. By reducing the hydrophobic content, we previously succeeded in converting the broad-spectrum GF-17 to two narrow-spectrum peptides (GF-17d3 and KR-12) with activity against Gram-negative bacteria. This study demonstrates that substitution of multiple basic amino acids by hydrophobic alanines makes a broad-spectrum peptide 17BIPHE2 (designed based on GF-17d3) active against Staphylococcal pathogens but not other bacteria tested. Taken together, our results reveal distinct charge and hydrophobic requirements for peptides to kill Gram-positive or Gram-negative bacteria. This finding is in line with the bioinformatics analysis of the peptides in the Antimicrobial Peptide Database (http://aps.unmc.edu/AP). In addition, a hot spot arginine is identified and used to design merecidin with reduced toxicity to human cells. Merecidin protects wax moth larvae (Galleria mellonella) from the infection of methicillin-resistant S. aureus USA300. These new selective peptides constitute interesting candidates for future development.
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Affiliation(s)
- Xiuqing Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA.,Department of Surgery, General Hospital of Ningxia Medical University, Yinchuan 750004, China
| | - Biswajit Mishra
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
| | - Tamara Lushnikova
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
| | - Jayaram Lakshmaiah Narayana
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
| | - Guangshun Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE 68198-5900, USA
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21
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Almaaytah A, Qaoud MT, Khalil Mohammed G, Abualhaijaa A, Knappe D, Hoffmann R, Al-Balas Q. Antimicrobial and Antibiofilm Activity of UP-5, an Ultrashort Antimicrobial Peptide Designed Using Only Arginine and Biphenylalanine. Pharmaceuticals (Basel) 2018; 11:ph11010003. [PMID: 29301331 PMCID: PMC5874699 DOI: 10.3390/ph11010003] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/17/2017] [Accepted: 12/27/2017] [Indexed: 12/23/2022] Open
Abstract
The recent upsurge of multidrug resistant bacteria (MDRB) among global communities has become one of the most serious challenges facing health professionals and the human population worldwide. Cationic ultrashort antimicrobial peptides (USAMPs) are a promising group of molecules that meet the required criteria of novel antimicrobial drug development. UP-5, a novel penta-peptide, displayed significant antimicrobial activities against various standard and clinical isolates of MDRB. UP-5 displayed MICs values within the range of (10–15 μM) and (55–65 μM) against Gram-positive and Gram-negative bacteria, respectively. Furthermore, UP-5 displayed antibiofilm activity with minimum biofilm eradication concentration (MBEC) value as equal to twofold higher than MIC value. At the same inhibitory concentrations, UP-5 exhibited very low or negligible toxicity toward human erythrocytes and mammalian cells. Combining UP-5 with conventional antibiotics led to a synergistic or additive mode of action that resulted in the reduction of the MIC values for some of the antibiotics by 99.7% along a significant drop in MIC values of the peptide. The stability profile of UP-5 was evaluated in full mouse plasma and serum with results indicating a more stable pattern in plasma. The present study indicates that USAMPs are promising antimicrobial agents that can avoid the negative characteristics of conventional antimicrobial peptides. Additionally, USAMPs exhibit good to moderate activity against MDRB, negligible toxicity, and synergistic outcomes in combination with conventional antimicrobial agents.
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Affiliation(s)
- Ammar Almaaytah
- Department of Pharmaceutical Technology, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan.
| | - Mohammed T Qaoud
- Department of Pharmaceutical Technology, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan.
| | - Gubran Khalil Mohammed
- Department of Pharmaceutical Technology, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan.
| | - Ahmad Abualhaijaa
- Department of Applied Biological Sciences, Faculty of Science and Arts, Jordan University of Science and Technology, Irbid 22110 Jordan.
| | - Daniel Knappe
- Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy and Center for Biotechnology and Biomedicine, Universität Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany.
| | - Ralf Hoffmann
- Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy and Center for Biotechnology and Biomedicine, Universität Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany.
| | - Qosay Al-Balas
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan.
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22
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The increase in positively charged residues in cecropin D-like Galleria mellonella favors its interaction with membrane models that imitate bacterial membranes. Arch Biochem Biophys 2017; 629:54-62. [DOI: 10.1016/j.abb.2017.07.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 06/16/2017] [Accepted: 07/13/2017] [Indexed: 01/30/2023]
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23
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Zarena D, Mishra B, Lushnikova T, Wang F, Wang G. The π Configuration of the WWW Motif of a Short Trp-Rich Peptide Is Critical for Targeting Bacterial Membranes, Disrupting Preformed Biofilms, and Killing Methicillin-Resistant Staphylococcus aureus. Biochemistry 2017; 56:4039-4043. [PMID: 28731688 PMCID: PMC5603908 DOI: 10.1021/acs.biochem.7b00456] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tryptophan-rich peptides, being short and suitable for large-scale chemical synthesis, are attractive candidates for developing a new generation of antimicrobials to combat antibiotic-resistant bacteria (superbugs). Although there are numerous pictures of the membrane-bound structure of a single tryptophan (W), how multiple Trp amino acids assemble themselves and interact with bacterial membranes is poorly understood. This communication presents the three-dimensional structure of an eight-residue Trp-rich peptide (WWWLRKIW-NH2 with 50% W) determined by the improved two-dimensional nuclear magnetic resonance method, which includes the measurements of 13C and 15N chemical shifts at natural abundance. This peptide forms the shortest two-turn helix with a distinct amphipathic feature. A unique structural arrangement is identified for the Trp triplet, WWW, that forms a π configuration with W2 as the horizontal bar and W1/W3 forming the two legs. An arginine scan reveals that the WWW motif is essential for killing methicillin-resistant Staphylococcus aureus USA300 and disrupting preformed bacterial biofilms. This unique π configuration for the WWW motif is stabilized by aromatic-aromatic interactions as evidenced by ring current shifts as well as nuclear Overhauser effects. Because the WWW motif is maintained, a change of I7 to R led to a potent antimicrobial and antibiofilm peptide with 4-fold improvement in cell selectivity. Collectively, this study elucidated the structural basis of antibiofilm activity of the peptide, identified a better peptide candidate via structure-activity relationship studies, and laid the foundation for engineering future antibiotics based on the WWW motif.
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Affiliation(s)
- D. Zarena
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
- Department of Physics, JNTUA College of Engineering, Anantapur 515002, India
| | - Biswajit Mishra
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
| | - Tamara Lushnikova
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
| | - Fangyu Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
- Henan Key Laboratory for Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou 450002, China
| | - Guangshun Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
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24
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Wang X, Junior JCB, Mishra B, Lushnikova T, Epand RM, Wang G. Arginine-lysine positional swap of the LL-37 peptides reveals evolutional advantages of the native sequence and leads to bacterial probes. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2017; 1859:1350-1361. [PMID: 28450045 PMCID: PMC5516960 DOI: 10.1016/j.bbamem.2017.04.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Revised: 04/14/2017] [Accepted: 04/19/2017] [Indexed: 10/19/2022]
Abstract
Antimicrobial peptides are essential components of the innate immune system of multicellular organisms. Although cationic and hydrophobic amino acids are known determinants of these amphipathic molecules for bacterial killing, it is not clear how lysine-arginine (K-R) positional swaps influence peptide structure and activity. This study addresses this question by investigating two groups of peptides (GF-17 and 17BIPHE2) derived from human cathelicidin LL-37. K-R positional swap showed little effect on minimal inhibitory concentrations of the peptides. However, there are clear differences in bacterial killing kinetics. The membrane permeation patterns vary with peptide and bacterial types, but not changes in fluorescent dyes, salts or pH. In general, the original peptide is more efficient in bacterial killing, but less toxic to human cells, than the K-R swapped peptides, revealing the evolutionary significance of the native sequence for host defense. The characteristic membrane permeation patterns for different bacteria suggest a possible application of these K-R positional-swapped peptides as molecular probes for the type of bacteria. Such differences are related to bacterial membrane compositions: minimal for Gram-positive Staphylococcus aureus with essentially all anionic lipids (cardiolipin and phosphatidylglycerol), but evident for Gram-negative Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli with a mixture of phosphatidylethanolamine and phosphatidylglycerol. Biophysical characterization found similar structures and binding affinities for these peptides in vesicle systems mimicking E. coli and S. aureus. It seems that interfacial arginines of GF-17 are preferred over lysines in bacterial membrane permeation. Our study sheds new light on the design of cationic amphipathic peptides.
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Affiliation(s)
- Xiuqing Wang
- Department of Pathology and Microbiology, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA; Department of Surgery, General Hospital of Ningxia Medical University, Yinchuan 750004, China
| | - José Carlos Bozelli Junior
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, Ontario L8S 4K1, Canada
| | - Biswajit Mishra
- Department of Pathology and Microbiology, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
| | - Tamara Lushnikova
- Department of Pathology and Microbiology, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, Ontario L8S 4K1, Canada
| | - Guangshun Wang
- Department of Pathology and Microbiology, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA.
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Tseng TS, Tsai KC, Chen C. Characterizing the structure-function relationship reveals the mode of action of a novel antimicrobial peptide, P1, from jumper ant Myrmecia pilosula. MOLECULAR BIOSYSTEMS 2017; 13:1193-1201. [PMID: 28470277 DOI: 10.1039/c6mb00810k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Microbial infections of antibiotic-resistant strains cause serious diseases and have a significant impact on public health worldwide, so novel antimicrobial drugs are urgently needed. Insect venoms, a rich source of bioactive components containing antimicrobial peptides (AMPs), are attractive candidates for new therapeutic agents against microbes. Recently, a novel peptide, P1, identified from the venom of the Australian jumper ant Myrmecia pilosula, showed potent antimicrobial activities against both Gram-negative and Gram-positive bacteria, but its structure-function relationship is unknown. Here, we used biochemical and biophysical techniques coupled with computational simulations to explore the mode of action of P1 interaction with dodecylphosphocholine (DPC) micelles as a model membrane system. Our circular dichroism (CD) and NMR studies revealed an amphipathic α-helical structure for P1 upon interaction with DPC micelles. A paramagnetic relaxation enhancement approach revealed that P1 orients its α-helix segment (F6-G14) into DPC micelles. In addition, the α-helix segment could be essential for membrane permeabilization and antimicrobial activity. Moreover, the arginine residues R8, R11, and R15 significantly contribute to helix formation and membrane-binding affinity. The lysine residue K19 of the C-terminus functionally guides P1 to interact with DPC micelles in the early interaction stage. Our study provides insights into the mode of action of P1, which is valuable in modifying and developing potent AMPs as antibiotic drugs.
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Affiliation(s)
- Tien-Sheng Tseng
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Keng-Chang Tsai
- National Research Institute of Chinese Medicine, Ministry of Health and Welfare, Taipei 112, Taiwan and The Ph.D. Program for Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Chinpan Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
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Wang X, Wang G. Insights into Antimicrobial Peptides from Spiders and Scorpions. Protein Pept Lett 2017; 23:707-21. [PMID: 27165405 DOI: 10.2174/0929866523666160511151320] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 05/03/2016] [Accepted: 05/08/2016] [Indexed: 12/19/2022]
Abstract
The venoms of spiders and scorpions contain a variety of chemical compounds. Antimicrobial peptides (AMPs) from these organisms were first discovered in the 1990s. As of May 2015, there were 42 spider's and 63 scorpion's AMPs in the Antimicrobial Peptide Database (http://aps.unmc.edu/AP). These peptides have demonstrated broad or narrow-spectrum activities against bacteria, fungi, viruses, and parasites. In addition, they can be toxic to cancer cells, insects and erythrocytes. To provide insight into such an activity spectrum, this article discusses the discovery, classification, structure and activity relationships, bioinformatics analysis, and potential applications of spider and scorpion AMPs. Our analysis reveals that, in the case of linear peptides, spiders use both glycine-rich and helical peptide models for defense, whereas scorpions use two distinct helical peptide models with different amino acid compositions to exert the observed antimicrobial activities and hemolytic toxicity. Our structural bioinformatics study improves the knowledge in the field and can be used to design more selective peptides to combat tumors, parasites, and viruses.
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Affiliation(s)
| | - Guangshun Wang
- Department of Pathology and Microbiology, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA.
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Lee JTY, Wang G, Tam YT, Tam C. Membrane-Active Epithelial Keratin 6A Fragments (KAMPs) Are Unique Human Antimicrobial Peptides with a Non-αβ Structure. Front Microbiol 2016; 7:1799. [PMID: 27891122 PMCID: PMC5105358 DOI: 10.3389/fmicb.2016.01799] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Accepted: 10/26/2016] [Indexed: 11/23/2022] Open
Abstract
Antibiotic resistance is a pressing global health problem that threatens millions of lives each year. Natural antimicrobial peptides and their synthetic derivatives, including peptoids and peptidomimetics, are promising candidates as novel antibiotics. Recently, the C-terminal glycine-rich fragments of human epithelial keratin 6A were found to have bactericidal and cytoprotective activities. Here, we used an improved 2-dimensional NMR method coupled with a new protocol for structural refinement by low temperature simulated annealing to characterize the solution structure of these kerain-derived antimicrobial peptides (KAMPs). Two specific KAMPs in complex with membrane mimicking sodium dodecyl sulfate (SDS) micelles displayed amphipathic conformations with only local bends and turns, and a central 10-residue glycine-rich hydrophobic strip that is central to bactericidal activity. To our knowledge, this is the first report of non-αβ structure for human antimicrobial peptides. Direct observation of Staphylococcus aureus and Pseudomonas aeruginosa by scanning and transmission electron microscopy showed that KAMPs deformed bacterial cell envelopes and induced pore formation. Notably, in competitive binding experiments, KAMPs demonstrated binding affinities to LPS and LTA that did not correlate with their bactericidal activities, suggesting peptide-LPS and peptide-LTA interactions are less important in their mechanisms of action. Moreover, immunoprecipitation of KAMPs-bacterial factor complexes indicated that membrane surface lipoprotein SlyB and intracellular machineries NQR sodium pump and ribosomes are potential molecular targets for the peptides. Results of this study improve our understanding of the bactericidal function of epithelial cytokeratin fragments, and highlight an unexplored class of human antimicrobial peptides, which may serve as non-αβ peptide scaffolds for the design of novel peptide-based antibiotics.
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Affiliation(s)
- Judy T Y Lee
- Department of Ophthalmic Research, Cole Eye Institute and Lerner Research Institute, Cleveland Clinic Cleveland, OH, USA
| | - Guangshun Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center Omaha, NE, USA
| | - Yu Tong Tam
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison Madison, WI, USA
| | - Connie Tam
- Department of Ophthalmic Research, Cole Eye Institute and Lerner Research Institute, Cleveland ClinicCleveland, OH, USA; Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve UniversityCleveland, OH, USA
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Usachev KS, Efimov SV, Kolosova OA, Klochkova EA, Aganov AV, Klochkov VV. Antimicrobial peptide protegrin-3 adopt an antiparallel dimer in the presence of DPC micelles: a high-resolution NMR study. JOURNAL OF BIOMOLECULAR NMR 2015; 62:71-79. [PMID: 25786621 DOI: 10.1007/s10858-015-9920-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 03/14/2015] [Indexed: 06/04/2023]
Abstract
A tendency to dimerize in the presence of lipids was found for the protegrin. The dimer formation by the protegrin-1 (PG-1) is the first step for further oligomeric membrane pore formation. Generally there are two distinct model of PG-1 dimerization in either a parallel or antiparallel β-sheet. But despite the wealth of data available today, protegrin dimer structure and pore formation is still not completely understood. In order to investigate a more detailed dimerization process of PG-1 and if it will be the same for another type of protegrins, in this work we used a high-resolution NMR spectroscopy for structure determination of protegrin-3 (RGGGL-CYCRR-RFCVC-VGR) in the presence of perdeuterated DPC micelles and demonstrate that PG-3 forms an antiparallel NCCN dimer with a possible association of these dimers. This structural study complements previously published solution, solid state and computational studies of PG-1 in various environments and validate the potential of mean force simulations of PG-1 dimers and association of dimers to form octameric or decameric β-barrels.
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Affiliation(s)
- K S Usachev
- NMR Laboratory, Institute of Physics, Kazan Federal University, Kremlevskaya, 18, Kazan, 420008, Russian Federation,
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Afonin S, Glaser RW, Sachse C, Salgado J, Wadhwani P, Ulrich AS. (19)F NMR screening of unrelated antimicrobial peptides shows that membrane interactions are largely governed by lipids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2260-8. [PMID: 24699372 DOI: 10.1016/j.bbamem.2014.03.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 03/23/2014] [Accepted: 03/24/2014] [Indexed: 02/07/2023]
Abstract
Many amphiphilic antimicrobial peptides permeabilize bacterial membranes via successive steps of binding, re-alignment and/or oligomerization. Here, we have systematically compared the lipid interactions of two structurally unrelated peptides: the cyclic β-pleated gramicidin S (GS), and the α-helical PGLa. (19)F NMR was used to screen their molecular alignment in various model membranes over a wide range of temperatures. Both peptides were found to respond to the phase state and composition of these different samples in a similar way. In phosphatidylcholines, both peptides first bind to the bilayer surface. Above a certain threshold concentration they can re-align and immerse more deeply into the hydrophobic core, which presumably involves oligomerization. Re-alignment is most favorable around the lipid chain melting temperature, and also promoted by decreasing bilayer thickness. The presence of anionic lipids has no influence in fluid membranes, but in the gel phase the alignment states are more complex. Unsaturated acyl chains and other lipids with intrinsic negative curvature prevent re-alignment, hence GS and PGLa do not insert into mixtures resembling bacterial membranes, nor into bacterial lipid extracts. Cholesterol, which is present in high concentrations in animal membranes, even leads to an expulsion of the peptides from the bilayer and prevents their binding altogether. However, a very low cholesterol content of 10% was found to promote binding and re-alignment of both peptides. Overall, these findings show that the ability of amphiphilic peptides to re-align and immerse into a membrane is determined by the physico-chemical properties of the lipids, such as spontaneous curvature. This idea is reinforced by the remarkably similar behavior observed here for two structurally unrelated molecules (with different conformation, size, shape, charge), which further suggests that their activity at the membrane level is largely governed by the properties of the constituent lipids, while the selectivity towards different cell types is additionally ruled by electrostatic attraction between peptide and cell surface. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.
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Affiliation(s)
- Sergii Afonin
- Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2), POB 3640, 76021 Karlsruhe, Germany
| | - Ralf W Glaser
- Institute of Biochemistry and Biophysics, Friedrich-Schiller-Universität Jena, Hans-Knöll-Str. 2, 07745 Jena, Germany
| | - Carsten Sachse
- EMBL - European Molecular Biology Laboratory, Structural and Computational Biology, Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Jesús Salgado
- Institute of Molecular Science (ICMol), University of Valencia, C/Catedrático José Beltrán, 2, 46980 Paterna, Valencia, Spain
| | - Parvesh Wadhwani
- Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2), POB 3640, 76021 Karlsruhe, Germany
| | - Anne S Ulrich
- Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2), POB 3640, 76021 Karlsruhe, Germany; Karlsruhe Institute of Technology (KIT), Institute of Organic Chemistry, Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany.
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30
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High-quality 3D structures shine light on antibacterial, anti-biofilm and antiviral activities of human cathelicidin LL-37 and its fragments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2160-72. [PMID: 24463069 DOI: 10.1016/j.bbamem.2014.01.016] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/26/2013] [Accepted: 01/10/2014] [Indexed: 01/07/2023]
Abstract
Host defense antimicrobial peptides are key components of human innate immunity that plays an indispensible role in human health. While there are multiple copies of cathelicidin genes in horses, cattle, pigs, and sheep, only one cathelicidin gene is found in humans. Interestingly, this single cathelicidin gene can be processed into different forms of antimicrobial peptides. LL-37, the most commonly studied form, is not only antimicrobial but also possesses other functional roles such as chemotaxis, apoptosis, wound healing, immune modulation, and cancer metastasis. This article reviews recent advances made in structural and biophysical studies of human LL-37 and its fragments, which serve as a basis to understand their antibacterial, anti-biofilm and antiviral activities. High-quality structures were made possible by using improved 2D NMR methods for peptide fragments and 3D NMR spectroscopy for intact LL-37. The two hydrophobic domains in the long amphipathic helix (residues 2-31) of LL-37 separated by a hydrophilic residue serine 9 explain its cooperative binding to bacterial lipopolysaccharides (LPS). Both aromatic rings (F5, F6, F17, and F27) and interfacial basic amino acids of LL-37 directly interact with anionic phosphatidylglycerols (PG). Although the peptide sequences reported in the literature vary slightly, there is a consensus that the central helix of LL-37 is essential for disrupting superbugs (e.g., MRSA), bacterial biofilms, and viruses such as human immunodeficiency virus 1 (HIV-1) and respiratory syncytial virus (RSV). In the central helix, the central arginine R23 is of particular importance in binding to bacterial membranes or DNA. Mapping the functional roles of the cationic amino acids of the major antimicrobial region of LL-37 provides a basis for designing antimicrobial peptides with desired properties. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.
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Database-Guided Discovery of Potent Peptides to Combat HIV-1 or Superbugs. Pharmaceuticals (Basel) 2013; 6:728-58. [PMID: 24276259 PMCID: PMC3816732 DOI: 10.3390/ph6060728] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 05/02/2013] [Accepted: 05/13/2013] [Indexed: 11/17/2022] Open
Abstract
Antimicrobial peptides (AMPs), small host defense proteins, are indispensable for the protection of multicellular organisms such as plants and animals from infection. The number of AMPs discovered per year increased steadily since the 1980s. Over 2,000 natural AMPs from bacteria, protozoa, fungi, plants, and animals have been registered into the antimicrobial peptide database (APD). The majority of these AMPs (>86%) possess 11–50 amino acids with a net charge from 0 to +7 and hydrophobic percentages between 31–70%. This article summarizes peptide discovery on the basis of the APD. The major methods are the linguistic model, database screening, de novo design, and template-based design. Using these methods, we identified various potent peptides against human immunodeficiency virus type 1 (HIV-1) or methicillin-resistant Staphylococcus aureus (MRSA). While the stepwise designed anti-HIV peptide is disulfide-linked and rich in arginines, the ab initio designed anti-MRSA peptide is linear and rich in leucines. Thus, there are different requirements for antiviral and antibacterial peptides, which could kill pathogens via different molecular targets. The biased amino acid composition in the database-designed peptides, or natural peptides such as θ-defensins, requires the use of the improved two-dimensional NMR method for structural determination to avoid the publication of misleading structure and dynamics. In the case of human cathelicidin LL-37, structural determination requires 3D NMR techniques. The high-quality structure of LL-37 provides a solid basis for understanding its interactions with membranes of bacteria and other pathogens. In conclusion, the APD database is a comprehensive platform for storing, classifying, searching, predicting, and designing potent peptides against pathogenic bacteria, viruses, fungi, parasites, and cancer cells.
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Dannehl C, Gutsmann T, Brezesinski G. Surface activity and structures of two fragments of the human antimicrobial LL-37. Colloids Surf B Biointerfaces 2013; 109:129-35. [PMID: 23624281 DOI: 10.1016/j.colsurfb.2013.03.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 03/22/2013] [Accepted: 03/25/2013] [Indexed: 10/27/2022]
Abstract
Two fragments of the antimicrobial peptide LL-37 (LL-32 and LL-20) have been characterized in adsorption layers at the air/buffer interface by infrared reflection absorption spectroscopy (IRRAS) and X-ray reflectivity (XR) measurements. As shown in previous work, LL-32 exhibits an increased antimicrobial activity compared to LL-37, while LL-20 is almost not active. It is shown in this work that the peptides differ drastically in their surface activity (equilibrium adsorption pressure) and their secondary structure, when they are adsorbed to the air/buffer interface. As concluded from the CD spectra, both peptides are unstructured in bulk. That means that the adsorption of the peptides to the air/buffer interface is connected to a secondary structure change. While LL-32 transforms into an α-helix lying flat at the buffer surface, with a helix diameter of 17Å, LL-20 adopts a partly unstructured conformation. The dichroic ratio of LL-20 is reduced and the electron density profile shows the formation of a second layer. The ability of LL-32 to form a complete α-helical structure at the interface is in good agreement with its higher antimicrobial activity.
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Affiliation(s)
- Claudia Dannehl
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
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Mishra B, Epand RF, Epand RM, Wang G. Structural location determines functional roles of the basic amino acids of KR-12, the smallest antimicrobial peptide from human cathelicidin LL-37. RSC Adv 2013. [PMID: 24307932 DOI: 10.1039/c3ra42599a] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cationic antimicrobial peptides are recognized templates for developing a new generation of antimicrobials to combat superbugs. Human cathelicidin LL-37 is an essential host defense molecule in human innate immunity. Previously, we identified KR-12 as the smallest antibacterial peptide of LL-37. KR-12 has a narrow activity spectrum since it is active against Gram-negative Escherichia coli but not Gram-positive Staphylococcus aureus. The functional roles of the basic amino acids of KR-12, however, have not yet been elucidated. An alanine scan of cationic amino acids of KR-12 provided evidence for their distinct roles in the activities of the peptides. Bacterial killing and membrane permeation experiments indicate that the R23A and K25A mutants, as well as the lysine-to-arginine mutant, were more potent than KR-12. Another three cationic residues (K18, R19, and R29) of KR-12, which are located in the hydrophilic face of the amphiphathic helix, appeared to be more important in clustering anionic lipids or hemolysis than R23 and K25 in the interfacial region. While the loss of interfacial R23 or K25 reduced peptide helicity, underscoring its important role in membrane binding, the overall increase in peptide activity of KR-12 could be ascribed to the increased peptide hydrophobicity that outweighed the role of basic charge in this case. In contrast, the mutations of interfacial R23 or K25 reduced peptide bactericidal activity of GF-17, an overlapping, more hydrophobic and potent peptide also derived from LL-37. Thus, the hydrophobic context of the peptide determines whether an alanine substitution of an interfacial basic residue increases or decreases membrane permeation and peptide activity.
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Affiliation(s)
- Biswajit Mishra
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
| | - Raquel F Epand
- Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre, Hamilton, Ontario, L8S 4K1, Canada
| | - Richard M Epand
- Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre, Hamilton, Ontario, L8S 4K1, Canada
| | - Guangshun Wang
- Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA
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Decoding the functional roles of cationic side chains of the major antimicrobial region of human cathelicidin LL-37. Antimicrob Agents Chemother 2011; 56:845-56. [PMID: 22083479 DOI: 10.1128/aac.05637-11] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human cathelicidin LL-37 is a critical cationic antimicrobial peptide for host defense against infection, immune modulation, and wound healing. This article elucidates the functional roles of the cationic side chains of the major antimicrobial region of LL-37, corresponding to residues 17 to 32 (designated GF-17). Antimicrobial assays, killing kinetics studies, and vesicle leakage experiments all indicate that a conversion of lysines to arginines affected the ability of the peptide to kill the Gram-positive Staphylococcus aureus strain USA300. Alanine scanning experiments show that S. aureus is less sensitive than Escherichia coli to a single cationic residue mutation of GF-17. Among the five cationic residues, R23 appears to be somewhat important in killing S. aureus. However, R23 and K25 of GF-17 are of prime importance in killing the Gram-negative organism E. coli. In particular, R23 is essential for (i) rapid recognition, (ii) permeation of the E. coli outer membrane, (iii) clustering of anionic lipids in a membrane system mimicking the E. coli inner membrane, and (iv) membrane disruption. Bacterial aggregation (i.e., rapid recognition via charge neutralization) is the first step of the peptide action. Structurally, R23 is located in the interface (i.e., the first action layer), a situation ideal for the interactions listed above. In contrast, residues K18, R19, and R29 are on the hydrophilic surface of the amphipathic helix and play only a secondary role. Mapping of the functional spectrum of cationic residues of GF-17 provides a solid basis for engineering bacterium-specific antimicrobials using this highly potent template.
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Saravanan R, Bhattacharjya S. Oligomeric structure of a cathelicidin antimicrobial peptide in dodecylphosphocholine micelle determined by NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:369-81. [PMID: 20933496 DOI: 10.1016/j.bbamem.2010.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Revised: 09/24/2010] [Accepted: 10/04/2010] [Indexed: 01/05/2023]
Abstract
The broad spectrum of antibacterial activities of host defense cationic antimicrobial peptides (AMPs) arises from their ability to perturb membrane integrity of the microbes. The mechanisms are often thought to require assembly of AMPs on the membrane surface to form pores. However, three dimensional structures in the oligomeric form of AMPs in the context of lipid membranes are largely limited. Here, we demonstrate that a 22-residue antimicrobial peptide, termed VK22, derived from fowlicidin-1, a cathelicidin family of AMP from chicken oligomerizes into a predominantly tetrameric state in zwitterionic dodecylphosphocholine (DPC) micelles. An ensemble of NMR structures of VK22 determined in 200mM perdeuterated DPC, from 755 NOE constrains including 19 inter-helical NOEs, had revealed an assembly of four helices arranged in anti-parallel fashion. Hydrogen bonds, C(α)H-O=C types, and van der Waals interactions among the helical sub-units appear to be involved in the stabilization of the quaternary structures. The central region of the barrel shaped tetrameric bundle is non-polar with clusters of aromatic residues, whereas all the cationic residues are positioned at the termini. Paramagnetic spin labeled NMR experiments indicated that the tetrameric structure is embedded into micelles such that the non-polar region located inside the lipid acyl chains. Structure and micelle localization of a monomeric version, obtained from substitution of two Tyr residues with Ala, of the peptide is also compared. The mutated peptide VK22AA has been found be localized at the surface of the micelles. The tetrameric structure of VK22 delineates a small water pore that can be larger in the higher order oligomers. As these results provide structural insights, at atomic resolution, into the oligomeric states of a helical AMP in lipid environment, the structural details may be further utilized for the design of novel self-assembled membrane protein mimics.
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Affiliation(s)
- Rathi Saravanan
- School of Biological Sciences, Division of Structural and Computational Biology, Nanyang Technological University, Singapore 637551, Singapore
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36
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Wu WKK, Wang G, Coffelt SB, Betancourt AM, Lee CW, Fan D, Wu K, Yu J, Sung JJY, Cho CH. Emerging roles of the host defense peptide LL-37 in human cancer and its potential therapeutic applications. Int J Cancer 2010; 127:1741-7. [PMID: 20521250 DOI: 10.1002/ijc.25489] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Human cathelicidin LL-37, a host defense peptide derived from leukocytes and epithelial cells, plays a crucial role in innate and adaptive immunity. Not only does LL-37 eliminate pathogenic microbes directly but also modulates host immune responses. Emerging evidence from tumor biology studies indicates that LL-37 plays a prominent and complex role in carcinogenesis. Although overexpression of LL-37 has been implicated in the development or progression of many human malignancies, including breast, ovarian and lung cancers, LL-37 suppresses tumorigenesis in gastric cancer. These data are beginning to unveil the intricate and contradictory functions of LL-37. The reasons for the tissue-specific function of LL-37 in carcinogenesis remain to be elucidated. Here, we review the relationship between LL-37, its fragments and cancer progression as well as discuss the potential therapeutic implications of targeting this peptide.
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Affiliation(s)
- William K K Wu
- Institute of Digestive Diseases, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
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Saravanan R, Bhunia A, Bhattacharjya S. Micelle-bound structures and dynamics of the hinge deleted analog of melittin and its diastereomer: Implications in cell selective lysis by d-amino acid containing antimicrobial peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:128-39. [DOI: 10.1016/j.bbamem.2009.07.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 06/04/2009] [Accepted: 07/17/2009] [Indexed: 10/20/2022]
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Abstract
LL-37 is a human host defence peptide that has a wide range of biological functions, including antimicrobial and immunomodulatory properties. This review summarises how molecular structure influences the balance between the immunomodulatory and antimicrobial functions of LL-37.
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Affiliation(s)
- Matthew F Burton
- Centre for Bioactive Chemistry, Department of Chemistry, University of Durham, Science Laboratory, South Road, Durham, DH1 3LE, UK.
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39
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Structure, dynamics and mapping of membrane-binding residues of micelle-bound antimicrobial peptides by natural abundance (13)C NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:114-21. [PMID: 19682427 DOI: 10.1016/j.bbamem.2009.07.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 06/08/2009] [Accepted: 07/30/2009] [Indexed: 12/23/2022]
Abstract
Worldwide bacterial resistance to traditional antibiotics has drawn much research attention to naturally occurring antimicrobial peptides (AMPs) owing to their potential as alternative antimicrobials. Structural studies of AMPs are essential for an in-depth understanding of their activity, mechanism of action, and in guiding peptide design. Two-dimensional solution proton NMR spectroscopy has been the major tool. In this article, we describe the applications of natural abundance (13)C NMR spectroscopy that provides complementary information to 2D (1)H NMR. The correlation of (13)Calpha secondary shifts with both 3D structure and heteronuclear (15)N NOE values indicates that natural abundance carbon chemical shifts are useful probes for backbone structure and dynamics of membrane peptides. Using human LL-37-derived peptides (GF-17, KR-12, and RI-10), as well as amphibian antimicrobial and anticancer peptide aurein 1.2 and its analog LLAA, as models, we show that the cross peak intensity plots of 2D (1)H-(13)Calpha HSQC spectra versus residue number present a wave-like pattern (HSQC wave) where key hydrophobic residues of micelle-bound peptides are located in the troughs with weaker intensities, probably due to fast exchange between the free and bound forms. In all the cases, the identification of aromatic phenylalanines as a key membrane-binding residue is consistent with previous intermolecular Phe-lipid NOE observations. Furthermore, mutation of one of the key hydrophobic residues of KR-12 to Ala significantly reduced the antibacterial activity of the peptide mutants. These results illustrate that natural abundance heteronuclear-correlated NMR spectroscopy can be utilized to probe backbone structure and dynamics, and perhaps to map key membrane-binding residues of peptides in complex with micelles. (1)H-(13)Calpha HSQC wave, along with other NMR waves such as dipolar wave and chemical shift wave, offers novel insights into peptide-membrane interactions from different angles.
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Lipid segregation explains selective toxicity of a series of fragments derived from the human cathelicidin LL-37. Antimicrob Agents Chemother 2009; 53:3705-14. [PMID: 19581460 DOI: 10.1128/aac.00321-09] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The only human cathelicidin, the 37-residue peptide LL-37, exhibits antimicrobial activity against both gram-positive and gram-negative bacteria. We studied the ability of several fragments of LL-37, exhibiting different antimicrobial activities, to interact with membranes whose compositions mimic the cytoplasmic membranes of gram-positive or of gram-negative bacteria. These fragments are as follows: KR-12, the smallest active segment of LL-37, with the sequence KRIVQRIKDFLR, which exhibits antimicrobial activity only against gram-negative bacteria; a slightly smaller peptide, RI-10, missing the two cationic residues at the N and C termini of KR-12, which has been shown not to have any antimicrobial activity; a longer peptide, GF-17, which shows antimicrobial activity against gram-positive as well as gram-negative bacteria; and GF-17D3, with 3 D-amino-acid residues, which is also selective only for gram-negative bacteria. Those fragments with the capacity to cluster anionic lipids away from zwitterionic lipids in a membrane exhibit selective toxicity toward bacteria containing zwitterionic as well as anionic lipids in their cytoplasmic membranes but not toward bacteria with only anionic lipids. This finding allows for the prediction of the bacterial-species selectivity of certain agents and paves the way for designing new antimicrobials targeted specifically toward gram-negative bacteria.
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41
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Wang G. Structures of human host defense cathelicidin LL-37 and its smallest antimicrobial peptide KR-12 in lipid micelles. J Biol Chem 2008; 283:32637-43. [PMID: 18818205 DOI: 10.1074/jbc.m805533200] [Citation(s) in RCA: 325] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As a key component of the innate immunity system, human cathelicidin LL-37 plays an essential role in protecting humans against infectious diseases. To elucidate the structural basis for its targeting bacterial membrane, we have determined the high quality structure of (13)C,(15)N-labeled LL-37 by three-dimensional triple-resonance NMR spectroscopy, because two-dimensional (1)H NMR did not provide sufficient spectral resolution. The structure of LL-37 in SDS micelles is composed of a curved amphipathic helix-bend-helix motif spanning residues 2-31 followed by a disordered C-terminal tail. The helical bend is located between residues Gly-14 and Glu-16. Similar chemical shifts and (15)N nuclear Overhauser effect (NOE) patterns of the peptide in complex with dioctanoylphosphatidylglycerol (D8PG) micelles indicate a similar structure. The aromatic rings of Phe-5, Phe-6, Phe-17, and Phe-27 of LL-37, as well as arginines, showed intermolecular NOE cross-peaks with D8PG, providing direct evidence for the association of the entire amphipathic helix with anionic lipid micelles. The structure of LL-37 serves as a model for understanding the structure and function relationship of homologous primate cathelicidins. Using synthetic peptides, we also identified the smallest antibacterial peptide KR-12 corresponding to residues 18-29 of LL-37. Importantly, KR-12 displayed a selective toxic effect on bacteria but not human cells. NMR structural analysis revealed a short three-turn amphipathic helix rich in positively charged side chains, allowing for effective competition for anionic phosphatidylglycerols in bacterial membranes. KR-12 may be a useful peptide template for developing novel antimicrobial agents of therapeutic use.
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Affiliation(s)
- Guangshun Wang
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
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