Purification and Characterization of a Nonspecific Lipid Transfer Protein 1 (nsLTP1) from Ajwain (Trachyspermum ammi) Seeds

Proteomic characterization and cytotoxic potential of proteins from Cuscuta (Cuscuta epithymum (L.) crude herbal product against MCF-7 human breast cancer cell line

BACKGROUND

The burden of breast cancer, the second leading cause of death worldwide, is increasing at an alarming rate. Cuscuta, used in traditional medicine for different ailments, including cancer, is known for containing phytochemicals that exhibit anticancer activity; however, the bioactivities of proteins from this plant remain unexplored. This study aimed to screen the cytotoxic potential of proteins from the crude herbal product of Cuscuta epithymum(L.) (CE) harvested from the host plants Alhagi maurorum and Medicago sativa.

METHODS

The proteins from CE were extracted using a salting-out method, followed by fractionation with a gel filtration chromatography column. Gel-free shotgun proteomics was subsequently performed for protein characterization. The viability assay using MTT was applied to deduce the cytotoxic potential of proteins against MCF-7 breast cancer cells, with further exploration of the effect of treatment on the expression of the apoptotic mediator BCL2-associated X protein (BAX) and B-cell lymphoma protein 2 (BCL-2) proteins, using western blotting to strengthen the findings from the in vitro viability assay.

RESULTS

The crude proteins (CP) of CE were separated into four protein peaks (P1, P2, P3, and P4) by gel filtration chromatography. The evaluation of potency showed a dose-dependent decline in the MCF-7 cell line after CP, P1, P2, and P3 treatment with the respective IC50 values of 33.8, 43.1, 34.5, and 28.6 µg/ml. The percent viability of the cells decreased significantly upon treatment with 50 µg/ml CP, P1, P2, and P3 (P < 0.001). Western-blot analysis revealed upregulation of proapoptotic protein BAX in the cells treated with CP, P3 (P < 0.01), and P2 (P < 0.05); however, the antiapoptotic protein, BCL-2 was downregulated in the cells treated with CP and P3 (P < 0.01), but no significant change was detected in P2 treated cells. The observed cytotoxic effects of proteins in the CP, P1, P2, and P3 from the in vitro viability assay and western blot depicted the bioactivity potential of CE proteins. The database search revealed the identities of functionally important proteins, including nonspecific lipid transfer protein, superoxide dismutase, carboxypeptidase, RNase H domain containing protein, and polyribonucleotide nucleotidyltransferase, which have been previously reported from other plants to exhibit anticancer activity.

CONCLUSION

This study indicated the cytotoxic activity of Cuscuta proteins against breast cancer MCF-7 cells and will be utilized for future investigations on the mechanistic effect of active proteins. The survey of CE proteins provided substantial data to encourage further exploration of biological activities exhibited by proteins in Cuscuta.

Production of Plant Proteins and Peptides with Pharmacological Potential

The use of plant proteins or peptides in biotechnology is based on their identification as possessing bioactive potential in plants. This is usually the case for antimicrobial, fungicidal, or insecticidal components of the plant's defense system. They function in addition to a large number of specialized metabolites. Such proteins can be classified according to their sequence, length, and structure, and this has been tried to describe for a few examples here. Even though such proteins or peptides can be induced during plant-pathogen interaction, they are still present in rather small amounts that make the system not suitable for the production in large-scale systems. Therefore, a suitable type of host needs to be identified, such as cell cultures or adult plants. Bioinformatic predictions can also be used to add to the number of bioactive sequences. Some problems that can occur in production by the plant system itself will be discussed, such as choice of promoter for gene expression, posttranslational protein modifications, protein stability, secretion of proteins, or induction by elicitors. Finally, the plant needs to be set up by biotechnological or molecular methods for production, and the product needs to be enriched or purified. In some cases of small peptides, a direct chemical synthesis might be feasible. Altogether, the process needs to be considered marketable.

Expeditious profiling of polycyclic aromatic hydrocarbons transport and obstruction mechanisms in crop xylem sap proteins via proteomics and molecular docking

Polycyclic aromatic hydrocarbons (PAHs) pose significant environmental risks due to their toxicity and carcinogenic properties. This research seeks to pinpoint protein targets in crop xylem sap related to PAH contamination and delve into their protein-ligand interactions using computational tools. Proteomic assessment revealed differentially expressed proteins (DEPs), which were subjected to virtual high-throughput screening. Notably, the phenanthrene's influence on xylem sap proteins in maize and wheat was more pronounced than in soybean, with DEPs expression peak at 24 h post-treatment. Maize DEPs were predominantly associated with lipid biosynthesis. Phenanthrene impacted cell membrane hydrophobicity, limiting PAH adsorption and decreasing its concentration in maize xylem sap. Wheat DEPs exhibited an increase in ABC transporters after 24 h of phenanthrene exposure. ABC transporters interacted with stress-responsive proteins like C6TIY1-Co-chaperone p23 and others that either facilitate or inhibit PAH transport, including Indeno[1,2,3-cd]Pyrene and C6TIY1-Co-chaperone protein p23. Both maize and wheat created high-affinity complexes between specific proteins and PAHs, influencing their transport. This study provides insights into the mechanisms of PAH regulation and movement within plant xylem.

Molecular allergology and its application in prevention, diagnosis and therapy

Allergic diseases represent a relevant global health problem, affecting adults and children and posing a significant burden for health care systems. In addition, the disease is still under-recognized and harmonized diagnostic tools and management plans for patients are still lacking. In this review the most important aspects of the diagnosis of allergic diseases are summarized and the contribution of Molecular allergology to this area is highlighted.

Purification and thermodynamic characterization of acid protease with novel properties from Melilotus indicus leaves

A thermostable acid protease from M. indicus leaves was purified 10-fold using a 4-step protocol. We were able to isolate a purified protease fraction with a molecular weight of 50 kDa and exhibited maximal protease activity at pH 4.0 and 40 °C. Structural analysis revealed that the protease is monomeric and non-glycosylated. The addition of epoxy monocarboxylic acid, iodoacetic acid, and dimethyl sulfoxide significantly reduced protease activity while dramatically increasing the inhibition of Mn²⁺, Fe²⁺, and Cu²⁺. The activation energy of the hydrolysis reaction (33.33 kJ mol^-1) and activation energy (E_d = 105 kJ mol^-1), the standard enthalpy variation of reversible protease unfolding (2.58 kJ/mol) were calculated after activity measurements at various temperatures. Thermal inactivation of the pure enzyme followed first-order kinetics. The half-life (t_1/2) of the pure enzyme at 50 °C, 60 °C, and 70 °C was 385, 231, and 154 min, respectively. Thermodynamic parameters (entropy and enthalpy) suggested that the protease was highly thermostable. This is the first report on the thermodynamic parameters of proteases produced by M. indicus. The novel protease appears to be particularly thermostable and may be important for industrial applications based on these thermodynamic properties.

Features and Possible Applications of Plant Lipid-Binding and Transfer Proteins

In plants, lipid trafficking within and inside the cell is carried out by lipid-binding and transfer proteins. Ligands for these proteins are building and signaling lipid molecules, secondary metabolites with different biological activities due to which they perform diverse functions in plants. Many different classes of such lipid-binding and transfer proteins have been found, but the most common and represented in plants are lipid transfer proteins (LTPs), pathogenesis-related class 10 (PR-10) proteins, acyl-CoA-binding proteins (ACBPs), and puroindolines (PINs). A low degree of amino acid sequence homology but similar spatial structures containing an internal hydrophobic cavity are common features of these classes of proteins. In this review, we summarize the latest known data on the features of these protein classes with particular focus on their ability to bind and transfer lipid ligands. We analyzed the structural features of these proteins, the diversity of their possible ligands, the key amino acids participating in ligand binding, the currently known mechanisms of ligand binding and transferring, as well as prospects for possible application.

Lipid transfer proteins involved in plant-pathogen interactions and their molecular mechanisms

Nonspecific lipid transfer proteins (LTPs) are small, cysteine-rich proteins that play numerous functional roles in plant growth and development, including cutin wax formation, pollen tube adhesion, cell expansion, seed development, germination, and adaptation to changing environmental conditions. LTPs contain eight conserved cysteine residues and a hydrophobic cavity that provides a wide variety of lipid-binding specificities. As members of the pathogenesis-related protein 14 family (PR14), many LTPs inhibit fungal or bacterial growth, and act as positive regulators in plant disease resistance. Over the past decade, these essential immunity-related roles of LTPs in plant immune processes have been documented in a growing body of literature. In this review, we summarize the roles of LTPs in plant-pathogen interactions, emphasizing the underlying molecular mechanisms in plant immune responses and specific LTP functions.

Mechanistic insights into phenanthrene acropetal translocation via wheat xylem: Separation and identification of transfer proteins

Polycyclic aromatic hydrocarbons (PAHs) have the potential to cause cancer, teratogenicity, and mutagenesis in humans. Long-term plant safe production relies on how PAHs are transported and coordinated across organs. However, the acropetal transfer mechanism of PAHs in staple crop stems, particularly in xylem, a critical path, is unknown. Herein, we first confirmed the presence of specific interaction between the proteins and phenanthrene by employing the magnetic phenanthrene-bound bead immunoassay and label free liquid chromatograph mass spectrometer (LC-MS/MS), suggesting that peroxidase (uniprot accession: A0A3B5XXD0) and unidentified proteins (uniprot accession: A0A3B6LUC6) may function as the carriers to load and acropetally translocate phenanthrene (a model PAH) in wheat xylem. This specified binding of protein-phenanthrene may form through hydrophobic interactions in the conservative binding region, as revealed by protein structural investigations and molecular docking. To further investigate the role of these proteins in phenanthrene solubilization, phenanthrene exposure was conducted: a substantial quantity of peroxidase was produced; an unusually high expression of uncharacterized proteins was observed, indicating their positive effects in the acropetal transfer of phenanthrene in wheat xylem. These data confirmed that the two proteins are crucial in the solubilization of phenanthrene in wheat xylem sap. Our findings provide fresh light on the molecular mechanism of PAH loading in plant xylem and techniques for ensuring the security of staple crops and improving the efficacy of phytoremediation in a PAH-contaminated environment.

Plant-Derived Antimicrobial Peptides: Novel Preservatives for the Food Industry

Food spoilage is a widespread issue brought on by the undesired growth of microbes in food products. Thousands of tons of usable food or food products are wasted every day due to rotting in different parts of the world. Several food preservation techniques are employed to prevent food from rotting, including the use of natural or manufactured chemicals or substances; however, the issue persists. One strategy for halting food deterioration is the use of plant-derived antimicrobial peptides (AMPs), which have been investigated for possible bioactivities against a range of human, plant, and food pathogens. The food industry may be able to benefit from the development of synthetic AMPs, produced from plants that have higher bioactivity, better stability, and decreased cytotoxicity as a means of food preservation. In order to exploit plant-derived AMPs in various food preservation techniques, in this review, we also outline the difficulties in developing AMPs for use as commercial food preservatives. Nevertheless, as technology advances, it will soon be possible to fully explore the promise of plant-derived AMPs as food preservatives.

Cytotoxic activity of non-specific lipid transfer protein (nsLTP1) from Ajwain (Trachyspermum ammi) seeds

Background

Trachyspermum ammi, commonly known as Ajwain, is a member of the Apiaceae family. It is a therapeutic herbal spice with diverse pharmacological properties, used in traditional medicine for various ailments. However, all previous studies were conducted using small molecule extracts, leaving the protein’s bioactivity undiscovered.

Aim

The current study aimed to demonstrate the cytotoxic activity of Ajwain non-specific lipid transfer protein (nsLTP1) in normal breast (MCF10A), breast cancer (MCF-7), and pancreatic cancer (AsPC-1) cell lines. Also, to evaluate its structural stability in human serum as well as at high temperature conditions.

Methods

The cytotoxic activity of Ajwain nsLTP1 was evaluated in MCF-7 and AsPC-1 cell lines using MTT assay. Annexin V-FITC and PI staining were used to detect the early apoptotic and late apoptotic cells. The role of nsLTP1 in inducing apoptosis was further studied by quantifying Bcl-2, Bax, Caspase-3, Survivin, EGFR, and VEGF genes expression using RT-PCR. CD spectroscopy analyzed the nsLTP1 conformational changes after thermal treatment for structure stability determination. The RP-HPLC was used to analyze the nsLTP1 degradation rate in human serum at different time intervals incubated at 37 °C.

Results

Ajwain nsLTP1 showed a potent cytotoxic effect in MCF-7 and AsPC-1. The IC₅₀ value obtained in MCF-7 was 8.21 μM, while for AsPC-1 4.17 μM. The effect of nsLTP1 on stimulating apoptosis revealed that the proportions of apoptotic cells in both cell lines were relatively increased depending on the concentration. The apoptotic cells percentage at 20 μM was in MCF-7 71% (***P < 0.001) and AsPC-1 88% (***P < 0.001). These results indicate that nsLTP1 might efficaciously induce apoptosis in multiple types of cancerous cells. Genes expression in MCF-7 and AsPC-1 showed significant upregulation in Bax and Caspase-3 and downregulation in Bcl-2, Survivin, EGFR, and VEGF protein. The CD analysis of nsLTP1 showed a significant thermostable property. In serum, nsLTP1 showed a slow degradation rate, indicating high stability with a half-life of ~ 8.4 h.

Conclusion

Our results revealed the potential anticancer activity of Ajwain nsLTP1 and its mechanism in inducing apoptosis. It further exhibited thermostable properties at high temperatures and in human serum, which suggested this protein as a promising anticancer agent.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03616-y.

Plant non-specific lipid transfer proteins: An overview

Plant non-specific lipid transfer proteins (nsLTPs) are usually defined as small, basic proteins, with a wide distribution in all orders of higher plants. Structurally, nsLTPs contain a conserved motif of eight cysteines, linked by four disulphide bonds, and a hydrophobic cavity in which the ligand is housed. This structure confers stability and enhances the ability to bind and transport a variety of hydrophobic molecules. Their highly conserved structural resemblance but low sequence identity reflects the wide variety of ligands they can carry, as well as the broad biological functions to which they are linked to, such as membrane stabilization, cell wall organization and signal transduction. In addition, they have also been described as essential in resistance to biotic and abiotic stresses, plant growth and development, seed development, and germination. Hence, there is growing interest in this family of proteins for their critical roles in plant development and for the many unresolved questions that need to be clarified, regarding their subcellular localization, transfer capacity, expression profile, biological function, and evolution.

Ceramide-1-phosphate transfer protein promotes sphingolipid reorientation needed for binding during membrane interaction

Lipid transfer proteins acquire and release their lipid cargoes by interacting transiently with source and destination biomembranes. In the GlycoLipid Transfer Protein (GLTP) superfamily, the two-layer all-α-helical GLTP-fold defines proteins that specifically target sphingolipids (SLs) containing either sugar or phosphate headgroups via their conserved but evolutionarily-modified SL recognitions centers. Despite comprehensive structural insights provided by X-ray crystallography, the conformational dynamics associated with membrane interaction and SL uptake/release by GLTP superfamily members have remained unknown. Herein, we report insights gained from molecular dynamics (MD) simulations into the conformational dynamics that enable ceramide-1-phosphate transfer proteins (CPTPs) to acquire and deliver ceramide-1-phosphate (C1P) during interaction with 1-palmitoyl-2-oleoyl phosphatidylcholine bilayers. The focus on CPTP reflects this protein's involvement in regulating pro-inflammatory eicosanoid production and autophagy-dependent inflammasome assembly that drives interleukin (IL-1β and IL-18) production and release by surveillance cells. We found that membrane penetration by CPTP involved α-6 helix and the α-2 helix N-terminal region, was confined to one bilayer leaflet, and was relatively shallow. Large-scale dynamic conformational changes were minimal for CPTP during membrane interaction or C1P uptake except for the α-3/α-4 helices connecting loop, which is located near the membrane interface and interacts with certain phosphoinositide headgroups. Apart from functioning as a shallow membrane-docking element, α-6 helix was found to adeptly reorient membrane lipids to help guide C1P hydrocarbon chain insertion into the interior hydrophobic pocket of the SL binding site.These findings support a proposed 'hydrocarbon chain-first' mechanism for C1P uptake, in contrast to the 'lipid polar headgroup-first' uptake used by most lipid-transfer proteins.

Lipid Transfer Proteins (LTPs)-Structure, Diversity and Roles beyond Antimicrobial Activity

Lipid transfer proteins (LTPs) are among the most promising plant-exclusive antimicrobial peptides (AMPs). They figure among the most challenging AMPs from the point of view of their structural diversity, functions and biotechnological applications. This review presents a current picture of the LTP research, addressing not only their structural, evolutionary and further predicted functional aspects. Traditionally, LTPs have been identified by their direct isolation by biochemical techniques, whereas omics data and bioinformatics deserve special attention for their potential to bring new insights. In this context, new possible functions have been identified revealing that LTPs are actually multipurpose, with many additional predicted roles. Despite some challenges due to the toxicity and allergenicity of LTPs, a systematic review and search in patent databases, indicate promising perspectives for the biotechnological use of LTPs in human health and also plant defense.

Biotechnological applications of versatile plant lipid transfer proteins (LTPs)

Plant AMPs are usually cysteine-rich, and can be classified in several classes, including lipid transfer proteins (LTPs). LTPs are small plant cationic peptides, and can be classified in two subclasses, LTP₁ (9-10 kDa) and LTP₂ (7 kDa). They have been identified and isolated from various plant species and can be involved in a number of processes, including responses against several phytopathogens. LTP₁ presents 4 parallel α- helices and a 3₁₀-helix fragment. These structures form a tunnel with large and small entrances. LTP₂ presents 3 parallel α- helices, which form a cavity with triangular structure. Both LTP subclasses present a hydrophobic cavity, which makes interaction with different lipids and general hydrophobic molecules possible. Several studies report a broad spectrum of activity of plant LTPs, including antibacterial, antifungal, antiviral, antitumoral, and insecticidal activity. Thus, these molecules can be employed in human and animal health as an alternative to the conventional treatment of disease, well as providing the source of novel drugs. However, employing peptides in human health can present challenges, such as the toxicity of peptides, the difference between the results found in in vitro assays and in pre-clinical or clinical tests and their low efficiency against Gram-negative bacteria. In this context, plant LTPs can be an interesting alternative means by which to bypass such challenges. This review addresses the versatility of plant LTPs, their broad spectrum of activities and their potential applications in human and animal health and in agricultural production, and examines challenges in their biotechnological application.

Structural characterization and in vitro lipid binding studies of non-specific lipid transfer protein 1 (nsLTP1) from fennel (Foeniculum vulgare) seeds

Non-specific lipid transfer proteins (nsLTPs) are cationic proteins involved in intracellular lipid shuttling in growth and reproduction, as well as in defense against pathogenic microbes. Even though the primary and spatial structures of some nsLTPs from different plants indicate their similar features, they exhibit distinct lipid-binding specificities signifying their various biological roles that dictate further structural study. The present study determined the complete amino acid sequence, in silico 3D structure modeling, and the antiproliferative activity of nsLTP1 from fennel (Foeniculum vulgare) seeds. Fennel is a member of the family Umbelliferae (Apiaceae) native to southern Europe and the Mediterranean region. It is used as a spice medicine and fresh vegetable. Fennel nsLTP1 was purified using the combination of gel filtration and reverse-phase high-performance liquid chromatography (RP-HPLC). Its homogeneity was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry. The purified nsLTP1 was treated with 4-vinyl pyridine, and the modified protein was then digested with trypsin. The complete amino acid sequence of nsLTP1 established by intact protein sequence up to 28 residues, overlapping tryptic peptides, and cyanogen bromide (CNBr) peptides. Hence, it is confirmed that fennel nsLTP1 is a 9433 Da single polypeptide chain consisting of 91 amino acids with eight conserved cysteines. Moreover, the 3D structure is predicted to have four α-helices interlinked by three loops and a long C-terminal tail. The lipid-binding property of fennel nsLTP1 is examined in vitro using fluorescent 2-p-toluidinonaphthalene-6-sulfonate (TNS) and validated using a molecular docking study with AutoDock Vina. Both of the binding studies confirmed the order of binding efficiency among the four studied fatty acids linoleic acid > linolenic acid > Stearic acid > Palmitic acid. A preliminary screening of fennel nsLTP1 suppressed the growth of MCF-7 human breast cancer cells in a dose-dependent manner with an IC50 value of 6.98 µM after 48 h treatment.

Antiproliferative and apoptotic effects of proteins from black seeds (Nigella sativa) on human breast MCF-7 cancer cell line

Background

Nigella sativa (NS), a member of family Ranunculaceae is commonly known as black seed or kalonji. It has been well studied for its therapeutic role in various diseases, particularly cancer. Literature is full of bioactive compounds from NS seed. However, fewer studies have been reported on the pharmacological activity of proteins. The current study was designed to evaluate the anticancer property of NS seed proteins on the MCF-7 cell line.

Methods

NS seed extract was prepared in phosphate-buffered saline (PBS), and proteins were precipitated using 80% ammonium sulfate. The crude seed proteins were partially purified using gel filtration chromatography, and peaks were resolved by SDS-PAGE. MTT assay was used to screen the crude proteins and peaks for their cytotoxic effects on MCF-7 cell line. Active Peaks (P1 and P4) were further studied for their role in modulating the expression of genes associated with apoptosis by real-time reverse transcription PCR. For protein identification, proteins were digested, separated, and analyzed with LC-MS/MS. Data analysis was performed using online Mascot, ExPASy ProtParam, and UniProt Knowledgebase (UniProtKB) gene ontology (GO) bioinformatics tools.

Results

Gel filtration chromatography separated seed proteins into seven peaks, and SDS-PAGE profile revealed the presence of multiple protein bands. Among all test samples, P1 and P4 depicted potent dose-dependent inhibitory effect on MCF-7 cells exhibiting IC₅₀ values of 14.25 ± 0.84 and 8.05 ± 0.22 μg/ml, respectively. Gene expression analysis demonstrated apoptosis as a possible cell killing mechanism. A total of 11 and 24 proteins were identified in P1 and P4, respectively. The majority of the proteins identified are located in the cytosol, associate with biological metabolic processes, and their molecular functions are binding and catalysis. Hydropathicity values were mostly in the hydrophilic range.

Conclusion

Our findings suggest NS seed proteins as a potential therapeutic agent for cancer. To our knowledge, it is the first study to report the anticancer property of NS seed proteins.