A mitogenic defensin from white cloud beans (Phaseolus vulgaris)

Chickpea Peptide: A Nutraceutical Molecule Corroborating Neurodegenerative and ACE-I Inhibition

Chickpea seeds are the source of proteins in human nutrition and attribute some nutraceutical properties. Herein, we report the effects of chickpea seed bioactive peptide on albumin, insulin, lactoglobulin and lysozyme amyloid fibril formation. Employing thioflavin T (ThT) assays and circular dichroism (CD), amyloid structural binding transition was experimented to analyze the inhibition of amyloid fibril formation. The purified active peptide with a molecular mass of 934.53 Da was evaluated in vitro for its ACE-I inhibitory, antibacterial, antifungal and antidiabetic activities. Further, in vivo animal studies were carried out in wistar rats for blood pressure lowering action. In hypertensive rats, chickpea peptide decreased 131 ± 3.57 mm of Hg for systolic blood pressure and 86 ± 1.5 mm of Hg for diastolic blood pressure after 8 h intraperitoneal administration. Additionally, the peptide suppressed the fibrillation of amyloid and destabilized the preformed mature fibrils. Data emphasize efficacy of chickpea peptide vis-a-vis ACE-Inhibitory, antibacterial, antifungal, antidiabetic and anti-amyloidogenic activities, allowing us to propose this novel peptide as a suitable candidate for nutraceutical-based drugs and seems the first kind of its nature.

Use of Defensins to Develop Eco-Friendly Alternatives to Synthetic Fungicides to Control Phytopathogenic Fungi and Their Mycotoxins

Crops are threatened by numerous fungal diseases that can adversely affect the availability and quality of agricultural commodities. In addition, some of these fungal phytopathogens have the capacity to produce mycotoxins that pose a serious health threat to humans and livestock. To facilitate the transition towards sustainable environmentally friendly agriculture, there is an urgent need to develop innovative methods allowing a reduced use of synthetic fungicides while guaranteeing optimal yields and the safety of the harvests. Several defensins have been reported to display antifungal and even-despite being under-studied-antimycotoxin activities and could be promising natural molecules for the development of control strategies. This review analyses pioneering and recent work addressing the bioactivity of defensins towards fungal phytopathogens; the details of approximately 100 active defensins and defensin-like peptides occurring in plants, mammals, fungi and invertebrates are listed. Moreover, the multi-faceted mechanism of action employed by defensins, the opportunity to optimize large-scale production procedures such as their solubility, stability and toxicity to plants and mammals are discussed. Overall, the knowledge gathered within the present review strongly supports the bright future held by defensin-based plant protection solutions while pointing out the obstacles that still need to be overcome to translate defensin-based in vitro research findings into commercial products.

PaDef (Persea americana var. drymifolia), a Plant Antimicrobial Peptide, Triggers Apoptosis, and Induces Global Epigenetic Modifications on Histone 3 in an Acute Lymphoid Leukemia Cell Line

In recent years, it has been recognized that epigenetic alterations play an important role in the development and maintenance of cancer, including leukemias. Furthermore, it is known that these alterations are involved in the emergence of resistance to conventional chemotherapeutics. Consequently, molecules with an anticancer activity whose activity is ruled by epigenetic modifications are attractive to search for new therapies against cancer. The plant antimicrobial peptides have been widely evaluated as molecules with anticancer activity; however, the analysis of the epigenetic regulation induced by these molecules associated with this activity is scarce and still is an unexplored field. In this work, we show that the PaDef defensin, a plant antimicrobial peptide from Mexican avocado fruit (Persea americana var. drymifolia) is cytotoxic for Jurkat cell line from acute lymphoid leukemia cells, through an apoptotic process. PaDef inhibited cell viability in a concentration-dependent manner, with an IC₅₀ = 47.3 μM. Treatment of Jurkat cells with PaDef (IC₅₀) induced cell death by apoptosis dependent on caspases 8 and 9; besides, it was related to an increase in the production of reactive oxygen species and the loss of mitochondrial membrane potential. Interestingly, the inhibition of caspase activation by inhibitors of caspases 8 and 9 does not revert the reduction in viability, suggesting that other mechanisms, in addition to caspase activity, could be participating in the PaDef cytotoxic effect. Also, the modifications in the histone 3 tails induced by PaDef in Jurkat cells were evaluated, specifically acetylation and methylation. PaDef increased global histone 3 acetylation and lysine 9 specific marks (2-fold and up to 4-fold, respectively). These effects correlated with the reduction of the Histone Deacetylase activity (HDAC, ∼50%). Based on methylation marks, PaDef treatment increased lysine 9 di- and tri-methylation tags (2-fold in both cases). The epigenetic modulation induced by PaDef on Jurkat cells could be related to the chromatin compaction-decompaction promoting gene expression or repression; however, further studies are necessary to correlate these marks with the transcription of specific genes. Therefore, the study of new molecules that may have anticancer activity through epigenetic modulation is interesting.

Molecular targets for antifungals in amino acid and protein biosynthetic pathways

Fungi cause death of over 1.5 million people every year, while cutaneous mycoses are among the most common infections in the world. Mycoses vary greatly in severity, there are long-term skin (ringworm), nail or hair infections (tinea capitis), recurrent like vaginal candidiasis or severe, life-threatening systemic, multiorgan infections. In the last few years, increasing importance is attached to the health and economic problems caused by fungal pathogens. There is a growing need for improvement of the availability of antifungal drugs, decreasing their prices and reducing side effects. Searching for novel approaches in this respect, amino acid and protein biosynthesis pathways appear to be competitive. The route that leads from amino acid biosynthesis to protein folding and its activation is rich in enzymes that are descriptive of fungi. Blocking the action of those enzymes often leads to avirulence or growth inhibition. In this review, we want to trace the principal processes of fungi vitality. We present the data of genes encoding enzymes involved in amino acid and protein biosynthesis, potential molecular targets in antifungal chemotherapy, and describe the impact of inhibitors on fungal organisms.

Antibacterial Activity of Tris NaCl and PBS Buffer Protein Extract of Cassia fistula, Saccharum officinarum, Albizia lebbeck and Cymbopogon citrates Against Bacterial Strains

Medicinal plants are gaining popularity over synthetic medicines because antibiotic resistance demands the alternative source of medication. In the present research, the crude protein extraction of 4 medicinal plants Cassia fistula, Saccharum officinarum, Albizia lebbeck and Cymbopogon citrates was carried out. Crude protein extraction was done by 2 different buffers i.e. Tris NaCl buffer and PBS buffer. Protein confirmation was done by Bradford assay in the spectrophotometer. Antibacterial potential was checked and compared against Escherichia coli, Bacillus subtilis, Neisseria gonorrhoea, Bacillus cereus and Proteus mirabilis. Antibacterial assay was performed by disc diffusion method, agar well method and zones of inhibition were calculated. The study results indicated that Tris NaCl extracts' antimicrobial potential is higher than that of the PBS buffer. On disc diffusion method the Tris NaCl buffer extracts of Cymbopogon citrates showed maximum zone of inhibition 11 mm and 9 mm against Bacillus subtilis and Bacillus cereus respectively and control chloramphenicol showed maximum zone of inhibition 26 mm against Bacillus subtilis. Cassia fistula showed maximum zone of inhibition of 7 mm against Bacillus cereus while Saccharum officinarum and Albizia lebbeck didn't show the any antibacterial activity. On the other hand, Protein extracts from PBS buffer didn't show zone of inhibition against any bacteria. Only Albizia lebbeck showed minute zone of inhibition against Neisseria gonorrhea. On well diffusion method, Cassia fistula Tris NaCl protein extract showed the maximum zone of inhibition 20 mm and 18 mm against Proteus mirabilis and Bacillus subtilis respectively. While Albizia lebbeck PBS protein extract showed the maximum zone of inhibition 19 mm and 17 mm against Bacillus subtilis and Bacillus cereus. The results revealed that the protein extract of Albizia lebbeck, Cymbopogon citrates and Cassia fistula can be used tosynthesize antimicrobial drugs to treat the bacterial infections.

Medicinal Potentialities of Plant Defensins: A Review with Applied Perspectives

Plant-based secondary metabolites with medicinal potentialities such as defensins are small, cysteine-rich peptides that represent an imperative aspect of the inherent defense system. Plant defensins possess broad-spectrum biological activities, e.g., bactericidal and insecticidal actions, as well as antifungal, antiviral, and anticancer activities. The unique structural and functional attributes provide a nonspecific and versatile means of combating a variety of microbial pathogens, i.e., fungi, bacteria, protozoa, and enveloped viruses. Some defensins in plants involved in other functions include the development of metal tolerance and the role in sexual reproduction, while most of the defensins make up the innate immune system of the plants. Defensins are structurally and functionally linked and have been characterized in various eukaryotic microorganisms, mammals, plants, gulls, teleost species of fish, mollusks, insect pests, arachnidan, and crustaceans. This defense mechanism has been improved biotechnologically as it helps to protect plants from fungal attacks in genetically modified organisms (GMO). Herein, we review plant defensins as secondary metabolites with medicinal potentialities. The first half of the review elaborates the origin, structural variations, and mechanism of actions of plant defensins. In the second part, the role of defensins in plant defense, stress response, and reproduction are discussed with suitable examples. Lastly, the biological applications of plant defensins as potential antimicrobial and anticancer agents are also deliberated. In summary, plant defensins may open a new prospect in medicine, human health, and agriculture.

Isolation and Characterization of a Phaseolus vulgaris Trypsin Inhibitor with Antiproliferative Activity on Leukemia and Lymphoma Cells

A 17.5-kDa trypsin inhibitor was purified from Phaseolus vulgaris cv. “gold bean” with an isolation protocol including ion exchange chromatography on DEAE-cellulose (Diethylaminoethyl-cellulose), affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-sepharose (Sulfopropyl-sepharose), and gel filtration by FPLC (Fast protein liquid chromatography) on Superdex 75. It dose-dependently inhibited trypsin with an IC₅₀ value of 0.4 μM, and this activity was reduced in the presence of dithiothreitol in a dose- and time-dependent manner, signifying the importance of the disulfide linkage to the activity. It inhibited [methyl-³H] thymidine incorporation by leukemia L1210 cells and lymphoma MBL2 cells with an IC₅₀ value of 2.3 μM and 2.5 μM, respectively. The inhibitor had no effect on fungal growth and the activities of various viral enzymes when tested up to 100 μM.

Cysteine-stabilized αβ defensins: From a common fold to antibacterial activity

Antimicrobial peptides (AMPs) seem to be promising alternatives to common antibiotics, which are facing increasing bacterial resistance. Among them are the cysteine-stabilized αβ defensins. These peptides are small, with a length ranging from 34 to 54 amino acid residues, cysteine-rich and extremely stable, normally composed of an α-helix and three β-strands stabilized by three or four disulfide bonds and commonly found in several organisms. Moreover, animal and plant CSαβ defensins present different specificities, the first being mainly active against bacteria and the second against fungi. The role of the CSαβ-motif remains unknown, but a common antibacterial mechanism of action, based on the inhibition of the cell-wall formation, has already been observed in some fungal and invertebrate defensins. In this context, the present work aims to group the data about CSαβ defensins, highlighting their evolution, conservation, structural characteristics, antibacterial activity and biotechnological perspectives.

Proteins, peptides, polysaccharides, and nucleotides with inhibitory activity on human immunodeficiency virus and its enzymes

Human immunodeficiency virus (HIV), the causative agent of acquired immune deficiency syndrome, has claimed innumerable lives in the past. Many biomolecules which suppress HIV replication and also other biomolecules that inhibit enzymes essential to HIV replication have been reported. Proteins including a variety of milk proteins, ribosome-inactivating proteins, ribonucleases, antifungal proteins, and trypsin inhibitors; peptides comprising cathelicidins, defensins, synthetic peptides, and others; polysaccharides and polysaccharopeptides; nucleosides, nucleotides, and ribozymes, demonstrated anti-HIV activity. In many cases, the mechanism of anti-HIV action has been elucidated. Strategies have been devised to augment the anti-HIV potency of these compounds.

Plant antifungal proteins and their applications in agriculture

Fungi are far more complex organisms than viruses or bacteria and can develop numerous diseases in plants that cause loss of a substantial portion of the crop every year. Plants have developed various mechanisms to defend themselves against these fungi which include the production of low-molecular-weight secondary metabolites and proteins and peptides with antifungal activity. In this review, families of plant antifungal proteins (AFPs) including defensins, lectins, and several others will be summarized. Moreover, the application of AFPs in agriculture will also be analyzed.

Antibacterial products of marine organisms

Marine organisms comprising microbes, plants, invertebrates, and vertebrates elaborate an impressive array of structurally diverse antimicrobial products ranging from small cyclic compounds to macromolecules such as proteins. Some of these biomolecules originate directly from marine animals while others arise from microbes associated with the animals. It is noteworthy that some of the biomolecules referred to above are structurally unique while others belong to known classes of compounds, peptides, and proteins. Some of the antibacterial agents are more active against Gram-positive bacteria while others have higher effectiveness on Gram-negative bacteria. Some are efficacious against both Gram-positive and Gram-negative bacteria and against drug-resistant strains as well. The mechanism of antibacterial action of a large number of the chemically identified antibacterial agents, possible synergism with currently used antibiotics, and the issue of possible toxicity on mammalian cells and tissues await elucidation. The structural characteristics pivotal to antibacterial activity have been ascertained in only a few studies. Demonstration of efficacy of the antibacterial agents in animal models of bacterial infection is highly desirable. Structural characterization of the active principles present in aqueous and organic extracts of marine organisms with reportedly antibacterial activity would be desirable.

Plant antimicrobial peptides as potential anticancer agents

Antimicrobial peptides (AMPs) are part of the innate immune defense mechanism of many organisms and are promising candidates to treat infections caused by pathogenic bacteria to animals and humans. AMPs also display anticancer activities because of their ability to inactivate a wide range of cancer cells. Cancer remains a cause of high morbidity and mortality worldwide. Therefore, the development of methods for its control is desirable. Attractive alternatives include plant AMP thionins, defensins, and cyclotides, which have anticancer activities. Here, we provide an overview of plant AMPs anticancer activities, with an emphasis on their mode of action, their selectivity, and their efficacy.

Biologically active and antimicrobial peptides from plants

Bioactive peptides are part of an innate response elicited by most living forms. In plants, they are produced ubiquitously in roots, seeds, flowers, stems, and leaves, highlighting their physiological importance. While most of the bioactive peptides produced in plants possess microbicide properties, there is evidence that they are also involved in cellular signaling. Structurally, there is an overall similarity when comparing them with those derived from animal or insect sources. The biological action of bioactive peptides initiates with the binding to the target membrane followed in most cases by membrane permeabilization and rupture. Here we present an overview of what is currently known about bioactive peptides from plants, focusing on their antimicrobial activity and their role in the plant signaling network and offering perspectives on their potential application.

Plant peptides in defense and signaling

This review focuses on plant peptides involved in defense against pathogen infection and those involved in the regulation of growth and development. Defense peptides, defensins, cyclotides and anti-microbial peptides are compared and contrasted. Signaling peptides are classified according to their major sites of activity. Finally, a network approach to creating an interactomic peptide map is described.

Northeast red beans produce a thermostable and pH-stable defensin-like peptide with potent antifungal activity

A 5.4-kDa antifungal peptide was purified from Phaseolus vulgaris L. cv. "northeast red bean" using a protocol that entailed affinity chromatography, ion exchange chromatography, and gel filtration. The molecular mass was determined by matrix-assisted laser desorption ionization time-of-flight. The N-terminal amino acid sequence of the peptide was highly homologous to defensins and defensin-like peptides from several plant species. The peptide impeded the growth of a number of pathogenic fungi, including Mycosphaerella arachidicola Khokhr. (IC50 = 1.7 μM), Setosphaeria turcica Luttr., Fusarium oxysporum Schltdl., and Valsa mali Miyabe & G. Yamada. Antifungal activity of the peptide was fully preserved at temperatures up to 100 °C and pH values from 0 to 12. Congo red deposition at the hyphal tip of M. arachidicola was detected after exposure to the peptide, signifying that the peptide had suppressed hyphal growth. The antifungal peptide did not manifest antiproliferative activity toward human breast cancer MCF7 cells and hepatoma HepG2 cells, in contradiction to the bulk of previously reported plant defensins. The data suggest distinct structural requirements for antifungal and antiproliferative activities.

Synergy of antibacterial and antioxidant activities from crude extracts and peptides of selected plant mixture

BACKGROUND

A plant mixture containing indigenous Australian plants was examined for synergistic antimicrobial activity using selected test microorganisms. This study aims to investigate antibacterial activities, antioxidant potential and the content of phenolic compounds in aqueous, ethanolic and peptide extracts of plant mixture.

METHODS

Well diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays were used to test antibacterial activity against four pathogenic bacteria namely Staphylococcus aureus, Escherichia coli, Bacillus cereus, and Pseudomonas aeruginosa. DPPH (2, 2-diphenyl-1- picrylhydrazyl) and superoxide dismutase (SOD) assays were used to evaluate antioxidant activity. HPLC and gel filtration were used for purification of the peptides. Scanning electron microscope was applied to investigate the mode of attachment of the peptides on target microbial membranes.

RESULTS

Aqueous extraction of the mixture showed no inhibition zones against all the test bacteria. Mean diameter of inhibition zones for ethanol extraction of this mixture attained 8.33 mm, 7.33 mm, and 6.33 mm against S. aureus at corresponding concentrations of 500, 250 and 125 mg/ml while E .coli showed inhibition zones of 9.33 mm, 8.00 mm and 6.66 mm at the same concentrations. B. cereus exhibited inhibition zones of 11.33 mm, 10.33 mm and 10.00 mm at concentrations of 500, 250 and 125 mg/ml respectively. The peptide extract demonstrated antibacterial activity against S. aureus, E. coli and B. cereus. The MIC and MBC values for ethanol extracts were determined at 125 mg/ml concentration against S. aureus and E. coli and B. cereus value was 31.5 mg/ml. MIC and MBC values showed that the peptide extract was significantly effective at low concentration of the Australian plant mixture (APM). Phenolic compounds were detected in hot aqueous and ethanolic extracts of the plant mixture. Hot aqueous, ethanol and peptides extracts also exhibited antioxidant activities.

CONCLUSIONS

It was concluded that APM possessed good antibacterial and antioxidant activities following extraction with different solvents. The results suggest that APM provide a new source with antibacterial agents and antioxidant activity for nutraceutical or medical applications.

A sorghum xylanase inhibitor-like protein with highly potent antifungal, antitumor and HIV-1 reverse transcriptase inhibitory activities

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The antifungal protein purified in this study is a pH stable and thermostable xylanase inhibitor.

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Sorghum antifungal protein is inhibitory toward various fungal species.

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The sorghum antifungal protein exerts suppressive action on the proliferating hepatoma (HepG2) cells and breast cancer (MCF7) cells.

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Sorghum antifungal protein exerts a highly potent inhibitory activity against HIV-1 reverse transcriptase.

A 25-kDa protein, with an N-terminal amino acid sequence homologous to that of xylanase inhibitor and designated as xylanase inbibitor-like protein (XILP) was purified from sorghum seeds. The isolation protocol consisted of affinity chromatography, ion exchange chromatography, and gel filtration. XILP inhibited mycelial growth in various phytopathogenic fungi. The antifungal activity was thermostable and pH-stable. XILP inhibited proliferation of various cancer cell lines but did not do so in human embryonic liver (WRL 68) cells. There was no mitogenic activity toward mouse splenocytes. XILP reduced the activity of HIV-1 reverse transcriptase with an IC₅₀ of 11.1 μM, but lacked inhibitory activity toward HIV-1 integrase and SARS coronavirus proteinase. In conclusion, sorghum XILP is thermostable and pH stable and exhibits potent antifungal, antiproliferative, and HIV-1 reverse transcriptase inhibitory activities.

Biochemical characterization of an anti-Candida factor produced by Enterococcus faecalis

Background

Because Candida albicans is resistant to several antifungal antibiotics, there is a need to identify other less toxic natural products, particularly antimicrobial proteins, peptides or bacteriocin like inhibitory substances. An attempt has been made to purify and characterise an anti-Candida compound produced by Enterococcus faecalis.

Results

An anti-Candida protein (ACP) produced by E. faecalis active against 8 C. albicans strains was characterised and partially purified. The ACP showed a broad-spectrum activity against multidrug resistant C. albicans MTCC 183, MTCC 7315, MTCC 3958, NCIM 3557, NCIM 3471 and DI. It was completely inactivated by treatment with proteinase K and partially by pronase E.

The ACP retained biological stability after heat-treatment at 90°C for 20 min, maintained activity over a pH range 6–10, and remained active after treatment with α-amylase, lipase, organic solvents, and detergents. The antimicrobial activity of the E. faecalis strain was found exclusively in the extracellular filtrate produced in the late logarithmic growth phase. The highest activity (1600 AU mL^-1) against C. albicans MTCC 183 was recorded at 48 h of incubation, and activity decreased thereafter. The peptide showed very low haemagglutination and haemolytic activities against human red blood cells. The antimicrobial substance was purified by salt-fractionation and chromatography.

Partially purified ACP had a molecular weight of approximately 43 KDa in Tricine-PAGE analysis. The 12 amino acid N terminal sequence was obtained by Edman degradation. The peptide was de novo sequenced by ESI-MS, and the deduced combined sequence when compared to other bacteriocins and antimicrobial peptide had no significant sequence similarity.

Conclusions

The inhibitory activity of the test strain is due to the synthesis of an antimicrobial protein. To our knowledge, this is the first report on the isolation of a promising non-haemolytic anti-Candida protein from E. faecalis that might be used to treat candidiasis especially in immunocompromised patients.

A defensin-like peptide from Phaseolus vulgaris cv. 'King Pole Bean'

A 5447 Da antifungal peptide with an N-terminal sequence highly homologous to plant defensins was purified from Phaseolus vulgaris cv. 'King Pole Bean' by anion-exchange chromatography on Q Sepharose and FPLC-gel filtration on Superdex 75. The isolated peptide inhibited growth of a number of fungal species, including Mycosphaerella arachidicola, Saccharomyces cerevisiae and Candida albicans, with IC(50) values of 3.9, 4.0 and 8.4 μM, respectively. Using the membrane non-permeable DNA-binding dye SYTOX green, it was found that the peptide increased the cell membrane permeability of M. arachidicola, S. cerevisiae and C. albicans.

Identification and analysis of common bean (Phaseolus vulgaris L.) transcriptomes by massively parallel pyrosequencing

BACKGROUND

Common bean (Phaseolus vulgaris) is the most important food legume in the world. Although this crop is very important to both the developed and developing world as a means of dietary protein supply, resources available in common bean are limited. Global transcriptome analysis is important to better understand gene expression, genetic variation, and gene structure annotation in addition to other important features. However, the number and description of common bean sequences are very limited, which greatly inhibits genome and transcriptome research. Here we used 454 pyrosequencing to obtain a substantial transcriptome dataset for common bean.

RESULTS

We obtained 1,692,972 reads with an average read length of 207 nucleotides (nt). These reads were assembled into 59,295 unigenes including 39,572 contigs and 19,723 singletons, in addition to 35,328 singletons less than 100 bp. Comparing the unigenes to common bean ESTs deposited in GenBank, we found that 53.40% or 31,664 of these unigenes had no matches to this dataset and can be considered as new common bean transcripts. Functional annotation of the unigenes carried out by Gene Ontology assignments from hits to Arabidopsis and soybean indicated coverage of a broad range of GO categories. The common bean unigenes were also compared to the bean bacterial artificial chromosome (BAC) end sequences, and a total of 21% of the unigenes (12,724) including 9,199 contigs and 3,256 singletons match to the 8,823 BAC-end sequences. In addition, a large number of simple sequence repeats (SSRs) and transcription factors were also identified in this study.

CONCLUSIONS

This work provides the first large scale identification of the common bean transcriptome derived by 454 pyrosequencing. This research has resulted in a 150% increase in the number of Phaseolus vulgaris ESTs. The dataset obtained through this analysis will provide a platform for functional genomics in common bean and related legumes and will aid in the development of molecular markers that can be used for tagging genes of interest. Additionally, these sequences will provide a means for better annotation of the on-going common bean whole genome sequencing.

First report of an anti-tumor, anti-fungal, anti-yeast and anti-bacterial hemolysin from Albizia lebbeck seeds

A monomeric 5.5-kDa protein with hemolytic activity toward rabbit erythrocytes was isolated from seeds of Albizia lebbeck by using a protocol that involved ion-exchange chromatography on Q-Sepharose and SP-Sepharose, hydrophobic interaction chromatography on Phenyl-Sepharose, and gel filtration on Superdex 75. It was unadsorbed on both Q-Sepharose and SP-Sepharose, but adsorbed on Phenyl-Sepharose. Its hemolytic activity was fully preserved in the pH range 0-14 and in the temperature range 0-100 °C, and unaffected in the presence of a variety of metal ions and carbohydrates. The hemolysin reduced viability of murine splenocytes and inhibited proliferation of MCF-7 breast cancer cells and HepG2 hepatoma cells with an IC₅₀ of 0.21, 0.97, and 1.37 μM, respectively. It impeded mycelial growth in the fungi Rhizoctonia solani with an IC₅₀ of 39 μM but there was no effect on a variety of other filamentous fungi, including Fusarium oxysporum, Helminthosporium maydis, Valsa mali and Mycosphaerella arachidicola. Lebbeckalysin inhibited growth of Escherichia coli with an IC₅₀ of 0.52 μM.

Cordymin, an antifungal peptide from the medicinal fungus Cordyceps militaris

Cordymin, an antifungal peptide with a molecular mass of 10,906 Da and an N-terminal amino acid sequence distinct from those of previously reported proteins, was purified from the medicinal mushroom Cordyceps militaris. The isolation protocol comprised ion exchange chromatography of the aqueous extract on SP-Sepharose and Mono S and gel filtration on Superdex 75 by a fast protein liquid chromatography system. Cordymin was adsorbed on both cation exchangers. The peptide inhibited mycelial growth in Bipolaris maydis, Mycosphaerella arachidicola, Rhizoctonia solani and Candida albicans with an IC(50) of 50 μM, 10 μM, 80 μM, and 0.75 mM, respectively. However, there was no effect on Aspergillus fumigatus, Fusarium oxysporum and Valsa mali when tested up to 2 mM. The antifungal activity of the peptide was stable up to 100°C and in the pH range 6-13, and unaffected by 10 mM Zn(2+) and 10 mM Mg(2+). Cordymin inhibited HIV-1 reverse transcriptase with an IC(50) of 55 μM. Cordymin displayed antiproliferative activity toward breast cancer cells (MCF-7) but there was no effect on colon cancer cells (HT-29). There was no mitogenic activity toward mouse spleen cells and no nitric oxide inducing activity toward mouse macrophages when tested up to 1 mM.

Antibacterial peptides from plants: what they are and how they probably work

Plant antibacterial peptides have been isolated from a wide variety of species. They consist of several protein groups with different features, such as the overall charge of the molecule, the content of disulphide bonds, and structural stability under environmental stress. Although the three-dimensional structures of several classes of plant peptides are well determined, the mechanism of action of some of these molecules is still not well defined. However, further studies may provide new evidences for their function on bacterial cell wall. Therefore, this paper focuses on plant peptides that show activity against plant-pathogenic and human-pathogenic bacteria. Furthermore, we describe the folding of several peptides and similarities among their three-dimensional structures. Some hypotheses for their mechanisms of action and attack on the bacterial membrane surface are also proposed.

Purification of a defensin isolated from Vigna unguiculata seeds, its functional expression in Escherichia coli, and assessment of its insect alpha-amylase inhibitory activity

Plant defensins make up a family of cationic antimicrobial peptides with a characteristic three-dimensional folding pattern stabilized by four disulfide bridges. The aim of this work was the purification and functional expression of a defensin from cowpea seeds and the assessment of its alpha-amylase inhibitory activity. The cDNA encoding the cowpea defensin was cloned into the pET-32 EK/LIC vector, and the resulting construct was used to transform Escherichia coli cells. The recombinant peptide was purified via affinity chromatography on a Ni Sepharose column and by reverse-phase chromatography on a C2/C18 column using HPLC. N-terminal amino acid sequencing revealed that the recombinant peptide had a similar sequence to that of the defensin isolated from seeds. The natural and recombinant defensins were submitted to the alpha-amylase inhibition assay. The cowpea seed defensin was found to inhibit alpha-amylases from the weevils Callosobruchus maculatus and Zabrotes subfasciatus. alpha-Amylase inhibition assays also showed that the recombinant defensin inhibited alpha-amylase from the weevil C. maculatus. The cowpea seed defensin and its recombinant form were unable to inhibit mammalian alpha-amylases. The three-dimensional structure of the recombinant defensin was modeled, and the resulting structure was found to be similar to those of other plant defensins.

A peptide with potent antifungal and antiproliferative activities from Nepalese large red beans

An antifungal defensin-like peptide with a molecular mass of 7.1kDa was isolated from dried Nepalese large red beans (Phaseolus angularis). The purification protocol employed included ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-Sepharose, and gel filtration by fast protein liquid chromatography on Superdex 75. The antifungal peptide was unadsorbed on DEAE-cellulose, and adsorbed on Affi-gel blue gel and SP-Sepharose. The antifungal peptide inhibited mycelial growth in Fusarium oxysporum and Mycosphaerella arachidicola with an IC(50) value of 1.4 and 1.8 microM, respectively. It did not inhibit HIV-1 reverse transcriptase when tested up to 200 microM. It exerted an antiproliferative action on L1210 leukemia cells and MBL2 lymphoma cells with an IC(50) of 15 and 60 microM, respectively.

A defensin with highly potent antipathogenic activities from the seeds of purple pole bean

A 5443 Da peptide with sequence homology to defensins was purified from purple pole beans (Phaseolus vulgaris cv. 'Extra-long Purple Pole bean'). This peptide was isolated by adsorption on an affinity chromatographic medium Affi-Gel Blue gel and ion-exchange chromatographic media SP-Sepharose (sulfopropyl-Sepharose) and Mono S and by gel filtration on Superdex peptide. The peptide inhibited mycelial growth in Mycosphaerella arachidicola, Helminthosporium maydis, Fusarium oxysporum, Verticillium dahliae, Rhizoctonia solani, Candida albicans and Setosphaeria turcica with an IC50 of 0.8, 0.9, 2.3, 3.2, 4.3, 4.8 and 9.8 microM respectively. Its antifungal potency was higher than that of the plant defensin coccinin (IC50>50 microM). It induced membrane permeabilization in C. albicans as evidenced by SYTOX Green uptake, but did not affect erythrocyte membrane permeability. It inhibited growth in M. arachidicola by inducing chitin accumulation at hyphal tips as was shown by Congo Red staining. The antifungal activity was pH stable and thermostable. The peptide inhibited the proliferation of hepatoma (HepG2), breast cancer (MCF7), colon cancer (HT29) and cervical cancer (SiHa) cells but not that of human embryonic liver (WRL68) cells. Its anti-HepG2 activity (IC50=4.1+/-0.8 microM, n=3) was higher than that of another plant defensin, gymnin (IC50>50 microM). Its anti-MCF7 activity (IC50=8.3+/-0.3 microM, n=3) was similar to that of other plant defensins. It reduced the activity of HIV-1 reverse transcriptase with an IC50 of 0.5+/-0.1 microM, n=3, much more potently than other plant defensins (IC50>40 microM). There is the possibility of using the purple pole bean defensin for producing antifungal drugs and/or transgenic plants with fungal resistance.

A haemagglutinin from the medicinal fungus Cordyceps militaris

There are only a few reports on agglutinins from ascomycete and medicinal fungi. An HA (haemagglutinin), with an N-terminal amino acid sequence different from those of known lectins, was isolated in the present study from dried fruiting bodies of the medicinal ascomycete fungus Cordyceps militaris. The purification protocol consisted of affinity chromatography, ion-exchange chromatography and gel filtration. The haemagglutinating activity of the HA could not be inhibited by simple sugars or heparin, and was stable over the pH range 2–13 and up to 60°C. Chemical modification of tryptophan and tyrosine residues had no effect. The HA exhibited some antiproliferative activity towards hepatoma (HepG2) cells and inhibited HIV-1 reverse transcriptase (IC50=10 μM). However, it did not exhibit antifungal activity, mitogenic activity towards splenocytes, nitric oxide-inducing activity towards macrophages or RNase activity. The results of the present study add to the meagre information pertaining to agglutinins from ascomycete and medicinal mushrooms. It is revealed in this study that C. militaris HA differs from other ascomycete mushroom HAs in a variety of biochemical characteristics.

Isolation and characterization of juncin, an antifungal protein from seeds of Japanese Takana (Brassica juncea Var. integrifolia)

An 18.9 kDa antifungal protein designated juncin was isolated from seeds of the Japanese takana (Brassica juncea var. integrifolia). The purification protocol employed comprised anion-exchange chromatography on Q-Sepharose, affinity chromatography on Affi-gel blue gel, cation exchange chromatography on SP-Sepharose, and gel filtration on Superdex 75. Juncin was adsorbed on Affi-gel blue gel and SP-Sepharose but unadsorbed on Q-Sepharose. The protein exhibited antifungal activity toward the phytopathogens Fusarium oxysporum, Helminthosporium maydis, and Mycosphaerella arachidicola with IC(50) values of 13.5, 27, and 10 μM, respectively. It was devoid of mitogenic activity toward splenocytes and nitric oxide inducing activity toward macrophages. It inhibited the proliferation of hepatoma (HepG2) and breast cancer (MCF7) cells with IC(50) values of 5.6 and 6.4 μM, respecitvely, and the activity of HIV-1 reverse transcriptase with an IC(50) of 4.5 μM. Its N-terminal sequence differed from those of antifungal proteins that have been reported to date. Compared with Brassica campestris and Brassica alboglabra antifungal peptides, juncin exhibits a different molecular mass and N-terminal amino acid sequence but similar biological activities.

Plant defensins--prospects for the biological functions and biotechnological properties

Plant defensins are a prominent family of cationic peptides in the plant kingdom. They are structurally and functionally related to defensins that have been previously characterized in mammals and insects. They present molecular masses between 5 and 7kDa and possess a pattern of eight conserved Cys residues. The three-dimensional structure of plant defensins is small and globular. It has three anti-parallel beta-sheets and one alpha-helix that is stabilized by a structural motif composed of disulfide bridges. This motif is found in other peptides with biological activity and is called the Cys stabilized alphabeta motif (CSalphabeta). Based on the growing knowledge on defensin structure, gene expression and regulation, and also their in vitro biological activity, it has become clear that plant defensins are complex and sophisticated peptides whose function extends beyond their role in defense of plants against microbial infection. This review discusses recent data and will present comprehensive information regarding the study of defensins.

A thaumatin-like antifungal protein from the emperor banana

A 20-kDa protein with substantial N-terminal sequence homology to thaumatin-like proteins was isolated from ripe fruits of the emperor banana, Musa basjoo cv. 'emperor banana'. The isolation procedure entailed (NH(4))(2)SO(4) precipitation, ion exchange chromatography on DEAE-cellulose, and affinity chromatography on Affi-gel blue gel. The thaumatin-like protein inhibited mycelial growth in Fusarium oxysporum and Mycosphaerella arachidicola. However, it did not affect the mitogenic response of murine splenocytes or [methyl-(3)H] thymidine incorporation by tumor cells. The activity of HIV-1 reverse transcriptase was slightly inhibited.