51
|
He W, Chan LY, Zeng G, Daly NL, Craik DJ, Tan N. Isolation and characterization of cytotoxic cyclotides from Viola philippica. Peptides 2011; 32:1719-23. [PMID: 21723349 DOI: 10.1016/j.peptides.2011.06.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2011] [Revised: 06/16/2011] [Accepted: 06/16/2011] [Indexed: 11/24/2022]
Abstract
Cyclotides are a large family of plant peptides characterized by a macrocyclic backbone and knotted arrangement of three disulfide bonds. This unique structure renders cyclotides exceptionally stable to thermal, chemical and enzymatic treatments. They exhibit a variety of bioactivities, including uterotonic, anti-HIV, cytotoxic and hemolytic activity and it is these properties that make cyclotides an interesting peptide scaffold for drug design. In this study, eight new cyclotides (Viphi A-H), along with eight known cyclotides, were isolated from Viola philippica, a plant from the Violaceae family. In addition, Viba 17 and Mram 8 were isolated for the first time as peptides. The sequences of these cyclotides were elucidated primarily by using a strategy involving reduction, enzymatic digestion and tandem mass spectroscopy sequencing. Several of the cyclotides showed cytotoxic activities against the cancer cell lines MM96L, HeLa and BGC-823. The novel cyclotides reported here: (1) enhance the known sequence variation observed for cyclotides; (2) extend the number of species known to contain cyclotides; (3) provide interesting structure-activity relationships that delineate residues important for cytotoxic activity. In addition, this study provides insights into the potential active ingredients of traditional Chinese medicines.
Collapse
Affiliation(s)
- Wenjun He
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, 132# Lanhei Road, Heilongtan, Kunming 650204, Yunnan, PR China
| | | | | | | | | | | |
Collapse
|
52
|
Ovesen RG, Nielsen J, Hansen HCB. Biomedicine in the environment: sorption of the cyclotide kalata B2 to montmorillonite, goethite, and humic acid. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2011; 30:1785-1792. [PMID: 21590795 DOI: 10.1002/etc.579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 03/22/2011] [Accepted: 04/28/2011] [Indexed: 05/30/2023]
Abstract
Cyclotides are bioactive, stable mini-proteins produced in high amounts in Violaceae and Rubiaceae with promising pharmaceutical and agrochemical applications. Environmental issues must be addressed before large-scale plant cultivation of cyclotides for pharmaceutical or pesticidal purposes can commence. The objective of the present study was to investigate sorption of the cyclotide kalata B2 (kB2), because knowledge of cyclotide biogeochemistry will aid our understanding of environmental fate. The octanol-water partitioning coefficient was determined to be 2.8 ± 0.6 (log K(OW) = 0.4 ± 0.1). Sorption of kB2 by montmorillonite, goethite, and humic acid was investigated at different concentrations and under varying acidity and reached equilibrium within minutes. The kB2 sorption at a solution concentration of 0.2 mg/L to montmorillonite was high (120 mg/g) compared to humic acid (0.60 mg/g) and goethite (0.03 mg/g). Kalata B2 intercalated the interlayer space of montmorillonite. The sorption isotherm for humic acid was linear up to a solution concentration of 0.8 mg/L and concave for montmorillonite and goethite up to an equilibrium solution concentration of 1.5 mg/L. Sorption to goethite was unaffected by pH, but sorption to montmorillonite and humic acid at pH near the isoelectric point (pI) was threefold the sorption when pH > the isoelectric point, suggesting that electrostatic interaction/repulsion between kB2 and sorbents play an important role. The strong sorption to montmorillonite reduces exposure to below toxic threshold values. In addition, the transport risk of soluble cyclotides is reduced, but particle-bound cyclotides may be transported to recipient aquatic sediments with the associated risk of adversely affecting sediment-dwelling organisms.
Collapse
Affiliation(s)
- Rikke Gleerup Ovesen
- University of Copenhagen, Department of Basic Sciences and Environment, Frederiksberg C, Denmark.
| | | | | |
Collapse
|
53
|
Nguyen GKT, Zhang S, Nguyen NTK, Nguyen PQT, Chiu MS, Hardjojo A, Tam JP. Discovery and characterization of novel cyclotides originated from chimeric precursors consisting of albumin-1 chain a and cyclotide domains in the Fabaceae family. J Biol Chem 2011; 286:24275-87. [PMID: 21596752 DOI: 10.1074/jbc.m111.229922] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The tropical plant Clitoria ternatea is a member of the Fabaceae family well known for its medicinal values. Heat extraction of C. ternatea revealed that the bioactive fractions contained heat-stable cysteine-rich peptides (CRPs). The CRP family of A1b (Albumin-1 chain b/leginsulins), which is a linear cystine knot CRP, has been shown to present abundantly in the Fabaceae. In contrast, the cyclotide family, which also belongs to the cystine knot CRPs but with a cyclic structure, is commonly found in the Rubiaceae, Violaceae, and Cucurbitaceae families. In this study, we report the discovery of a panel of 15 heat-stable CRPs, of which 12 sequences (cliotide T1-T12) are novel. We show unambiguously that the cliotides are cyclotides and not A1bs, as determined by their sequence homology, disulfide connectivity, and membrane active properties indicated by their antimicrobial activities against Escherichia coli and cytotoxicities to HeLa cells. We also show that cliotides are prevalent in C. ternatea and are found in every plant tissue examined, including flowers, seeds, and nodules. In addition, we demonstrate that their precursors are chimeras, half from cyclotide and the other half from Albumin-1, with the cyclotide domain displacing the A1b domain in the precursor. Their chimeric structures likely originate from either horizontal gene transfer or convergent evolution in plant nuclear genomes, which are exceedingly rare events. Such atypical genetic arrangement also implies a different mechanism of biosynthetic processing of cyclotides in the Fabaceae and provides new understanding of their evolution in plants.
Collapse
|
54
|
Henriques ST, Huang YH, Rosengren KJ, Franquelim HG, Carvalho FA, Johnson A, Sonza S, Tachedjian G, Castanho MARB, Daly NL, Craik DJ. Decoding the membrane activity of the cyclotide kalata B1: the importance of phosphatidylethanolamine phospholipids and lipid organization on hemolytic and anti-HIV activities. J Biol Chem 2011; 286:24231-41. [PMID: 21576247 DOI: 10.1074/jbc.m111.253393] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Cyclotides, a large family of cyclic peptides from plants, have a broad range of biological activities, including insecticidal, cytotoxic, and anti-HIV activities. In all of these activities, cell membranes seem likely to be the primary target for cyclotides. However, the mechanistic role of lipid membranes in the activity of cyclotides remains unclear. To determine the role of lipid organization in the activity of the prototypic cyclotide, kalata B1 (kB1), and synthetic analogs, their bioactivities and affinities for model membranes were evaluated. We found that the bioactivity of kB1 is dependent on the lipid composition of target cell membranes. In particular, the activity of kB1 requires specific interactions with phospholipids containing phosphatidylethanolamine (PE) headgroups but is further modulated by nonspecific peptide-lipid hydrophobic interactions, which are favored in raft-like membranes. Negatively charged phospholipids do not favor high kB1 affinity. This lipid selectivity explains trends in antimicrobial and hemolytic activities of kB1; it does not target bacterial cell walls, which are negatively charged and lacking PE-phospholipids but can insert in the membranes of red blood cells, which have a low PE content and raft domains in their outer layer. We further show that the anti-HIV activity of kB1 is the result of its ability to target and disrupt the membranes of HIV particles, which are raft-like membranes very rich in PE-phospholipids.
Collapse
Affiliation(s)
- Sónia Troeira Henriques
- University of Queensland, Institute for Molecular Bioscience, Brisbane, Queensland 4072, Australia
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
55
|
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.
Collapse
Affiliation(s)
- Rikke Gleerup Ovesen
- Department of Basic Sciences and Environment, University of Copenhagen, Copenhagen, Denmark.
| | | | | | | | | | | |
Collapse
|
56
|
Wang CKL, Clark RJ, Harvey PJ, Johan Rosengren K, Cemazar M, Craik DJ. The Role of Conserved Glu Residue on Cyclotide Stability and Activity: A Structural and Functional Study of Kalata B12, a Naturally Occurring Glu to Asp Mutant. Biochemistry 2011; 50:4077-86. [DOI: 10.1021/bi2004153] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Conan K. L. Wang
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Richard J. Clark
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Peta J. Harvey
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - K. Johan Rosengren
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Masa Cemazar
- 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
| |
Collapse
|
57
|
Abstract
Cyclotides are disulfide-rich miniproteins with a circular backbone and a knotted arrangement ofdisulfide bonds. Because these plant-derived peptides are resistant to degradation and exhibit a diverse range of bioactivity they have become important agronomic and industrial objectives. They belong to a group of compounds with low market volume and high price that are poorly processed by microorganisms, are too complex for economic chemical synthesis, and thus are valuable candidates for the synthesis in plant cell bioprocesses. This review highlights current research aimed at production routes of cyclotides in Oldenlandia affinis plantlets and cell cultures, and summarizes recent advances in bioprocessing aspects, with particular emphasis on the development of suitable bioreactor configurations for plant cell culture-based processes, the optimization of culture environments as a powerful means to improve yields, bioreactor operational modes, and trends in protein recovery.
Collapse
Affiliation(s)
- Heike Dörnenburg
- Institute of Bioprocess Engineering, University of Erlangen-Nuremberg, Paul-Gordan-Str. 3, 91052 Erlangen, Germany.
| |
Collapse
|
58
|
Abstract
In recent years, the discovery of a large family of macrocyclic peptides, the cyclotides, has revealed Natures ingenuity in molecular drug design. The incorporation of a cyclic peptide backbone and a knotted arrangement of disulfide bridges into their structures confers extraordinary chemical, thermal, and enzymatic stability on these biologically active peptides. However, these structural attributes present challenges in the identification of cyclotides. Until now, the sequencing of cyclotides has been slow and inefficient owing to inherent difficulties in the separation of these hydrophobic peptides from plants, the multiple chemical and enzymatic derivatization steps required to make them amenable to mass spectrometric sequencing, and the lack of software tools to efficiently deal with these circular permutants. The current bottleneck slowing the speed of cyclotide sequencing is the requirement for multiple HPLC purification steps before analysis. Here, we have applied proteomic strategies to fast-track the discovery of known, modified and novel sequences. Using four fractions from a previously well-characterized cyclotide-containing plant species, Viola odorata, 11 new sequences, as well as a plethora of known and modified cyclotides, were uncovered. In addition, the methodology was validated through analysis of crude leaf extracts ofOldenlandia affinis and Arabidopsis thaliana. The unambiguous identification of a suite of cyclotides in the Oldenlandia affinis extract provided the ultimate proof-of-concept for this application. Major advances in methodology include the use of optimized LC-MS/MS conditions and design of a custom-built cyclotide database, in which mature cyclotide sequences are excised, replicated and appended, marking a new "era" for cyclotide sequencing.
Collapse
|
59
|
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.
Collapse
Affiliation(s)
- Christian W Gruber
- Institute of Pharmacology, Center of Biomolecular Medicine & Pharmacology, Medical University of Vienna, Waehringer Str. 13a, A-1090 Vienna, Austria
| | | | | |
Collapse
|
60
|
Aboye TL, Clark RJ, Burman R, Roig MB, Craik DJ, Göransson U. Interlocking disulfides in circular proteins: toward efficient oxidative folding of cyclotides. Antioxid Redox Signal 2011; 14:77-86. [PMID: 20486762 DOI: 10.1089/ars.2010.3112] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cyclotides are ultrastable plant proteins characterized by the presence of a cyclic amide backbone and three disulfide bonds that form a cystine knot. Because of their extreme stability, there has been significant interest in developing these molecules as a drug design scaffold. For this potential to be realized, efficient methods for the synthesis and oxidative folding of cyclotides need to be developed, yet we currently have only a basic understanding of the folding mechanism and the factors influencing this process. In this study, we determine the major factors influencing oxidative folding of the different subfamilies of cyclotides. The folding of all the cyclotides examined was heavily influenced by the concentration of redox reagents, with the folding rate and final yield of the native isomer greatly enhanced by high concentrations of oxidized glutathione. Addition of hydrophobic solvents to the buffer also enhanced the folding rates and appeared to alter the folding pathway. Significant deamidation and isoaspartate formation were seen when oxidation conditions were conducive to slow folding. The identification of factors that influence the folding and degradation pathways of cyclotides will facilitate the development of folding screens and optimized conditions for producing cyclotides and grafted analogs as stable peptide-based therapeutics.
Collapse
Affiliation(s)
- Teshome Leta Aboye
- Division of Pharmacognosy, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, Uppsala, Sweden
| | | | | | | | | | | |
Collapse
|
61
|
Burman R, Herrmann A, Tran R, Kivelä JE, Lomize A, Gullbo J, Göransson U. Cytotoxic potency of small macrocyclic knot proteins: Structure–activity and mechanistic studies of native and chemically modified cyclotides. Org Biomol Chem 2011; 9:4306-14. [DOI: 10.1039/c0ob00966k] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
62
|
Discovery and applications of the plant cyclotides. Toxicon 2010; 56:1092-102. [DOI: 10.1016/j.toxicon.2010.02.021] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 02/02/2010] [Accepted: 02/18/2010] [Indexed: 11/20/2022]
|
63
|
Ireland DC, Clark RJ, Daly NL, Craik DJ. Isolation, sequencing, and structure-activity relationships of cyclotides. JOURNAL OF NATURAL PRODUCTS 2010; 73:1610-1622. [PMID: 20718473 DOI: 10.1021/np1000413] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Cyclotides are a topologically fascinating family of miniproteins discovered over the past decade that have expanded the diversity of plant-derived natural products. They are approximately 30 amino acids in size and occur in plants of the Violaceae, Rubiaceae, and Cucurbitaceae families. Despite their proteinaceous composition, cyclotides behave in much the same way as many nonpeptidic natural products in that they are resistant to degradation by enzymes or heat and can be extracted from plants using methanol. Their stability arises, in large part, due to their characteristic cyclic cystine knot (CCK) structural motif. Cystine knots are present in a variety of proteins of insect, plant, and animal origin, comprising a ring formed by two disulfide bonds and their connecting backbone segments that is threaded by a third disulfide bond. In cyclotides, the cystine knot is uniquely embedded within a head-to-tail cyclized peptide backbone, leading to the ultrastable CCK structural motif. Apart from the six absolutely conserved cysteine residues, the majority of amino acids in the six backbone loops of cyclotides are tolerant to variation. It has been predicted that the family might include up to 50,000 members; although, so far, sequences for only 140 have been reported. Cyclotides exhibit a variety of biological activities, including insecticidal, nematocidal, molluscicidal, antimicrobial, antibarnacle, anti-HIV, and antitumor activities. Due to their diverse activities and common structural core from which variable loops protrude, cyclotides can be thought of as combinatorial peptide templates capable of displaying a variety of amino acid sequences. They have thus attracted interest in drug design as well as in crop protection applications.
Collapse
Affiliation(s)
- David C Ireland
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | | | | |
Collapse
|
64
|
Tang J, Wang CK, Pan X, Yan H, Zeng G, Xu W, He W, Daly NL, Craik DJ, Tan N. Isolation and characterization of cytotoxic cyclotides from Viola tricolor. Peptides 2010; 31:1434-40. [PMID: 20580652 DOI: 10.1016/j.peptides.2010.05.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 05/10/2010] [Accepted: 05/10/2010] [Indexed: 11/27/2022]
Abstract
Many plants of the Violaceae plant family have been used in traditional remedies, and these plants often contain cyclotides, a particular type of plant cyclopeptide that is distinguished by a cyclic cystine knot motif. In general, bioactive plant cyclopeptides are interesting candidates for drug development. In the current study, a suite of 14 cyclotides, which includes seven novel cyclotides [vitri B, C, D, E, F, varv Hm, and He], together with seven known cyclotides [varv A, D, E, F, H, vitri A, and cycloviolacin O2], was isolated from Viola tricolor, a common flower. A chromatography-based method was used to isolate the cyclotides, which were characterized using tandem mass spectrometry and NMR spectroscopy. Several of the cyclotides showed cytotoxic activities against five cancer cell lines, U251, MDA-MB-231, A549, DU145, and BEL-7402. Three cyclotides, vitri A, vitri F, and cycloviolacin O2, were the most cytotoxic. The cytotoxic activity of the cyclotides did not correlate well with their hemolytic activity, indicating that different interactions, most likely with membranes, are involved for cytotoxic and hemolytic activities. Homology modeling of the structures was used in deriving structure-activity relationships.
Collapse
Affiliation(s)
- Jun Tang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, 132# Lanhei Road, Heilongtan, Kunming 650204, Yunnan, PR China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
65
|
Gerlach SL, Burman R, Bohlin L, Mondal D, Göransson U. Isolation, characterization, and bioactivity of cyclotides from the Micronesian plant Psychotria leptothyrsa. JOURNAL OF NATURAL PRODUCTS 2010; 73:1207-1213. [PMID: 20575512 DOI: 10.1021/np9007365] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Cyclotides, the largest known family of head-to-tail cyclic peptides, have approximately 30 amino acid residues with a complex structure containing a circular peptide backbone and a cystine knot. They are found in plants from the Violaceae and Rubiaceae families and are speculated to function in plant protection. In addition to their insecticidal properties, cyclotides display cytotoxic, anti-HIV, antimicrobial, and inhibition of neurotensin binding activities. Although cyclotides are present in all violaceous species hitherto screened, their distribution and expression in Rubiaceae are not fully understood. In this study, we show that Psychotria leptothyrsa var. longicarpa (Rubiaceae) contains a suite of different cyclotides. The cyclotide fractions were isolated by RP-HPLC, and sequences of six new peptides, named psyles A-F, were determined by MS/MS sequencing. One of these, psyle C, is the first rubiaceous linear variant known. Psyles A, C, and E were analyzed in a fluorometric microculture assay to determine cytotoxicity toward the human lymphoma cell line U937-GTB. The IC(50) values of psyles A, C, and E were 26, 3.50, and 0.76 muM, respectively. This study expands the number of known rubiaceous cyclotides and shows that the linear cyclotide maintains cytotoxicity.
Collapse
Affiliation(s)
- Samantha L Gerlach
- Department of Ecology and Evolutionary Biology, Tulane University, 6823 St. Charles Avenue, New Orleans, LA 70118, USA.
| | | | | | | | | |
Collapse
|
66
|
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
|
67
|
Mylne JS, Wang CK, van der Weerden NL, Craik DJ. Cyclotides are a component of the innate defense of Oldenlandia affinis. Biopolymers 2010; 94:635-46. [DOI: 10.1002/bip.21419] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
68
|
Kaas Q, Craik DJ. Analysis and classification of circular proteins in CyBase. Biopolymers 2010; 94:584-91. [DOI: 10.1002/bip.21424] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
69
|
Plan MR, Rosengren KJ, Sando L, Daly NL, Craik DJ. Structural and biochemical characteristics of the cyclotide kalata B5 from Oldenlandia affinis. Biopolymers 2010; 94:647-58. [DOI: 10.1002/bip.21409] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
70
|
Qin Q, McCallum EJ, Kaas Q, Suda J, Saska I, Craik DJ, Mylne JS. Identification of candidates for cyclotide biosynthesis and cyclisation by expressed sequence tag analysis of Oldenlandia affinis. BMC Genomics 2010; 11:111. [PMID: 20158917 PMCID: PMC2838841 DOI: 10.1186/1471-2164-11-111] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 02/16/2010] [Indexed: 11/15/2022] Open
Abstract
Background Cyclotides are a family of circular peptides that exhibit a range of biological activities, including anti-bacterial, cytotoxic, anti-HIV activities, and are proposed to function in plant defence. Their high stability has motivated their development as scaffolds for the stabilisation of peptide drugs. Oldenlandia affinis is a member of the Rubiaceae (coffee) family from which 18 cyclotides have been sequenced to date, but the details of their processing from precursor proteins have only begun to be elucidated. To increase the speed at which genes involved in cyclotide biosynthesis and processing are being discovered, an expressed sequence tag (EST) project was initiated to survey the transcript profile of O. affinis and to propose some future directions of research on in vivo protein cyclisation. Results Using flow cytometry the holoploid genome size (1C-value) of O. affinis was estimated to be 4,210 - 4,284 Mbp, one of the largest genomes of the Rubiaceae family. High-quality ESTs were identified, 1,117 in total, from leaf cDNAs and assembled into 502 contigs, comprising 202 consensus sequences and 300 singletons. ESTs encoding the cyclotide precursors for kalata B1 (Oak1) and kalata B2 (Oak4) were among the 20 most abundant ESTs. In total, 31 ESTs encoded cyclotide precursors, representing a distinct commitment of 2.8% of the O. affinis transcriptome to cyclotide biosynthesis. The high expression levels of cyclotide precursor transcripts are consistent with the abundance of mature cyclic peptides in O. affinis. A new cyclotide precursor named Oak5 was isolated and represents the first cDNA for the bracelet class of cyclotides in O. affinis. Clones encoding enzymes potentially involved in processing cyclotides were also identified and include enzymes involved in oxidative folding and proteolytic processing. Conclusion The EST library generated in this study provides a valuable resource for the study of the cyclisation of plant peptides. Further analysis of the candidates for cyclotide processing discovered in this work will increase our understanding and aid in reconstructing cyclotide production using transgenic systems and will benefit their development in pharmaceutical applications and insect-resistant crop plants.
Collapse
Affiliation(s)
- Qiaoping Qin
- The University of Queensland, Institute for Molecular Bioscience, Brisbane, Queensland, 4072, Australia
| | | | | | | | | | | | | |
Collapse
|
71
|
Göransson U, Herrmann A, Burman R, Haugaard-Jönsson LM, Rosengren KJ. The conserved glu in the cyclotide cycloviolacin O2 has a key structural role. Chembiochem 2010; 10:2354-60. [PMID: 19735083 DOI: 10.1002/cbic.200900342] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cyclotides are a large family of plant peptides that are characterised by a head-to-tail circular backbone and three disulfide bonds that are arranged in a cystine knot. This unique structural feature, which is referred to as a cyclic cystine knot, gives the cyclotides remarkable stability against chemical and biological degradation. In addition to their natural function as insecticides for plant defence, the cyclotides have a range of bioactivities with pharmaceutical relevance, including cytotoxicity against cancer cell lines. A glutamic acid residue, aside from the invariable disulfide array, is the most conserved feature throughout the cyclotide family, and it has recently been shown to be crucial for biological activity. Here we have used solution-state NMR spectroscopy to determine the three-dimensional structures of the potent cytotoxic cyclotide cycloviolacin O2, and an inactive analogue in which this conserved glutamic acid has been methylated. The structures of the peptides show that the glutamic acid has a key structural role in coordinating a set of hydrogen bonds in native cycloviolacin O2; this interaction is disrupted in the methylated analogue. The proposed mechanism of action of cyclotides is membrane disruption and these results suggest that the glutamic acid is linked to cyclotide function by stabilising the structure to allow efficient aggregation in membranes, rather than in a direct interaction with a target receptor.
Collapse
Affiliation(s)
- Ulf Göransson
- Division of Pharmacognosy, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, 751 23 Uppsala, Sweden
| | | | | | | | | |
Collapse
|
72
|
Daly NL, Chen B, Nguyencong P, Craik DJ. Structure and Activity of the Leaf-Specific Cyclotide vhl-2. Aust J Chem 2010. [DOI: 10.1071/ch10007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Cyclotides are plant-derived macrocyclic peptides with potential applications in the pharmaceutical and agricultural industries. In addition to their presumed natural function as host-defence peptides arising from their insecticidal activity, their other biological activities include antimicrobial, haemolytic, and cytotoxic activities, but at present, only limited information is available on the structural and chemical features that are important for these various activities. In the current study, we determined the three-dimensional structure of vhl-2, a leaf-specific cyclotide. Although the characteristic cyclic cystine knot fold of other cyclotides is maintained in vhl-2, it has more potent haemolytic activity than well-characterized cyclotides such as kalata B1 and kalata B8. Analysis of surface hydrophobicity and haemolytic activity for a range of cyclotides indicates a correlation between them, with increasing hydrophobicity resulting in increased haemolytic activity. This correlation is consistent with membrane binding being a vital step in mediating the various cytotoxic activities of cyclotides. The gene sequence for vhl-2 was determined and indicates that vhl-2 is processed from a multidomain precursor protein that also encodes the cyclotide cycloviolacin H3.
Collapse
|
73
|
Wang CK, Colgrave ML, Ireland DC, Kaas Q, Craik DJ. Despite a conserved cystine knot motif, different cyclotides have different membrane binding modes. Biophys J 2009; 97:1471-81. [PMID: 19720036 DOI: 10.1016/j.bpj.2009.06.032] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 06/03/2009] [Accepted: 06/10/2009] [Indexed: 11/19/2022] Open
Abstract
Cyclotides are cyclic proteins produced by plants for defense against pests. Because of their remarkable stability and diverse bioactivities, they have a range of potential therapeutic applications. The bioactivities of cyclotides are believed to be mediated through membrane interactions. To determine the structural basis for the biological activity of the two major subfamilies of cyclotides, we determined the conformation and orientation of kalata B2 (kB2), a Möbius cyclotide, and cycloviolacin O2 (cO2), a bracelet cyclotide, bound to dodecylphosphocholine micelles, using NMR spectroscopy in the presence and absence of 5- and 16-doxylstearate relaxation probes. Analysis of binding curves using the Langmuir isotherm indicated that cO2 and kB2 have association constants of 7.0 x 10(3) M(-1) and 6.0 x 10(3) M(-1), respectively, consistent with the notion that they are bound near the surface, rather than buried deeply within the micelle. This suggestion is supported by the selective broadening of micelle-bound cyclotide NMR signals upon addition of paramagnetic Mn ions. The cyclotides from the different subfamilies exhibited clearly different binding orientations at the micelle surface. Structural analysis of cO2 confirmed that the main element of the secondary structure is a beta-hairpin centered in loop 5. A small helical turn is present in loop 3. Analysis of the surface profile of cO2 shows that a hydrophobic patch stretches over loops 2 and 3, in contrast to the hydrophobic patch of kB2, which predominantly involves loops 2 and 5. The different location of the hydrophobic patches in the two cyclotides explains their different binding orientations and provides an insight into the biological activities of cyclotides.
Collapse
Affiliation(s)
- Conan K Wang
- University of Queensland, Institute for Molecular Bioscience, Brisbane, Queensland, Australia
| | | | | | | | | |
Collapse
|
74
|
Huang YH, Colgrave ML, Daly NL, Keleshian A, Martinac B, Craik DJ. The biological activity of the prototypic cyclotide kalata b1 is modulated by the formation of multimeric pores. J Biol Chem 2009; 284:20699-707. [PMID: 19491108 DOI: 10.1074/jbc.m109.003384] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cyclotides are a large family of circular mini-proteins containing a cystine knot motif. They are expressed in plants as defense-related proteins, with insecticidal activity. Here we investigate their role in membrane interaction and disruption. Kalata B1, a prototypic cyclotide, was found to induce leakage of the self-quenching fluorophore, carboxyfluorescein, from phospholipid vesicles. Alanine-scanning mutagenesis of kalata B1 showed that residues essential for lytic activity are clustered, forming a bioactive face. Kalata B1 was sequestered at the membrane surface and showed slow dissociation from vesicles. Electrophysiological experiments showed that conductive pores were induced in liposome patches on incubation with kalata B1. The conductance calculated from the current-voltage relationship indicated that the diameter of the pores formed in the bilayer patches is 41-47 A. Collectively, the findings provide a mechanistic explanation for the diversity of biological functions ascribed to this fascinating family of ultrastable macrocyclic peptides.
Collapse
Affiliation(s)
- Yen-Hua Huang
- Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia
| | | | | | | | | | | |
Collapse
|
75
|
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.
Collapse
Affiliation(s)
- David J Craik
- The University of Queensland, Institute for Molecular Bioscience, Brisbane, QLD 4072, Australia.
| |
Collapse
|
76
|
Trabi M, Mylne JS, Sando L, Craik DJ. Circular proteins from Melicytus (Violaceae) refine the conserved protein and gene architecture of cyclotides. Org Biomol Chem 2009; 7:2378-88. [PMID: 19462049 DOI: 10.1039/b823020j] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclotides are cyclic disulfide rich mini-proteins found in various Rubiaceae (coffee family), Violaceae (violet family) and Cucurbitaceae (squash family) plant species. Within the Violaceae, cyclotides have been found in numerous species of the genus Viola as well as species from two other genera, namely Hybanthus and Leonia. This is the first in-depth report of cyclotides in the genus Melicytus (Violaceae). We present the chromatographic profiles of extracts of eight Melicytus species and one Melicytus hybrid that were found to contain these circular peptides. We isolated and characterised five novel cyclotides (mra1 to mra5) from the aerial parts of a common New Zealand tree, Melicytus ramiflorus. All five peptides show the characteristics of the bracelet subfamily of cyclotides. Furthermore, we isolated 17 non-redundant cDNA clones from the leaves of Melicytus ramiflorus encoding cyclotide prepropeptides. This detailed report on the presence of cyclotides in several species of the genus Melicytus further strengthens our hypothesis that cyclotides are ubiquitous in Violaceae family plants and provides additional insight into the biochemical processing mechanisms that produce the cyclic protein backbone of this unique family of ultra-stable plant proteins.
Collapse
Affiliation(s)
- Manuela Trabi
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
| | | | | | | |
Collapse
|
77
|
Abstract
Cyclotides are 28-37 amino acid peptides incorporating three disulfide bonds and a cyclic backbone. Their cyclic and knotted topology renders them immune to denaturation by heat or organic solvents and highly resistant to proteolysis. They have a range of interesting and potentially useful pharmaceutical properties and have been proposed as scaffolds within which peptides with drug activities can be stabilized for delivery. Some members of the family also have agricultural applications deriving from their potent insecticidal activity. Labeling peptides with the NMR-active and stable 15N isotope facilitates a range of studies by NMR, including structural and dynamics studies and their use as tracers. However, owing to their head-to-tail cyclized peptide backbone labeled cyclotides are not amenable to conventional recombinant labeling strategies. We have developed an approach to overcome this limitation by growing the cyclotide-bearing plant Oldenlandia affinis on nitrogen-free agar media supplemented with 15N salts and obtaining complete labeling at no detriment to plant biomass. We purified the insecticidal cyclotides kalata B1 and kalata B2 as examples and provide heteronuclear single quantum coherence (HSQC) NMR spectra for each. This method of labeling cyclotides involves only a fraction of the cost of uniform labeling by solid-phase peptide synthesis.
Collapse
Affiliation(s)
- Joshua S Mylne
- Division of Chemical and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072, Australia
| | | |
Collapse
|
78
|
Gruber CW, Elliott AG, Ireland DC, Delprete PG, Dessein S, Göransson U, Trabi M, Wang CK, Kinghorn AB, Robbrecht E, Craik DJ. Distribution and evolution of circular miniproteins in flowering plants. THE PLANT CELL 2008; 20:2471-83. [PMID: 18827180 PMCID: PMC2570719 DOI: 10.1105/tpc.108.062331] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cyclotides are disulfide-rich miniproteins with the unique structural features of a circular backbone and knotted arrangement of three conserved disulfide bonds. Cyclotides have been found only in two plant families: in every analyzed species of the violet family (Violaceae) and in few species of the coffee family (Rubiaceae). In this study, we analyzed >200 Rubiaceae species and confirmed the presence of cyclotides in 22 species. Additionally, we analyzed >140 species in related plant families to Rubiaceae and Violaceae and report the occurrence of cyclotides in the Apocynaceae. We further report new cyclotide sequences that provide insights into the mechanistic basis of cyclotide evolution. On the basis of the phylogeny of cyclotide-bearing plants and the analysis of cyclotide precursor gene sequences, we hypothesize that cyclotide evolution occurred independently in various plant families after the divergence of Asterids and Rosids ( approximately 125 million years ago). This is strongly supported by recent findings on the in planta biosynthesis of cyclotides, which involves the serendipitous recruitment of ubiquitous proteolytic enzymes for cyclization. We further predict that the number of cyclotides within the Rubiaceae may exceed tens of thousands, potentially making cyclotides one of the largest protein families in the plant kingdom.
Collapse
Affiliation(s)
- Christian W Gruber
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
79
|
Saska I, Colgrave ML, Jones A, Anderson MA, Craik DJ. Quantitative analysis of backbone-cyclised peptides in plants. J Chromatogr B Analyt Technol Biomed Life Sci 2008; 872:107-14. [PMID: 18701356 DOI: 10.1016/j.jchromb.2008.07.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 07/08/2008] [Accepted: 07/17/2008] [Indexed: 01/23/2023]
Abstract
Progress in understanding the biosynthetic pathway of the cyclotides has been hampered as this unique family of cyclic plant peptides are notoriously difficult to analyse by standard proteomic approaches such as gel electrophoresis. We have developed a simple, rapid and robust strategy for the quantification of cyclotides in crude plant extracts using MALDI-TOF MS making use of generic peptides similar in mass to the analyte as internal standards for calibration. Linearity (r(2)>0.99) over two orders of magnitude (down to femtomole levels) was achieved in plant extracts, allowing quantitative analysis of transgenic and endogenous peptide expression.
Collapse
Affiliation(s)
- Ivana Saska
- Institute for Molecular Bioscience, University of Queensland, 306 Carmody Road, Brisbane, Queensland 4072, Australia
| | | | | | | | | |
Collapse
|
80
|
Plan MRR, Saska I, Cagauan AG, Craik DJ. Backbone cyclised peptides from plants show molluscicidal activity against the rice pest Pomacea canaliculata (golden apple snail). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2008; 56:5237-41. [PMID: 18557620 DOI: 10.1021/jf800302f] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Golden apple snails ( Pomacea canaliculata) are serious pests of rice in South East Asia. Cyclotides are backbone cyclized peptides produced by plants from Rubiaceae and Violaceae. In this study, we investigated the molluscicidal activity of cyclotides against golden apple snails. Crude cyclotide extracts from both Oldenlandia affinis and Viola odorata plants showed molluscicidal activity comparable to the synthetic molluscicide metaldehyde. Individual cyclotides from each extract demonstrated a range of molluscicidal activities. The cyclotides cycloviolacin O1, kalata B1, and kalata B2 were more toxic to golden apple snails than metaldehyde, while kalata B7 and kalata B8 did not cause significant mortality. The toxicity of the cyclotide kalata B2 on a nontarget species, the Nile tilapia ( Oreochromis niloticus), was three times lower than the common piscicide rotenone. Our findings suggest that the existing diversity of cyclotides in plants could be used to develop natural molluscicides.
Collapse
Affiliation(s)
- Manuel Rey R Plan
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | | | | | | |
Collapse
|
81
|
Simonsen SM, Sando L, Rosengren KJ, Wang CK, Colgrave ML, Daly NL, Craik DJ. Alanine scanning mutagenesis of the prototypic cyclotide reveals a cluster of residues essential for bioactivity. J Biol Chem 2008; 283:9805-13. [PMID: 18258598 DOI: 10.1074/jbc.m709303200] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cyclotides are stable plant-derived mini-proteins with a topologically circular peptide backbone and a knotted arrangement of three disulfide bonds that form a cyclic cystine knot structural framework. They display a wide range of pharmaceutically important bioactivities, but their natural function is in plant defense as insecticidal agents. To determine the influence of individual residues on structure and activity in the prototypic cyclotide kalata B1, all 23 non-cysteine residues were successively replaced with alanine. The structure was generally tolerant of modification, indicating that the framework is a viable candidate for the stabilization of bioactive peptide epitopes. Remarkably, insecticidal and hemolytic activities were both dependent on a common, well defined cluster of hydrophilic residues on one face of the cyclotide. Interestingly, this cluster is separate from the membrane binding face of the cyclotides. Overall, the mutagenesis data provide an important insight into cyclotide biological activity and suggest that specific self-association, in combination with membrane binding mediates cyclotide bioactivities.
Collapse
Affiliation(s)
- Shane M Simonsen
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia
| | | | | | | | | | | | | |
Collapse
|
82
|
Herrmann A, Burman R, Mylne JS, Karlsson G, Gullbo J, Craik DJ, Clark RJ, Göransson U. The alpine violet, Viola biflora, is a rich source of cyclotides with potent cytotoxicity. PHYTOCHEMISTRY 2008; 69:939-52. [PMID: 18191970 DOI: 10.1016/j.phytochem.2007.10.023] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 10/15/2007] [Accepted: 10/16/2007] [Indexed: 05/02/2023]
Abstract
The cyclotides are currently the largest known family of head-to-tail cyclic proteins. The complex structure of these small plant proteins, which consist of approximately 30 amino acid residues, contains both a circular peptide backbone and a cystine knot, the combination of which produces the cyclic cystine knot motif. To date, cyclotides have been found in plants from the Rubiaceae, Violaceace and Cucurbitaceae families, and are believed to be part of the host defence system. In addition to their insecticidal effect, cyclotides have also been shown to be cytotoxic, anti-HIV, antimicrobial and haemolytic agents. In this study, we show that the alpine violet Viola biflora (Violaceae) is a rich source of cyclotides. The sequences of 11 cyclotides, vibi A-K, were determined by isolation and MS/MS sequencing of proteins and screening of a cDNA library of V. biflora in parallel. For the cDNA screening, a degenerate primer against a conserved (AAFALPA) motif in the cyclotide precursor ER signal sequence yielded a series of predicted cyclotide sequences that were correlated to those of the isolated proteins. There was an apparent discrepancy between the results of the two strategies as only one of the isolated proteins could be identified as a cDNA clone. Finally, to correlate amino acid sequence to cytotoxic potency, vibi D, E, G and H were analysed using a fluorometric microculture cytotoxicity assay using a lymphoma cell line. The IC(50)-values of the bracelet cyclotides vibi E, G and H ranged between 0.96 and 5.0 microM while the Möbius cyclotide vibi D was not cytotoxic at 30 microM.
Collapse
Affiliation(s)
- Anders Herrmann
- Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Centre, P.O. Box 574, SE-751 23 Uppsala, Sweden
| | | | | | | | | | | | | | | |
Collapse
|
83
|
Shenkarev ZO, Nadezhdin KD, Lyukmanova EN, Sobol VA, Skjeldal L, Arseniev AS. Divalent cation coordination and mode of membrane interaction in cyclotides: NMR spatial structure of ternary complex Kalata B7/Mn2+/DPC micelle. J Inorg Biochem 2008; 102:1246-56. [PMID: 18295894 DOI: 10.1016/j.jinorgbio.2008.01.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 12/15/2007] [Accepted: 01/10/2008] [Indexed: 10/22/2022]
Abstract
The cyclotides are the family of hydrophobic bioactive plant peptides, characterized by a circular protein backbone and three knot forming disulfide bonds. It is believed that membrane activity of the cyclotides underlines their antimicrobial, cytotoxic and hemolytic properties, but the specific interactions with divalent cations can be also involved. To assess the mode of membrane interaction and divalent cation coordination in cyclotides, the spatial structure of the Möbius cyclotide Kalata B7 from the African perennial plant Oldenlandia affinis was determined in the presence of anisotropic membrane mimetic (dodecylphosphocholine micelles). The model of peptide/cation/micelle complex was built using 5-doxylstearate and Mn2+ relaxation probes. Results show that the peptide binds to the micelle surface with relatively high affinity by two hydrophobic loops (loop 2 - Thr6-Leu7 and loop 5 - Trp19-Ile21). The partially hydrated divalent cation is coordinated by charged side-chain of Glu3, aromatic side chain of Tyr11 and free carbonyls of Thr4 and Thr9, and is located in direct contact with the polar head-groups of detergent. The comparison with data about other cyclotides indicates that divalent cation coordination is the invariant property of all cyclotides, but the mode of peptide/membrane interactions is varied. Probably, the specific cation/peptide interactions play a major, but yet not known, role in the biological activity of the cyclotides.
Collapse
Affiliation(s)
- Zakhar O Shenkarev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Str. 16/10, 117997 Moscow, Russia
| | | | | | | | | | | |
Collapse
|
84
|
Microwave-assisted Boc-solid phase peptide synthesis of cyclic cysteine-rich peptides. J Pept Sci 2008; 14:683-9. [DOI: 10.1002/psc.972] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
85
|
Wang CKL, Colgrave ML, Gustafson KR, Ireland DC, Goransson U, Craik DJ. Anti-HIV cyclotides from the Chinese medicinal herb Viola yedoensis. JOURNAL OF NATURAL PRODUCTS 2008; 71:47-52. [PMID: 18081258 PMCID: PMC6327322 DOI: 10.1021/np070393g] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Cyclotides are macrocyclic plant peptides characterized by a knotted arrangement of three disulfide bonds. They display a range of interesting bioactivities, including anti-HIV and insecticidal activities. More than 100 different cyclotides have been isolated from two phylogenetically distant plant families, the Rubiaceae and Violaceae. In this study we have characterized the cyclotides from Viola yedoensis, an important Chinese herb from the Violaceae family that has been reported to contain potential anti-HIV agents. From V. yedoensis five new and three known cyclotides were identified and shown to have anti-HIV activity. The most active of these is cycloviolacin Y5, which is one of the most potent of all cyclotides tested so far using in vitro XTT-based anti-HIV assays. Cycloviolacin Y5 is the most hydrophobic of the cyclotides from V. yedoensis. We show that there is a positive correlation between the hydrophobicity and the anti-HIV activity of the new cyclotides and that this trend tracks with their ability to disrupt membranes, as judged from hemolytic assays on human erythrocytes.
Collapse
Affiliation(s)
| | | | | | | | | | - David J. Craik
- To whom correspondence should be addressed. Tel: 61-7-3346-2019. Fax: 61-7-3346-2029.
| |
Collapse
|
86
|
Seydel P, Gruber CW, Craik DJ, Dörnenburg H. Formation of cyclotides and variations in cyclotide expression in Oldenlandia affinis suspension cultures. Appl Microbiol Biotechnol 2007; 77:275-84. [PMID: 17786427 DOI: 10.1007/s00253-007-1159-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 08/06/2007] [Accepted: 08/06/2007] [Indexed: 10/22/2022]
Abstract
Cyclotides, a family of disulfide-rich mini-proteins, show a wide range of biological activities, making them interesting targets for pharmaceutical and agrochemical applications, but little is known about their natural function and the events that trigger their expression. An investigation of nutritional variations and irradiation during a batch process involving plant cell cultures has been performed, using the native African medical herb, Oldenlandia affinis, as a model plant. The results demonstrated the biosynthesis of kalata B1, the main cyclotide in O. affinis, in a combined growth/nongrowth-associated pattern. The highest concentration, 0.37 mg g(-1) dry weight, was accumulated in irradiated cells at 35 mumol m(-2) s(-1). Furthermore, 12 novel cyclotides were identified and the expression of various cyclotides compared in irradiated vs non-irradiated cultures. The results indicate that cyclotide expression varies greatly depending on physiological conditions and environmental stress. Kalata B1 is the most abundant cyclotide in plant suspension cultures, which underlies its importance as a natural defense molecule. The identification of novel cyclotides in suspension cultures, compared to whole plants, indicates that there may be more novel cyclotides to be discovered and that the genetic network regulating cyclotide expression is a very sensitive system, ready to adapt to the current environmental growth condition.
Collapse
Affiliation(s)
- Peter Seydel
- Institute of Bioprocess Engineering, University of Erlangen-Nuremberg, 91052, Erlangen, Germany
| | | | | | | |
Collapse
|