1
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Karami Y, Murail S, Giribaldi J, Lefranc B, Defontaine F, Lesouhaitier O, Leprince J, de Vries S, Tufféry P. Exploring a Structural Data Mining Approach to Design Linkers for Head-to-Tail Peptide Cyclization. J Chem Inf Model 2023; 63:6436-6450. [PMID: 37827517 PMCID: PMC10599322 DOI: 10.1021/acs.jcim.3c00865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Indexed: 10/14/2023]
Abstract
Peptides have recently regained interest as therapeutic candidates, but their development remains confronted with several limitations including low bioavailability. Backbone head-to-tail cyclization, i.e., setting a covalent peptide bond linking the last amino acid with the first one, is one effective strategy of peptide-based drug design to stabilize the conformation of bioactive peptides while preserving peptide properties in terms of low toxicity, binding affinity, target selectivity, and preventing enzymatic degradation. Starting from an active peptide, it usually requires the design of a linker of a few amino acids to make it possible to cyclize the peptide, possibly preserving the conformation of the initial peptide and not affecting its activity. However, very little is known about the sequence-structure relationship requirements of designing linkers for peptide cyclization in a rational manner. Recently, we have shown that large-scale data-mining of available protein structures can lead to the precise identification of protein loop conformations, even from remote structural classes. Here, we transpose this approach to linkers, allowing head-to-tail peptide cyclization. First we show that given a linker sequence and the conformation of the linear peptide, it is possible to accurately predict the cyclized peptide conformation. Second, and more importantly, we show that it seems possible to elaborate on the information inferred from protein structures to propose effective candidate linker sequences constrained by length and amino acid composition, providing the first framework for the rational design of head-to-tail cyclization linkers. Finally, we illustrate this for two peptides using a limited set of amino-acids likely not to interfere with peptide function. For a linear peptide derived from Nrf2, the peptide cyclized starting from the experimental structure showed a 26-fold increase in the binding affinity. For urotensin II, a peptide already cyclized by a disulfide bond that exerts a broad array of biological activities, we were able, starting from models of the structure, to design a head-to-tail cyclized peptide, the first synthesized bicyclic 14-residue long urotensin II analogue, showing a retention of in vitro activity. Although preliminary, our results strongly suggest that such an approach has strong potential for cyclic peptide-based drug design.
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Affiliation(s)
- Yasaman Karami
- Université
Paris Cité, CNRS UMR 8251,
INSERM ERL U1133, 75013 Paris, France
| | - Samuel Murail
- Université
Paris Cité, CNRS UMR 8251,
INSERM ERL U1133, 75013 Paris, France
| | - Julien Giribaldi
- Institut
des Biomolécules Max Mousseron, UMR 5247, Université de Montpellier-CNRS, 34293 Montpellier, France
| | - Benjamin Lefranc
- Université
de Rouen Normandie, INSERM U1239 NorDiC, Neuroendocrine, Endocrine and Germinal Differentiation and Communication,
INSERM US51 HeRacLeS, F-76000 Rouen, France
| | - Florian Defontaine
- Université
de Rouen Normandie, UR CBSA, Research Unit
Bacterial Communication and Anti-infectious Strategies, 27000 Evreux, France
| | - Olivier Lesouhaitier
- Université
de Rouen Normandie, UR CBSA, Research Unit
Bacterial Communication and Anti-infectious Strategies, 27000 Evreux, France
| | - Jérôme Leprince
- Université
de Rouen Normandie, INSERM U1239 NorDiC, Neuroendocrine, Endocrine and Germinal Differentiation and Communication,
INSERM US51 HeRacLeS, F-76000 Rouen, France
| | - Sjoerd de Vries
- Université
Paris Cité, CNRS UMR 8251,
INSERM ERL U1133, 75013 Paris, France
| | - Pierre Tufféry
- Université
Paris Cité, CNRS UMR 8251,
INSERM ERL U1133, 75013 Paris, France
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2
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Tyler TJ, Durek T, Craik DJ. Native and Engineered Cyclic Disulfide-Rich Peptides as Drug Leads. Molecules 2023; 28:molecules28073189. [PMID: 37049950 PMCID: PMC10096437 DOI: 10.3390/molecules28073189] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 03/27/2023] [Accepted: 03/29/2023] [Indexed: 04/07/2023] Open
Abstract
Bioactive peptides are a highly abundant and diverse group of molecules that exhibit a wide range of structural and functional variation. Despite their immense therapeutic potential, bioactive peptides have been traditionally perceived as poor drug candidates, largely due to intrinsic shortcomings that reflect their endogenous heritage, i.e., short biological half-lives and poor cell permeability. In this review, we examine the utility of molecular engineering to insert bioactive sequences into constrained scaffolds with desired pharmaceutical properties. Applying lessons learnt from nature, we focus on molecular grafting of cyclic disulfide-rich scaffolds (naturally derived or engineered), shown to be intrinsically stable and amenable to sequence modifications, and their utility as privileged frameworks in drug design.
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Affiliation(s)
- Tristan J. Tyler
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Thomas Durek
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, Brisbane, QLD 4072, Australia
| | - David J. Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, Brisbane, QLD 4072, Australia
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3
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Rajendran S, Slazak B, Mohotti S, Muhammad T, Strömstedt AA, Kapusta M, Wilmowicz E, Göransson U, Hettiarachchi CM, Gunasekera S. Screening for Cyclotides in Sri Lankan Medicinal Plants: Discovery, Characterization, and Bioactivity Screening of Cyclotides from Geophila repens. JOURNAL OF NATURAL PRODUCTS 2023; 86:52-65. [PMID: 36525646 PMCID: PMC9887600 DOI: 10.1021/acs.jnatprod.2c00674] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Indexed: 06/17/2023]
Abstract
Cyclotides are an intriguing class of structurally stable circular miniproteins of plant origin with numerous potential pharmaceutical and agricultural applications. To investigate the occurrence of cyclotides in Sri Lankan flora, 50 medicinal plants were screened, leading to the identification of a suite of new cyclotides from Geophila repens of the family Rubiaceae. Cycloviolacin O2-like (cyO2-like) gere 1 and the known cyclotide kalata B7 (kB7) were among the cyclotides characterized at the peptide and/or transcript level together with several putative enzymes, likely involved in cyclotide biosynthesis. Five of the most abundant cyclotides were isolated, sequenced, structurally characterized, and screened in antimicrobial and cytotoxicity assays. All gere cyclotides showed cytotoxicity (IC50 of 2.0-10.2 μM), but only gere 1 inhibited standard microbial strains at a minimum inhibitory concentration of 4-16 μM. As shown by immunohistochemistry, large quantities of the cyclotides were localized in the epidermis of the leaves and petioles of G. repens. Taken together with the cytotoxicity and membrane permeabilizing activities, this implicates gere cyclotides as potential plant defense molecules. The presence of cyO2-like gere 1 in a plant in the Rubiaceae supports the notion that phylogenetically distant plants may have coevolved to express similar cytotoxic cyclotides for a specific functional role, most likely involving host defense.
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Affiliation(s)
- Sanjeevan Rajendran
- Phamacognosy,
Department of Pharmaceutical Biosciences, Uppsala University, Biomedical Centre, SE 75124 Uppsala, Sweden
- Department
of Chemistry, Faculty of Science, University
of Colombo, Thurstan Road, Colombo 00300, Sri Lanka
| | - Blazej Slazak
- Phamacognosy,
Department of Pharmaceutical Biosciences, Uppsala University, Biomedical Centre, SE 75124 Uppsala, Sweden
- W.
Szafer Institute of Botany of the Polish Academy of Sciences, 46 Lubicz, 31-512 Cracow, Poland
| | - Supun Mohotti
- Department
of Chemistry, Faculty of Science, University
of Colombo, Thurstan Road, Colombo 00300, Sri Lanka
| | - Taj Muhammad
- Phamacognosy,
Department of Pharmaceutical Biosciences, Uppsala University, Biomedical Centre, SE 75124 Uppsala, Sweden
| | - Adam A. Strömstedt
- Phamacognosy,
Department of Pharmaceutical Biosciences, Uppsala University, Biomedical Centre, SE 75124 Uppsala, Sweden
| | - Małgorzata Kapusta
- Department
of Plant Cytology and Embryology, Faculty of Biology, University of Gdańsk, 59 Wita Stwosza, 80-308 Gdańsk, Poland
| | - Emilia Wilmowicz
- Faculty
of Biological and Veterinary Sciences, Nicolaus
Copernicus University, 1 Lwowska Street, 87-100 Toruń, Poland
| | - Ulf Göransson
- Phamacognosy,
Department of Pharmaceutical Biosciences, Uppsala University, Biomedical Centre, SE 75124 Uppsala, Sweden
| | - Chamari M. Hettiarachchi
- Department
of Chemistry, Faculty of Science, University
of Colombo, Thurstan Road, Colombo 00300, Sri Lanka
| | - Sunithi Gunasekera
- Phamacognosy,
Department of Pharmaceutical Biosciences, Uppsala University, Biomedical Centre, SE 75124 Uppsala, Sweden
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4
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Fernández-Bobey A, Pinto MEF, de Almeida LC, de Souza BM, Dias NB, de Paula-Souza J, Cilli EM, Lopes NP, Costa-Lotufo LV, Palma MS, da Silva Bolzani V. Cytotoxic Cyclotides from Anchietea pyrifolia, a South American Plant Species. JOURNAL OF NATURAL PRODUCTS 2022; 85:2127-2134. [PMID: 36044031 DOI: 10.1021/acs.jnatprod.1c01129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Cyclotides are mini-proteins with potent bioactivities and outstanding potential for agricultural and pharmaceutical applications. More than 450 different plant cyclotides have been isolated from six angiosperm families. In Brazil, studies involving this class of natural products are still scarce, despite its rich floristic diversity. Herein were investigated the cyclotides from Anchietea pyrifolia roots, a South American medicinal plant from the family Violaceae. Fourteen putative cyclotides were annotated by LC-MS. Among these, three new bracelet cyclotides, anpy A-C, and the known cycloviolacins O4 (cyO4) and O17 (cyO17) were sequenced through a combination of chemical and enzymatic reactions followed by MALDI-MS/MS analysis. Their cytotoxic activity was evaluated by a cytotoxicity assay against three human cancer cell lines (colorectal carcinoma cells: HCT 116 and HCT 116 TP53-/- and breast adenocarcinoma, MCF 7). For all assays, the IC50 values of isolated compounds ranged between 0.8 and 7.3 μM. CyO17 was the most potent cyclotide for the colorectal cancer cell lines (IC50, 0.8 and 1.2 μM). Furthermore, the hemolytic activity of anpy A and B, cyO4, and cyO17 was assessed, and the cycloviolacins were the least hemolytic (HD50 > 156 μM). This work sheds light on the cytotoxic effects of the anpy cyclotides against cancer cells. Moreover, this study expands the number of cyclotides obtained to date from Brazilian plant biodiversity and adds one more genus containing these molecules to the list of the Violaceae family.
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Affiliation(s)
- Antonio Fernández-Bobey
- Nucleus of Bioassays, Biosynthesis, and Ecophysiology of Natural Products (NuBBE), Institute of Chemistry, Sao Paulo State University (UNESP), 14800-060, Araraquara, Sao Paulo, Brazil
- Department of Basic and Applied Biology, Laboratory of Structural Biology and Zoochemistry, Institute of Biosciences, Sao Paulo State University (UNESP), 13506-900, Rio Claro, Sao Paulo, Brazil
| | - Meri Emili Ferreira Pinto
- Nucleus of Bioassays, Biosynthesis, and Ecophysiology of Natural Products (NuBBE), Institute of Chemistry, Sao Paulo State University (UNESP), 14800-060, Araraquara, Sao Paulo, Brazil
| | - Larissa Costa de Almeida
- Department of Pharmacology, Institute of Biomedical Science, University of Sao Paulo (USP), 05508-900, Sao Paulo, Brazil
| | - Bibiana Monson de Souza
- Department of Basic and Applied Biology, Laboratory of Structural Biology and Zoochemistry, Institute of Biosciences, Sao Paulo State University (UNESP), 13506-900, Rio Claro, Sao Paulo, Brazil
| | - Nathalia Baptista Dias
- Scientific and Technological Bioresource Nucleus (BIOREN), University of The Frontier (UFRO), 4881-176, Temuco, Chile
| | - Juliana de Paula-Souza
- Department of Botany, Federal University of Santa Catarina (UFSC), 88040-535, Florianopolis, Santa Catarina, Brazil
| | - Eduardo Maffud Cilli
- Nucleus of Bioassays, Biosynthesis, and Ecophysiology of Natural Products (NuBBE), Institute of Chemistry, Sao Paulo State University (UNESP), 14800-060, Araraquara, Sao Paulo, Brazil
| | - Norberto Peporine Lopes
- Nucleus Research in Natural and Synthetic Products (NPPNS), Faculty of Pharmaceutical Sciences of Ribeirao Preto, University of Sao Paulo (USP), 14040-903, Ribeirao Preto, Sao Paulo, Brazil
| | - Leticia Veras Costa-Lotufo
- Department of Pharmacology, Institute of Biomedical Science, University of Sao Paulo (USP), 05508-900, Sao Paulo, Brazil
| | - Mario Sergio Palma
- Department of Basic and Applied Biology, Laboratory of Structural Biology and Zoochemistry, Institute of Biosciences, Sao Paulo State University (UNESP), 13506-900, Rio Claro, Sao Paulo, Brazil
| | - Vanderlan da Silva Bolzani
- Nucleus of Bioassays, Biosynthesis, and Ecophysiology of Natural Products (NuBBE), Institute of Chemistry, Sao Paulo State University (UNESP), 14800-060, Araraquara, Sao Paulo, Brazil
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5
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Taghizadeh MS, Retzl B, Muratspahić E, Trenk C, Casanova E, Moghadam A, Afsharifar A, Niazi A, Gruber CW. Discovery of the cyclotide caripe 11 as a ligand of the cholecystokinin-2 receptor. Sci Rep 2022; 12:9215. [PMID: 35654807 PMCID: PMC9163038 DOI: 10.1038/s41598-022-13142-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 05/20/2022] [Indexed: 11/08/2022] Open
Abstract
The cholecystokinin-2 receptor (CCK2R) is a G protein-coupled receptor (GPCR) that is expressed in peripheral tissues and the central nervous system and constitutes a promising target for drug development in several diseases, such as gastrointestinal cancer. The search for ligands of this receptor over the past years mainly resulted in the discovery of a set of distinct synthetic small molecule chemicals. Here, we carried out a pharmacological screening of cyclotide-containing plant extracts using HEK293 cells transiently-expressing mouse CCK2R, and inositol phosphate (IP1) production as a readout. Our data demonstrated that cyclotide-enriched plant extracts from Oldenlandia affinis, Viola tricolor and Carapichea ipecacuanha activate the CCK2R as measured by the production of IP1. These findings prompted the isolation of a representative cyclotide, namely caripe 11 from C. ipecacuanha for detailed pharmacological analysis. Caripe 11 is a partial agonist of the CCK2R (Emax = 71%) with a moderate potency of 8.5 µM, in comparison to the endogenous full agonist cholecystokinin-8 (CCK-8; EC50 = 11.5 nM). The partial agonism of caripe 11 is further characterized by an increase on basal activity (at low concentrations) and a dextral-shift of the potency of CCK-8 (at higher concentrations) following its co-incubation with the cyclotide. Therefore, cyclotides such as caripe 11 may be explored in the future for the design and development of cyclotide-based ligands or imaging probes targeting the CCK2R and related peptide GPCRs.
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Affiliation(s)
- Mohammad Sadegh Taghizadeh
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
- Institute of Biotechnology, Shiraz University, Shiraz, Iran
| | - Bernhard Retzl
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Edin Muratspahić
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Christoph Trenk
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Emilio Casanova
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Ali Moghadam
- Institute of Biotechnology, Shiraz University, Shiraz, Iran
| | | | - Ali Niazi
- Institute of Biotechnology, Shiraz University, Shiraz, Iran
| | - Christian W Gruber
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria.
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6
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Zhang J, Yuan J, Li Z, Fu C, Xu M, Yang J, Jiang X, Zhou B, Ye X, Xu C. Exploring and exploiting plant cyclic peptides for drug discovery and development. Med Res Rev 2021; 41:3096-3117. [PMID: 33599316 DOI: 10.1002/med.21792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 01/10/2021] [Accepted: 01/31/2021] [Indexed: 01/07/2023]
Abstract
Ever since the discovery of insulin, natural peptides have become an important resource for therapeutic development. Decades of research has led to the discovery of a long list of peptide drugs with broad applications in clinics, from antibiotics to hypertension treatment to pain management. Many of these US FDA-approved peptide drugs are derived from microorganisms and animals. By contrast, the great potential of plant cyclic peptides as therapeutics remains largely unexplored. These macrocyclic peptides typically have rigid structures, good bioavailability and membrane permeability, making them appealing candidates for drug development and engineering. In this review, we introduce the three major classes of plant cyclic peptides and summarize their potential medical applications. We discuss how we can leverage the genome information of many different plants to quickly search for new cyclic peptides and how we can take advantage of the insights gained from their biosynthetic pathways to transform the process of production and drug development. These recent developments have provided a new angle for exploring and exploiting plant cyclic peptides, and we believe that many more peptide drugs derived from plants are about to come.
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Affiliation(s)
- Jingjing Zhang
- Department of Geriatric Medicine, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China.,Integrated Chinese and Western Medicine Postdoctoral Research Station, Jinan University, Guangzhou, Guangdong, China
| | - Jimin Yuan
- Department of Geriatric Medicine, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China
| | - Zhijie Li
- Department of Geriatric Medicine, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China
| | - Chunjin Fu
- Department of Geriatric Medicine, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China
| | - Menglong Xu
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
| | - Jing Yang
- Department of Geriatric Medicine, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China
| | - Xin Jiang
- Department of Geriatric Medicine, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China
| | - Boping Zhou
- Department of Infectious Diseases, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China
| | - Xiufeng Ye
- Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China
| | - Chengchao Xu
- Department of Geriatric Medicine, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, Guangdong, China.,Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
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7
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Grover T, Mishra R, Gulati P, Mohanty A. An insight into biological activities of native cyclotides for potential applications in agriculture and pharmaceutics. Peptides 2021; 135:170430. [PMID: 33096195 DOI: 10.1016/j.peptides.2020.170430] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 10/06/2020] [Accepted: 10/12/2020] [Indexed: 02/08/2023]
Abstract
Cyclotides are plant-derived mini-proteins of 28 - 37 amino acids. They have a characteristic head-to-tail cyclic backbone and three disulfide cross-linkages formed by six highly conserved cysteine residues, creating a unique knotted ring structure, known as a cyclic cystine knot (CCK) motif. The CCK topology confers immense stability to cyclotides with resistance to thermal and enzymatic degradation. Native cyclotides are of interest due to their multiple biological activities with several potential applications in agricultural (e.g. biopesticides, antifungal) and pharmaceutical (e.g. anti-HIV, cytotoxic to tumor cells) sectors. The most recent application of insecticidal activity of cyclotides is the commercially available biopesticidal spray known as 'Sero X' for cotton crops. Cyclotides have a general mode of action and their potency of bioactivity is determined through their binding ability, pore formation and disruption of the target biological membranes. Keeping in view the important potential applications of biological activities of cyclotides and the lack of an extensive and analytical compilation of bioactive cyclotides, the present review systematically describes eight major biological activities of the native cyclotides from four angiosperm families viz. Fabaceae, Poaceae, Rubiaceae, Violaceae. The bioactivities of 94 cytotoxic, 57 antibacterial, 44 hemolytic, 25 antifungal, 21 anti-HIV, 20 nematocidal, 10 insecticidal and 5 molluscicidal cyclotides have been comprehensively elaborated. Further, their distribution in angiosperm families, mode of action and future prospects have also been discussed.
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Affiliation(s)
- Tripti Grover
- Bioinformatics Infrastructure Facility, Gargi College, University of Delhi, India
| | - Reema Mishra
- Department of Botany, Gargi College, University of Delhi, India
| | - Pooja Gulati
- Department of Microbiology, Maharshi Dayanand University, Rohtak, Haryana, India
| | - Aparajita Mohanty
- Bioinformatics Infrastructure Facility, Gargi College, University of Delhi, India.
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8
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Abstract
This Review explores the class of plant-derived macrocyclic peptides called cyclotides. We include an account of their discovery, characterization, and distribution in the plant kingdom as well as a detailed analysis of their sequences and structures, biosynthesis and chemical synthesis, biological functions, and applications. These macrocyclic peptides are around 30 amino acids in size and are characterized by their head-to-tail cyclic backbone and cystine knot motif, which render them to be exceptionally stable, with resistance to thermal or enzymatic degradation. Routes to their chemical synthesis have been developed over the past two decades, and this capability has facilitated a wide range of mutagenesis and structure-activity relationship studies. In turn, these studies have both led to an increased understanding of their mechanisms of action as well as facilitated a range of applications in agriculture and medicine, as ecofriendly crop protection agents, and as drug leads or scaffolds for pharmaceutical design. Our overall objective in this Review is to provide readers with a comprehensive overview of cyclotides that we hope will stimulate further work on this fascinating family of peptides.
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Affiliation(s)
- Simon J de Veer
- Institute for Molecular Bioscience , The University of Queensland , Brisbane , Queensland 4072 , Australia
| | - Meng-Wei Kan
- Institute for Molecular Bioscience , The University of Queensland , Brisbane , Queensland 4072 , Australia
| | - David J Craik
- Institute for Molecular Bioscience , The University of Queensland , Brisbane , Queensland 4072 , Australia
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9
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Huang YH, Du Q, Craik DJ. Cyclotides: Disulfide-rich peptide toxins in plants. Toxicon 2019; 172:33-44. [DOI: 10.1016/j.toxicon.2019.10.244] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/30/2019] [Accepted: 10/30/2019] [Indexed: 12/27/2022]
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10
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Chemical Synthesis and Functional Analysis of VarvA Cyclotide. Molecules 2018; 23:molecules23040952. [PMID: 29671790 PMCID: PMC6017059 DOI: 10.3390/molecules23040952] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 04/14/2018] [Accepted: 04/17/2018] [Indexed: 11/17/2022] Open
Abstract
Cyclotides are circular peptides found in various plant families. A cyclized backbone, together with multiple disulfide bonds, confers the peptides’ exceptional stability against protease digestion and thermal denaturation. In addition, the features of these antimicrobial molecules make them suitable for use in animal farming, such as aquaculture. Fmoc solid phase peptide synthesis on 2-chlorotrityl chlorine (CTC) resin using the “tea-bag” approach was conducted to generate the VarvA cyclotide identified previously from Viola arvensis. MALDI-TOF mass spectrometry determined the correct peptide amino acid sequence and the cyclization sites-critical in this multicyclic compound. The cyclotide showed antimicrobial activity against various Gram-negative bacteria, including recurrent pathogens present in Chilean aquaculture. The highest antimicrobial activity was found to be against Flavobacterium psychrophilum. In addition, membrane blebbing on the bacterial surface after exposure to the cyclotide was visualized by SEM microscopy and the Sytox Green permeabilization assay showed the ability to disrupt the bacterial membrane. We postulate that this compound can be proposed for the control of fish farming infections.
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11
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Bactericidal activity of cyclotides where phosphatidylethanolamine-lipid selectivity determines antimicrobial spectra. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1986-2000. [DOI: 10.1016/j.bbamem.2017.06.018] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 06/27/2017] [Accepted: 06/27/2017] [Indexed: 12/17/2022]
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12
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Fahradpour M, Keov P, Tognola C, Perez-Santamarina E, McCormick PJ, Ghassempour A, Gruber CW. Cyclotides Isolated from an Ipecac Root Extract Antagonize the Corticotropin Releasing Factor Type 1 Receptor. Front Pharmacol 2017; 8:616. [PMID: 29033832 PMCID: PMC5627009 DOI: 10.3389/fphar.2017.00616] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 08/23/2017] [Indexed: 12/22/2022] Open
Abstract
Cyclotides are plant derived, cystine-knot stabilized peptides characterized by their natural abundance, sequence variability and structural plasticity. They are abundantly expressed in Rubiaceae, Psychotrieae in particular. Previously the cyclotide kalata B7 was identified to modulate the human oxytocin and vasopressin G protein-coupled receptors (GPCRs), providing molecular validation of the plants' uterotonic properties and further establishing cyclotides as valuable source for GPCR ligand design. In this study we screened a cyclotide extract derived from the root powder of the South American medicinal plant ipecac (Carapichea ipecacuanha) for its GPCR modulating activity of the corticotropin-releasing factor type 1 receptor (CRF1R). We identified and characterized seven novel cyclotides. One cyclotide, caripe 8, isolated from the most active fraction, was further analyzed and found to antagonize the CRF1R. A nanomolar concentration of this cyclotide (260 nM) reduced CRF potency by ∼4.5-fold. In contrast, caripe 8 did not inhibit forskolin-, or vasopressin-stimulated cAMP responses at the vasopressin V2 receptor, suggesting a CRF1R-specific mode-of-action. These results in conjunction with our previous findings establish cyclotides as modulators of both classes A and B GPCRs. Given the diversity of cyclotides, our data point to other cyclotide-GPCR interactions as potentially important sources of drug-like molecules.
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Affiliation(s)
- Mohsen Fahradpour
- Center for Physiology and Pharmacology, Medical University of ViennaVienna, Austria.,Medicinal Plants and Drugs Research Institute, Shahid Beheshti UniversityTehran, Iran
| | - Peter Keov
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, BrisbaneQLD, Australia
| | - Carlotta Tognola
- Center for Physiology and Pharmacology, Medical University of ViennaVienna, Austria
| | | | - Peter J McCormick
- School of Veterinary Medicine, University of SurreyGuildford, United Kingdom
| | - Alireza Ghassempour
- Medicinal Plants and Drugs Research Institute, Shahid Beheshti UniversityTehran, Iran
| | - Christian W Gruber
- Center for Physiology and Pharmacology, Medical University of ViennaVienna, Austria.,Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, BrisbaneQLD, Australia
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13
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Craik DJ, Lee MH, Rehm FBH, Tombling B, Doffek B, Peacock H. Ribosomally-synthesised cyclic peptides from plants as drug leads and pharmaceutical scaffolds. Bioorg Med Chem 2017; 26:2727-2737. [PMID: 28818463 DOI: 10.1016/j.bmc.2017.08.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/12/2017] [Accepted: 08/06/2017] [Indexed: 12/28/2022]
Abstract
Owing to their exceptional stability and favourable pharmacokinetic properties, plant-derived cyclic peptides have recently attracted significant attention in the field of peptide-based drug design. This article describes the three major classes of ribosomally-synthesised plant peptides - the cyclotides, the PawS-derived peptides and the orbitides - and reviews their applications as leads or scaffolds in drug design. These ribosomally-produced peptides have a range of biological activities, including anti-HIV, cytotoxic and immunomodulatory activity. In addition, recent interest has focused on their use as scaffolds to stabilise bioactive peptide sequences, thereby enhancing their biopharmaceutical properties. There are now more than 30 published papers on such 'grafting' applications, most of which have been reported only in the last few years, and several such studies have reported in vivo activity of orally delivered cyclic peptides. In this article, we describe approaches to the synthesis of cyclic peptides and their pharmaceutically-grafted derivatives as well as outlining their biosynthetic routes. Finally, we describe possible bioproduction routes for pharmaceutically active cyclic peptides, involving plants and plant suspension cultures.
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Affiliation(s)
- David J Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
| | - Meng-Han Lee
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Fabian B H Rehm
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Benjamin Tombling
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Benjamin Doffek
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Hayden Peacock
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
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14
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Cyclotides as drug design scaffolds. Curr Opin Chem Biol 2017; 38:8-16. [DOI: 10.1016/j.cbpa.2017.01.018] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 01/27/2017] [Indexed: 11/21/2022]
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15
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Troeira Henriques S, Craik DJ. Cyclotide Structure and Function: The Role of Membrane Binding and Permeation. Biochemistry 2017; 56:669-682. [DOI: 10.1021/acs.biochem.6b01212] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sónia Troeira Henriques
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, 4072 QLD, Australia
| | - David J. Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, 4072 QLD, Australia
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16
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Molesini B, Treggiari D, Dalbeni A, Minuz P, Pandolfini T. Plant cystine-knot peptides: pharmacological perspectives. Br J Clin Pharmacol 2017; 83:63-70. [PMID: 26987851 PMCID: PMC5338163 DOI: 10.1111/bcp.12932] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 03/07/2016] [Accepted: 03/09/2016] [Indexed: 12/29/2022] Open
Abstract
Cystine-knot miniproteins are a class of 30-50 amino acid long peptides widespread in eukaryotic organisms. Due to their very peculiar three-dimensional structure, they exhibit high resistance to heat and peptidase attack. The cystine-knot peptides are well represented in several plant species including medicinal herbs and crops. The pharmacological interest in plant cystine-knot peptides derives from their broad biological activities, mainly cytotoxic, antimicrobial and peptidase inhibitory and in the possibility to engineer them to incorporate pharmacophoric information for oral delivery or disease biomonitoring. The mechanisms of action of plant cystine-knot peptides are still largely unknown, although the capacity to interfere with plasma membranes seems a feature common to several cystine-knot peptides. In some cases, such as potato carboxypetidase inhibitor (PCI) and tomato cystine-knot miniproteins (TCMPs), the cystine-knot peptides target human growth factor receptors either by acting as growth factor antagonist or by altering their signal transduction pathway. The possibility to identify specific molecular targets of plant cystine-knot peptides in human cells opens novel possibilities for the pharmacological use of these peptides besides their use as scaffold to develop stable disease molecular markers and therapeutic agents.
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Affiliation(s)
| | - Davide Treggiari
- Department of Medicine, Section of Internal MedicineUniversity of VeronaVeronaItaly
| | - Andrea Dalbeni
- Department of Medicine, Section of Internal MedicineUniversity of VeronaVeronaItaly
| | - Pietro Minuz
- Department of Medicine, Section of Internal MedicineUniversity of VeronaVeronaItaly
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17
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Slazak B, Kapusta M, Malik S, Bohdanowicz J, Kuta E, Malec P, Göransson U. Immunolocalization of cyclotides in plant cells, tissues and organ supports their role in host defense. PLANTA 2016; 244:1029-1040. [PMID: 27394154 PMCID: PMC5052299 DOI: 10.1007/s00425-016-2562-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 06/20/2016] [Indexed: 05/02/2023]
Abstract
The distribution of cyclotides was visualized in plant cells, tissues and organs using immunohistochemistry. Finding of cyclotides in tissues potentially vulnerable to pathogen attacks supports their role as defense molecules. The cyclotide family of plant peptides is characterized by the cyclic cystine knot motif and its diverse biological activities. Given their insecticidal and antimicrobial properties, the role of cyclotides in planta is probably associated with host defense. Our current understanding of the cellular compartmentalization of cyclotides in the vacuole is based on indirect studies on transgenic model plants that do not express cyclotides naturally. Matrix-assisted laser desorption ionization (MALDI) imaging has also been used to study the distribution of cyclotides, but the technique's resolution was insufficient to determine their tissue or cell distribution. To avoid the limitations of these approaches, immunohistochemical visualization methods were used. Antibodies were raised in rabbits using cycloviolacin O2 (cyO2), and their specificity was determined by Western and dot blot experiments. Slides for immunohistochemical analysis were prepared from leaf, petiole and root fragments of Viola odorata and Viola uliginosa, and specimens were visualized using indirect epifluorescence microscopy. The antibodies against cyclotides were specific against selected bracelet cyclotides with high similarity (cyO2, cyO3, cyO8, cyO13) and suitable for immunohistochemistry. The tissue distribution of the cyclotides visualized in this way is consistent with their proposed role in host defense-relatively large quantities were observed in the leaf and petiole epidermis in both Viola species. Cyclotides were also found in vascular tissue in all the assessed plant organs. The vacuole storage of cyclotides was directly shown.
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Affiliation(s)
- Blazej Slazak
- W. Szafer Institute of Botany, Polish Academy of Science, 46 Lubicz St, 31-512, Cracow, Poland.
- Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Center, Box 574, 751 23, Uppsala, Sweden.
| | - Małgorzata Kapusta
- Department of Plant Cytology and Embryology, Faculty of Biology, University of Gdańsk, 59 Wita Stwosza St, 80-308, Gdańsk, Poland
| | - Sohaib Malik
- Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Center, Box 574, 751 23, Uppsala, Sweden
| | - Jerzy Bohdanowicz
- Department of Plant Cytology and Embryology, Faculty of Biology, University of Gdańsk, 59 Wita Stwosza St, 80-308, Gdańsk, Poland
| | - Elżbieta Kuta
- Department of Plant Cytology and Embryology, Institute of Botany, Jagiellonian University, 9 Gronostajowa St, 30-387, Cracow, Poland
| | - Przemysław Malec
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 7 Gronostajowa St, 30-387, Cracow, Poland
| | - Ulf Göransson
- Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Center, Box 574, 751 23, Uppsala, Sweden
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18
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Slazak B, Kapusta M, Malik S, Bohdanowicz J, Kuta E, Malec P, Göransson U. Immunolocalization of cyclotides in plant cells, tissues and organ supports their role in host defense. PLANTA 2016. [PMID: 27394154 DOI: 10.1016/10.1007/s00425-016-2562-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The distribution of cyclotides was visualized in plant cells, tissues and organs using immunohistochemistry. Finding of cyclotides in tissues potentially vulnerable to pathogen attacks supports their role as defense molecules. The cyclotide family of plant peptides is characterized by the cyclic cystine knot motif and its diverse biological activities. Given their insecticidal and antimicrobial properties, the role of cyclotides in planta is probably associated with host defense. Our current understanding of the cellular compartmentalization of cyclotides in the vacuole is based on indirect studies on transgenic model plants that do not express cyclotides naturally. Matrix-assisted laser desorption ionization (MALDI) imaging has also been used to study the distribution of cyclotides, but the technique's resolution was insufficient to determine their tissue or cell distribution. To avoid the limitations of these approaches, immunohistochemical visualization methods were used. Antibodies were raised in rabbits using cycloviolacin O2 (cyO2), and their specificity was determined by Western and dot blot experiments. Slides for immunohistochemical analysis were prepared from leaf, petiole and root fragments of Viola odorata and Viola uliginosa, and specimens were visualized using indirect epifluorescence microscopy. The antibodies against cyclotides were specific against selected bracelet cyclotides with high similarity (cyO2, cyO3, cyO8, cyO13) and suitable for immunohistochemistry. The tissue distribution of the cyclotides visualized in this way is consistent with their proposed role in host defense-relatively large quantities were observed in the leaf and petiole epidermis in both Viola species. Cyclotides were also found in vascular tissue in all the assessed plant organs. The vacuole storage of cyclotides was directly shown.
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Affiliation(s)
- Blazej Slazak
- W. Szafer Institute of Botany, Polish Academy of Science, 46 Lubicz St, 31-512, Cracow, Poland.
- Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Center, Box 574, 751 23, Uppsala, Sweden.
| | - Małgorzata Kapusta
- Department of Plant Cytology and Embryology, Faculty of Biology, University of Gdańsk, 59 Wita Stwosza St, 80-308, Gdańsk, Poland
| | - Sohaib Malik
- Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Center, Box 574, 751 23, Uppsala, Sweden
| | - Jerzy Bohdanowicz
- Department of Plant Cytology and Embryology, Faculty of Biology, University of Gdańsk, 59 Wita Stwosza St, 80-308, Gdańsk, Poland
| | - Elżbieta Kuta
- Department of Plant Cytology and Embryology, Institute of Botany, Jagiellonian University, 9 Gronostajowa St, 30-387, Cracow, Poland
| | - Przemysław Malec
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 7 Gronostajowa St, 30-387, Cracow, Poland
| | - Ulf Göransson
- Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Center, Box 574, 751 23, Uppsala, Sweden
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19
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Poth AG, Chan LY, Craik DJ. Cyclotides as grafting frameworks for protein engineering and drug design applications. Biopolymers 2016; 100:480-91. [PMID: 23893608 DOI: 10.1002/bip.22284] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 04/30/2013] [Accepted: 05/07/2013] [Indexed: 11/08/2022]
Abstract
Cyclotides are a family of naturally occurring backbone-cyclized macrocyclic mini-proteins from plants that have a knotted trio of intramolecular disulfide bonds. Their structural features imbue cyclotides with extraordinary stability against degradation at elevated temperatures or in the presence of proteolytic enzymes. The plasticity of their intracysteine loop sequences is exemplified by the more than 250 natural cyclotides sequenced to date, and this tolerance to sequence variation, along with their diverse bioactivities, underpins the suitability of the cyclic cystine knot motif as a valuable drug design scaffold and research tool for protein engineering studies. Here, we review the recent literature on applications of cyclotides for the stabilization of peptide epitopes and related protein engineering studies. Possible future directions in this field are also described.
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Affiliation(s)
- Aaron G Poth
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, 4072, Australia
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20
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Strömstedt AA, Kristiansen PE, Gunasekera S, Grob N, Skjeldal L, Göransson U. Selective membrane disruption by the cyclotide kalata B7: complex ions and essential functional groups in the phosphatidylethanolamine binding pocket. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1317-27. [PMID: 26878982 DOI: 10.1016/j.bbamem.2016.02.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 02/10/2016] [Accepted: 02/11/2016] [Indexed: 01/17/2023]
Abstract
The cyclic cystine knot plant peptides called cyclotides are active against a wide variety of organisms. This is primarily achieved through membrane binding and disruption, in part deriving from a high affinity for phosphatidylethanolamine (PE) lipids. Some cyclotides, such as kalata B7 (kB7), form complexes with divalent cations in a pocket associated with the tyrosine residue at position 15 (Tyr15). In the current work we explore the effect of cations on membrane leakage caused by cyclotides kB1, kB2 and kB7, and we identify a functional group that is essential for PE selectivity. The presence of PE-lipids in liposomes increased the membrane permeabilizing potency of the cyclotides, with the potency of kB7 increasing by as much as 740-fold. The divalent cations Mn(2+), Mg(2+) and Ca(2+) had no apparent effect on PE selectivity. However, amino acid substitutions in kB7 proved that Tyr15 is crucial for PE-selective membrane permeabilization on various liposome systems. Although the tertiary structure of kB7 was maintained, as reflected by the NMR solution structure, mutating Tyr into Ser at position 15 resulted in substantially reduced PE selectivity. Ala substitution at the same position produced a similar reduction in PE selectivity, while substitution with Phe maintained high selectivity. We conclude that the phenyl ring in Tyr15 is critical for the high PE selectivity of kB7. Our results suggest that PE-binding and divalent cation coordination occur in the same pocket without adverse effects of competitive binding for the phospholipid.
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Affiliation(s)
- Adam A Strömstedt
- Department of Medicinal Chemistry, Division of Pharmacognosy, Uppsala University, Box 574, SE 75123 Uppsala, Sweden
| | - Per Eugen Kristiansen
- Department of Molecular Biosciences, University of Oslo, Box 1041, 0316 Oslo, Norway
| | - Sunithi Gunasekera
- Department of Medicinal Chemistry, Division of Pharmacognosy, Uppsala University, Box 574, SE 75123 Uppsala, Sweden
| | - Nathalie Grob
- Department of Medicinal Chemistry, Division of Pharmacognosy, Uppsala University, Box 574, SE 75123 Uppsala, Sweden
| | - Lars Skjeldal
- Department of Chemistry, Biochemistry and Food Science, Norwegian University of Life Sciences, N-1432 Ås, Norway
| | - Ulf Göransson
- Department of Medicinal Chemistry, Division of Pharmacognosy, Uppsala University, Box 574, SE 75123 Uppsala, Sweden
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21
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Tam JP, Wang S, Wong KH, Tan WL. Antimicrobial Peptides from Plants. Pharmaceuticals (Basel) 2015; 8:711-57. [PMID: 26580629 PMCID: PMC4695807 DOI: 10.3390/ph8040711] [Citation(s) in RCA: 283] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 08/06/2015] [Accepted: 09/01/2015] [Indexed: 12/25/2022] Open
Abstract
Plant antimicrobial peptides (AMPs) have evolved differently from AMPs from other life forms. They are generally rich in cysteine residues which form multiple disulfides. In turn, the disulfides cross-braced plant AMPs as cystine-rich peptides to confer them with extraordinary high chemical, thermal and proteolytic stability. The cystine-rich or commonly known as cysteine-rich peptides (CRPs) of plant AMPs are classified into families based on their sequence similarity, cysteine motifs that determine their distinctive disulfide bond patterns and tertiary structure fold. Cystine-rich plant AMP families include thionins, defensins, hevein-like peptides, knottin-type peptides (linear and cyclic), lipid transfer proteins, α-hairpinin and snakins family. In addition, there are AMPs which are rich in other amino acids. The ability of plant AMPs to organize into specific families with conserved structural folds that enable sequence variation of non-Cys residues encased in the same scaffold within a particular family to play multiple functions. Furthermore, the ability of plant AMPs to tolerate hypervariable sequences using a conserved scaffold provides diversity to recognize different targets by varying the sequence of the non-cysteine residues. These properties bode well for developing plant AMPs as potential therapeutics and for protection of crops through transgenic methods. This review provides an overview of the major families of plant AMPs, including their structures, functions, and putative mechanisms.
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Affiliation(s)
- James P Tam
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Shujing Wang
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
- Department of Pharmacology and Pharmaceutical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China.
| | - Ka H Wong
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Wei Liang Tan
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
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22
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Phoenix DA, Harris F, Mura M, Dennison SR. The increasing role of phosphatidylethanolamine as a lipid receptor in the action of host defence peptides. Prog Lipid Res 2015; 59:26-37. [PMID: 25936689 DOI: 10.1016/j.plipres.2015.02.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 02/26/2015] [Accepted: 02/27/2015] [Indexed: 01/04/2023]
Abstract
Host defence peptides (HDPs) are antimicrobial agents produced by organisms across the prokaryotic and eukaryotic kingdoms. Many prokaryotes produce HDPs, which utilise lipid and protein receptors in the membranes of bacterial competitors to facilitate their antibacterial action and thereby survive in their niche environment. As a major example, it is well established that cinnamycin and duramycins from Streptomyces have a high affinity for phosphatidylethanolamine (PE) and exhibit activity against other Gram-positive organisms, such as Bacillus. In contrast, although eukaryotic HDPs utilise membrane interactive mechanisms to facilitate their antimicrobial activity, the prevailing view has long been that these mechanisms do not involve membrane receptors. However, this view has been recently challenged by reports that a number of eukaryotic HDPs such as plant cyclotides also use PE as a receptor to promote their antimicrobial activities. Here, we review current understanding of the mechanisms that underpin the use of PE as a receptor in the antimicrobial and other biological actions of HDPs and describe medical and biotechnical uses of these peptides, which range from tumour imaging and detection to inclusion in topical microbicidal gels to prevent the sexual transmission of HIV.
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Affiliation(s)
- David A Phoenix
- School of Applied Science, London South Bank University, 103 Borough Road, London SE1 0AA, UK.
| | - Frederick Harris
- School of Applied Science, London South Bank University, 103 Borough Road, London SE1 0AA, UK; School of Forensic and Investigative Science, University of Central Lancashire, Preston PR1 2HE, UK
| | - Manuela Mura
- School of Mathematics and Physics, College of Science, University of Lincoln, Brayford Pool, Lincoln, Lincolnshire LN6 7TS, UK
| | - Sarah R Dennison
- School of Applied Science, London South Bank University, 103 Borough Road, London SE1 0AA, UK; School of Pharmacy and Biomedical Sciences, University of Central Lancashire, Preston PR1 2HE, UK
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23
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Koehbach J, Attah AF, Berger A, Hellinger R, Kutchan TM, Carpenter EJ, Rolf M, Sonibare MA, Moody JO, Ka-Shu Wong G, Dessein S, Greger H, Gruber CW. Cyclotide discovery in Gentianales revisited--identification and characterization of cyclic cystine-knot peptides and their phylogenetic distribution in Rubiaceae plants. Biopolymers 2013; 100:438-52. [PMID: 23897543 PMCID: PMC3816352 DOI: 10.1002/bip.22328] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 06/07/2013] [Indexed: 11/06/2022]
Abstract
Cyclotides are a unique class of ribosomally synthesized cysteine-rich miniproteins characterized by a head-to-tail cyclized backbone and three conserved disulfide-bonds in a knotted arrangement. Originally they were discovered in the coffee-family plant Oldenlandia affinis (Rubiaceae) and have since been identified in several species of the violet, cucurbit, pea, potato, and grass families. However, the identification of novel cyclotide-containing plant species still is a major challenge due to the lack of a rapid and accurate analytical workflow in particular for large sampling numbers. As a consequence, their phylogeny in the plant kingdom remains unclear. To gain further insight into the distribution and evolution of plant cyclotides, we analyzed ∼300 species of >40 different families, with special emphasis on plants from the order Gentianales. For this purpose, we have developed a refined screening methodology combining chemical analysis of plant extracts and bioinformatic analysis of transcript databases. Using mass spectrometry and transcriptome-mining, we identified nine novel cyclotide-containing species and their related cyclotide precursor genes in the tribe Palicoureeae. The characterization of novel peptide sequences underlines the high variability and plasticity of the cyclotide framework, and a comparison of novel precursor proteins from Carapichea ipecacuanha illustrated their typical cyclotide gene architectures. Phylogenetic analysis of their distribution within the Psychotria alliance revealed cyclotides to be restricted to Palicourea, Margaritopsis, Notopleura, Carapichea, Chassalia, and Geophila. In line with previous reports, our findings confirm cyclotides to be one of the largest peptide families within the plant kingdom and suggest that their total number may exceed tens of thousands.
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Affiliation(s)
- Johannes Koehbach
- Center for Physiology and Pharmacology, Medical University of Vienna, Schwarzspanierstrasse 17, 1090 Vienna, Austria
| | - Alfred F. Attah
- Center for Physiology and Pharmacology, Medical University of Vienna, Schwarzspanierstrasse 17, 1090 Vienna, Austria
- Department of Pharmacognosy, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria
| | - Andreas Berger
- Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, 1030 Vienna, Austria
| | - Roland Hellinger
- Center for Physiology and Pharmacology, Medical University of Vienna, Schwarzspanierstrasse 17, 1090 Vienna, Austria
| | | | - Eric J. Carpenter
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
- Department of Medicine, University of Alberta, Edmonton, AB, Canada
| | - Megan Rolf
- Donald Danforth Plant Science Center, St. Louis, MO
| | - Mubo A. Sonibare
- Department of Pharmacognosy, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria
| | - Jones O. Moody
- Department of Pharmacognosy, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria
| | - Gane Ka-Shu Wong
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
- Department of Medicine, University of Alberta, Edmonton, AB, Canada
- BGI-Shenzhen, Bei Shan Industrial Zone, Yantian District, Shenzhen, China
| | - Steven Dessein
- National Botanic Garden of Belgium, Domein van Bouchout, 1860 Meise, Belgium
| | - Harald Greger
- Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, 1030 Vienna, Austria
| | - Christian W. Gruber
- Center for Physiology and Pharmacology, Medical University of Vienna, Schwarzspanierstrasse 17, 1090 Vienna, Austria
- Department of Pharmacognosy, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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24
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Zarrabi M, Dalirfardouei R, Sepehrizade Z, Kermanshahi R. Comparison of the antimicrobial effects of semipurified cyclotides from Iranian Viola odorata
against some of plant and human pathogenic bacteria. J Appl Microbiol 2013; 115:367-75. [DOI: 10.1111/jam.12251] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 04/01/2013] [Accepted: 04/17/2013] [Indexed: 11/28/2022]
Affiliation(s)
- M. Zarrabi
- Department of Biology; Faculty of Science; Alzahra University; Tehran Iran
| | - R. Dalirfardouei
- Department of Biology; Faculty of Science; Alzahra University; Tehran Iran
| | - Z. Sepehrizade
- Department of Biotechnology; Faculty of Pharmacy; Tehran University; Tehran Iran
| | - R.K. Kermanshahi
- Department of Biology; Faculty of Science; Alzahra University; Tehran Iran
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25
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Making Ends Meet: Microwave-Accelerated Synthesis of Cyclic and Disulfide Rich Proteins Via In Situ Thioesterification and Native Chemical Ligation. Int J Pept Res Ther 2012; 19:43-54. [PMID: 23504256 PMCID: PMC3597280 DOI: 10.1007/s10989-012-9331-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2012] [Indexed: 12/21/2022]
Abstract
The development of synthetic methodologies for cyclic peptides is driven by the discovery of cyclic peptide drug scaffolds such as the plant-derived cyclotides, sunflower trypsin inhibitor 1 (SFTI-1) and the development of cyclized conotoxins. Currently, the native chemical ligation reaction between an N-terminal cysteine and C-terminal thioester group remains the most robust method to obtain a head-to-tail cyclized peptide. Peptidyl thioesters are effectively generated by Boc SPPS. However, their generation is challenging using Fmoc SPPS because thioester linkers are not stable to repeated piperidine exposure during deprotection. Herein we describe a Fmoc-based protocol for synthesizing cyclic peptides adapted for microwave assisted solid phase peptide synthesis. The protocol relies on the linker Di-Fmoc-3,4-diaminobenzoic acid, and we demonstrate the use of Gly, Ser, Arg and Ile as C-terminal amino acids (using HBTU and HATU as coupling reagents). Following synthesis, an N-acylurea moiety is generated at the C-terminal of the peptide; the resin bound acylurea peptide is then deprotected and cleaved from the resin. The fully deprotected peptide undergoes thiolysis in aqueous buffer, generating the thioester in situ. Ultimately, the head-to-tail cyclized peptide is obtained via native chemical ligation. Two naturally occurring cyclic peptides, the prototypical Möbius cyclotide kalata B1 and SFTI-1 were synthesized efficiently, avoiding potential branching at the diamino linker, using the optimized protocol. In addition, we demonstrate the possibility to use the approach for the synthesis of long and synthetically challenging linear sequences, by the ligation of two truncated fragments of a 50-residue long plant defensin.
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26
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Gould A, Ji Y, Aboye TL, Camarero JA. Cyclotides, a novel ultrastable polypeptide scaffold for drug discovery. Curr Pharm Des 2012; 17:4294-307. [PMID: 22204428 DOI: 10.2174/138161211798999438] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2011] [Accepted: 09/15/2011] [Indexed: 11/22/2022]
Abstract
Cyclotides are a unique and growing family of backbone cyclized peptides that also contain a cystine knot motif built from six conserved cysteine residues. This unique circular backbone topology and knotted arrangement of three disulfide bonds makes them exceptionally stable to thermal, chemical, and enzymatic degradation compared to other peptides of similar size. Aside from the conserved residues forming the cystine knot, cyclotides have been shown to have high variability in their sequences. Consisting of over 160 known members, cyclotides have many biological activities, ranging from anti-HIV, antimicrobial, hemolytic, and uterotonic capabilities; additionally, some cyclotides have been shown to have cell penetrating properties. Originally discovered and isolated from plants, cyclotides can also be produced synthetically and recombinantly. The high sequence variability, stability, and cell penetrating properties of cyclotides make them potential scaffolds to be used to graft known active peptides or engineer peptide-based drug design. The present review reports recent findings in the biological diversity and therapeutic potential of natural and engineered cyclotides.
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Affiliation(s)
- Andrew Gould
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90033, USA
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Wong CTT, Rowlands DK, Wong CH, Lo TWC, Nguyen GKT, Li HY, Tam JP. Orally Active Peptidic Bradykinin B1 Receptor Antagonists Engineered from a Cyclotide Scaffold for Inflammatory Pain Treatment. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201200984] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Wong CTT, Rowlands DK, Wong CH, Lo TWC, Nguyen GKT, Li HY, Tam JP. Orally Active Peptidic Bradykinin B1 Receptor Antagonists Engineered from a Cyclotide Scaffold for Inflammatory Pain Treatment. Angew Chem Int Ed Engl 2012; 51:5620-4. [DOI: 10.1002/anie.201200984] [Citation(s) in RCA: 183] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Indexed: 01/06/2023]
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Henriques ST, Craik DJ. Importance of the cell membrane on the mechanism of action of cyclotides. ACS Chem Biol 2012; 7:626-36. [PMID: 22260456 DOI: 10.1021/cb200395f] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Their distinctive structures, diverse range of bioactivities, and potential for pharmaceutical or agricultural applications make cyclotides an intriguing family of cyclic peptides. Together with the physiological role in plant host defense, cyclotides possess antimicrobial, anticancer, and anti-HIV activities. In all of the reported activities, cell membranes seem to be the primary target for cyclotide binding. This article examines recent literature on cyclotide-membrane studies and highlights the hypothesis that the activity of cyclotides is dependent on their affinity for lipid bilayers and enhanced by the presence of specific lipids, i.e., phospholipids containing phosphatidylethanolamine headgroups. There is growing evidence that the lipid composition of target cell membranes dictates the amount of cyclotides bound to the cell and the extent of their activity. After membrane targeting and insertion in the bilayer core, cyclotides induce disruption of membranes by a pore formation mechanism. This proposed mechanism of action is supported by biophysical studies with model membranes and by studies on natural biological membranes of known lipid compositions.
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Affiliation(s)
- Sónia Troeira Henriques
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
- Institute of Molecular Medicine,
Medical School, University of Lisbon, 1649-028
Lisbon, Portugal
| | - David J. Craik
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
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Gründemann C, Koehbach J, Huber R, Gruber CW. Do plant cyclotides have potential as immunosuppressant peptides? JOURNAL OF NATURAL PRODUCTS 2012; 75:167-74. [PMID: 22272797 PMCID: PMC3399773 DOI: 10.1021/np200722w] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cyclotides are an abundant and diverse group of ribosomally synthesized plant peptides containing a cyclic cystine-knotted structure that confers them with remarkable stability. They are explored for their distribution in plants, although little is known about the individual peptide content of a single species. Therefore, we chemically analyzed the crude extract of the coffee-family plant Oldenlandia affinis using a rapid peptidomics workflow utilizing nano-LC-MS, peptide reconstruct with database identification, and MS/MS automated sequence analysis to determine its cyclotide content. Biologically, cyclotides are mainly explored for applications in agriculture and drug design; here we report their growth-inhibiting effects on primary cells of the human immune system using biological and immunological end points in cell-based test systems. LC-MS quantification of the active O. affinis plant extract triggered the characterization of the antiproliferative activity of kalata B1, one of the most abundant cyclotides in this extract, on primary activated human lymphocytes. The effect has a defined concentration range and was not due to cytotoxicity, thus opening a new avenue to utilize native and synthetically optimized plant cyclotides for applications in immune-related disorders and as immunosuppressant peptides.
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Affiliation(s)
- Carsten Gründemann
- Center for Complementary Medicine, Department of Environmental Health Sciences, University Medical Center Freiburg, Breisacher Straße 115B, D-79111 Freiburg, Germany
| | - Johannes Koehbach
- Center for Physiology and Pharmacology, Medical University of Vienna, Schwarzspanierstraße 17, A-1090 Vienna, Austria
| | - Roman Huber
- Center for Complementary Medicine, Department of Environmental Health Sciences, University Medical Center Freiburg, Breisacher Straße 115B, D-79111 Freiburg, Germany
| | - Christian W Gruber
- Center for Physiology and Pharmacology, Medical University of Vienna, Schwarzspanierstraße 17, A-1090 Vienna, Austria
- Corresponding Author: Tel: +43-(0)1-4277-62511. Fax: +43-(0)1-4277-9623.
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Craik DJ. Host-defense activities of cyclotides. Toxins (Basel) 2012; 4:139-56. [PMID: 22474571 PMCID: PMC3317112 DOI: 10.3390/toxins4020139] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 01/25/2012] [Accepted: 01/31/2012] [Indexed: 11/27/2022] Open
Abstract
Cyclotides are plant mini-proteins whose natural function is thought to be to protect plants from pest or pathogens, particularly insect pests. They are approximately 30 amino acids in size and are characterized by a cyclic peptide backbone and a cystine knot arrangement of three conserved disulfide bonds. This article provides an overview of the reported pesticidal or toxic activities of cyclotides, discusses a possible common mechanism of action involving disruption of biological membranes in pest species, and describes methods that can be used to produce cyclotides for potential applications as novel pesticidal agents.
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Affiliation(s)
- David J Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
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Kimura RH, Teed R, Hackel BJ, Pysz MA, Chuang CZ, Sathirachinda A, Willmann JK, Gambhir SS. Pharmacokinetically stabilized cystine knot peptides that bind alpha-v-beta-6 integrin with single-digit nanomolar affinities for detection of pancreatic cancer. Clin Cancer Res 2011; 18:839-49. [PMID: 22173551 DOI: 10.1158/1078-0432.ccr-11-1116] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PURPOSE Detection of pancreatic cancer remains a high priority and effective diagnostic tools are needed for clinical applications. Many cancer cells overexpress integrin α(v)β(6), a cell surface receptor being evaluated as a novel clinical biomarker. EXPERIMENTAL DESIGN To validate this molecular target, several highly stable cystine knot peptides were engineered by directed evolution to bind specifically and with high affinity (3-6 nmol/L) to integrin α(v)β(6). The binders do not cross-react with related integrin α(v)β(5), integrin α(5)β(1), or tumor-angiogenesis-associated integrin, α(v)β(3). RESULTS Positron emission tomography showed that these disulfide-stabilized peptides rapidly accumulate at tumors expressing integrin α(v)β(6). Clinically relevant tumor-to-muscle ratios of 7.7 ± 2.4 to 11.3 ± 3.0 were achieved within 1 hour after radiotracer injection. Minimization of off-target dosing was achieved by reformatting α(v)β(6)-binding activities across various natural and pharmacokinetically stabilized cystine knot scaffolds with different amino acid content. We show that the primary sequence of a peptide scaffold directs its pharmacokinetics. Scaffolds with high arginine or glutamic acid content suffered high renal retention of more than 75% injected dose per gram (%ID/g). Substitution of these amino acids with renally cleared amino acids, notably serine, led to significant decreases in renal accumulation of less than 20%ID/g 1 hour postinjection (P < 0.05, n = 3). CONCLUSIONS We have engineered highly stable cystine knot peptides with potent and specific integrin α(v)β(6)-binding activities for cancer detection. Pharmacokinetic engineering of scaffold primary sequence led to significant decreases in off-target radiotracer accumulation. Optimization of binding affinity, specificity, stability, and pharmacokinetics will facilitate translation of cystine knots for cancer molecular imaging.
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Affiliation(s)
- Richard H Kimura
- Canary Center for Cancer, Early Detection, Molecular Imaging Program, Department of Radiology, Stanford University School of Medicine, Stanford, California 94305, USA
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Pinto MFS, Almeida RG, Porto WF, Fensterseifer ICM, Lima LA, Dias SC, Franco OL. Cyclotides. J Evid Based Complementary Altern Med 2011. [DOI: 10.1177/2156587211428077] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In recent years, a number of peptides containing a cyclic structural fold have been described. Among them, the cyclotides family was widely reported in different plant tissues, being composed of small cyclic peptides containing 6 conserved cysteine residues connected by disulfide bonds and forming a cysteine-binding cyclic structure known as a cyclic cysteine knot. This structural scaffold is responsible for an enhanced structural stability against chemical, thermal, and proteolytic degradation. Because of the observed stability and multifunctionality, including insecticidal, antimicrobial, and anti-HIV (human immunodeficiency virus) action, much effort has gone into trying to elucidate the structural-function relations of cyclotide compounds. This review focuses on the novelties involving gene structure, precursor formation and processing, and protein folding of the cyclotide family, shedding some light on molecular mechanisms of cyclotide production. Because cyclotides are clear targets for drug development and also biotechnology applications, their chemical synthesis, heterologous systems production, and protein grafting are also addressed.
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Ovesen RG, Brandt KK, Göransson U, Nielsen J, Hansen HCB, Cedergreen N. Biomedicine in the environment: cyclotides constitute potent natural toxins in plants and soil bacteria. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2011; 30:1190-6. [PMID: 21337607 DOI: 10.1002/etc.496] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 11/23/2010] [Accepted: 12/10/2010] [Indexed: 05/07/2023]
Abstract
Bioactive compounds produced by plants are easily transferred to soil and water and may cause adverse ecosystem effects. Cyclotides are gene-encoded, circular, cystine-rich mini-proteins produced in Violaceae and Rubiaceae in high amounts. Based on their biological activity and stability, cyclotides have promising pharmaceutical and agricultural applications. We report the toxicity of the cyclotides: kalata B1, kalata B2, and cycloviolacin O2 extracted from plants to green algae (Pseudokirchneriella subcapitata), duckweed (Lemna minor L.), lettuce (Lactuca sativa L.), and bacteria extracted from soil measured as [³H]leucine incorporation. Quantification by liquid chromatography-mass spectrometry demonstrated up to 98% loss of cyclotides from aqueous solutions because of sorption to test vials. Sorption was prevented by adding bovine serum albumin (BSA) to the aqueous media. Cyclotides were toxic to all test organisms with EC50 values of 12 through 140 µM (algae), 9 through 40 µM (duckweed), 4 through 54 µM (lettuce), and 7 through 26 µM (bacteria). Cycloviolacin O2 was the most potent cyclotide in all assays examined. This report is the first to document toxic effects of cyclotides in plants and soil bacteria and to demonstrate that cyclotides are as toxic as commonly used herbicides and biocides. Hence, cyclotides may adversely affect soil and aquatic environments, which needs to be taken into account in future risk assessment of cropping systems for production of these highly bioactive compounds.
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Affiliation(s)
- Rikke Gleerup Ovesen
- Department of Basic Sciences and Environment, University of Copenhagen, Copenhagen, Denmark.
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Gruber CW, Muttenthaler M, Freissmuth M. Ligand-based peptide design and combinatorial peptide libraries to target G protein-coupled receptors. Curr Pharm Des 2011; 16:3071-88. [PMID: 20687879 DOI: 10.2174/138161210793292474] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 07/21/2010] [Indexed: 01/20/2023]
Abstract
G protein-coupled receptors (GPCRs) are considered to represent the most promising drug targets; it has been repeatedly said that a large fraction of the currently marketed drugs elicit their actions by binding to GPCRs (with cited numbers varying from 30-50%). Closer scrutiny, however, shows that only a modest fraction of (≈60) GPCRs are, in fact, exploited as drug targets, only ≈20 of which are peptide-binding receptors. The vast majority of receptors in the humane genome have not yet been explored as sites of action for drugs. Given the drugability of this receptor class, it appears that opportunities for drug discovery abound. In addition, GPCRs provide for binding sites other than the ligand binding sites (referred to as the "orthosteric site"). These additional sites include (i) binding sites for ligands (referred to as "allosteric ligands") that modulate the affinity and efficacy of orthosteric ligands, (ii) the interaction surface that recruits G proteins and arrestins, (iii) the interaction sites of additional proteins (GIPs, GPCR interacting proteins that regulate G protein signaling or give rise to G protein-independent signals). These sites can also be targeted by peptides. Combinatorial and natural peptide libraries are therefore likely to play a major role in identifying new GPCR ligands at each of these sites. In particular the diverse natural peptide libraries such as the venom peptides from marine cone-snails and plant cyclotides have been established as a rich source of drug leads. High-throughput screening and combinatorial chemistry approaches allow for progressing from these starting points to potential drug candidates. This will be illustrated by focusing on the ligand-based drug design of oxytocin (OT) and vasopressin (AVP) receptor ligands using natural peptide leads as starting points.
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Affiliation(s)
- Christian W Gruber
- Institute of Pharmacology, Center of Biomolecular Medicine & Pharmacology, Medical University of Vienna, Waehringer Str. 13a, A-1090 Vienna, Austria
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Daly NL, Rosengren KJ, Troeira Henriques S, Craik DJ. NMR and protein structure in drug design: application to cyclotides and conotoxins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:359-70. [DOI: 10.1007/s00249-011-0672-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Revised: 12/28/2010] [Accepted: 01/03/2011] [Indexed: 01/14/2023]
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Pranting M, Loov C, Burman R, Goransson U, Andersson DI. The cyclotide cycloviolacin O2 from Viola odorata has potent bactericidal activity against Gram-negative bacteria. J Antimicrob Chemother 2010; 65:1964-71. [DOI: 10.1093/jac/dkq220] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Craik DJ, Mylne JS, Daly NL. Cyclotides: macrocyclic peptides with applications in drug design and agriculture. Cell Mol Life Sci 2010; 67:9-16. [PMID: 19795188 PMCID: PMC11115554 DOI: 10.1007/s00018-009-0159-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 08/20/2009] [Accepted: 09/16/2009] [Indexed: 11/29/2022]
Abstract
Cyclotides are disulfide-rich peptides from plants that are exceptionally stable as a result of their unique cyclic cystine knot structural motif. Their natural role is thought to be as plant defence agents, most notably against insect pests, but they also have potential applications in drug design and agriculture. This article identifies gaps in current knowledge on cyclotides and suggests future directions for research into this fascinating family of ultra-stable mini-proteins.
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Affiliation(s)
- David J Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia.
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Abstract
Cyclotides are plant-derived peptides with a cyclic backbone and knotted topology of disulfide bonds. Their extreme stability and natural sequence variation has led to the suggestion that they might be useful as scaffolds to stabilize bioactive sequences. Recent studies have shown that anti-angiogenic activity and protease inhibitory activity against a foot and mouth disease protease can be grafted onto the cyclotide framework. There has also been significant progress made in determining the mechanism of cyclization of cyclotides and in producing cyclotides using bacterial expression and plant cell culture. There is a wide range of disease states that can be targeted using the cyclotide framework and the advances that have been made in the production of cyclotides will facilitate their development as pharmaceutical templates.
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Craik DJ. Circling the enemy: cyclic proteins in plant defence. TRENDS IN PLANT SCIENCE 2009; 14:328-335. [PMID: 19423383 DOI: 10.1016/j.tplants.2009.03.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 03/06/2009] [Accepted: 03/10/2009] [Indexed: 05/27/2023]
Abstract
Cyclotides are ultra-stable plant proteins that have a circular peptide backbone crosslinked by a cystine knot of disulfide bonds. They are produced in large quantities by plants of the Violaceae and Rubiaceae families and have a role in plant defence against insect predation. As I discuss here, recent studies have begun to reveal how their unique circular topology evolved. Cyclization is achieved by hijacking existing plant proteolytic enzymes and operating them in 'reverse' to form a peptide bond between the N- and C-termini of a linear precursor. Such studies suggest that circular proteins are more common in the plant kingdom than was previously thought, and their exceptional stability has led to their application as protein-engineering templates in drug design.
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Affiliation(s)
- David J Craik
- The University of Queensland, Institute for Molecular Bioscience, Brisbane, QLD 4072, Australia.
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