MucR from Sinorhizobium meliloti: New Insights into Its DNA Targets and Its Ability to Oligomerize.

Proteins of the MucR/Ros family play a crucial role in bacterial infection or symbiosis with eukaryotic hosts. MucR from Sinorhizobium meliloti plays a regulatory role in establishing symbiosis with the host plant, both dependent and independent of Quorum Sensing. Here, we report the first characterization of MucR isolated from Sinorhizobium meliloti by mass spectrometry and demonstrate that this protein forms higher-order oligomers in its native condition of expression by SEC-MALS. We show that MucR purified from Sinorhizobium meliloti can bind DNA and recognize the region upstream of the ndvA gene in EMSA, revealing that this gene is a direct target of MucR. Although MucR DNA binding activity was already described, a detailed characterization of Sinorhizobium meliloti DNA targets has never been reported. We, thus, analyze sequences recognized by MucR in the rem gene promoter, showing that this protein recognizes AT-rich sequences and does not require a consensus sequence to bind DNA. Furthermore, we investigate the dependence of MucR DNA binding on the length of DNA targets. Taken together, our studies establish MucR from Sinorhizobium meliloti as a member of a new family of Histone-like Nucleoid Structuring (H-NS) proteins, thus explaining the multifaceted role of this protein in many species of alpha-proteobacteria.

Deciphering Molecular Determinants Underlying Penicillium digitatum's Response to Biological and Chemical Antifungal Agents by Tandem Mass Tag (TMT)-Based High-Resolution LC-MS/MS.

Penicillium digitatum is a widespread pathogen responsible for the postharvest decay of citrus, one of the most economically important crops worldwide. Currently, chemical fungicides are still the main strategy to control the green mould disease caused by the fungus. However, the increasing selection and proliferation of fungicide-resistant strains require more efforts to explore new alternatives acting via new or unexplored mechanisms for postharvest disease management. To date, several non-chemical compounds have been investigated for the control of fungal pathogens. In this scenario, understanding the molecular determinants underlying P. digitatum's response to biological and chemical antifungals may help in the development of safer and more effective non-chemical control methods. In this work, a proteomic approach based on isobaric labelling and a nanoLC tandem mass spectrometry approach was used to investigate molecular changes associated with P. digitatum's response to treatments with α-sarcin and beetin 27 (BE27), two proteins endowed with antifungal activity. The outcomes of treatments with these biological agents were then compared with those triggered by the commonly used chemical fungicide thiabendazole (TBZ). Our results showed that differentially expressed proteins mainly include cell wall-degrading enzymes, proteins involved in stress response, antioxidant and detoxification mechanisms and metabolic processes such as thiamine biosynthesis. Interestingly, specific modulations in response to protein toxins treatments were observed for a subset of proteins. Deciphering the inhibitory mechanisms of biofungicides and chemical compounds, together with understanding their effects on the fungal physiology, will provide a new direction for improving the efficacy of novel antifungal formulations and developing new control strategies.

Molecular Fingerprint of Human Pathological Synoviocytes in Response to Extractive Sulfated and Biofermentative Unsulfated Chondroitins.

Pharma-grade extractive chondroitin sulfate (CS) is widely used for osteoarthritis (OA) treatment. Recently, unsulfated biofermentative chondroitin (BC) proved positive effects in OA in vitro model. This study, based on primary pathological human synoviocytes, aimed to analyze, by a multiplex assay, a panel of OA-related biomarkers in response to short-term treatments with bovine (CSb), pig (CSp) and fish (CSf) chondroitins, in comparison to BC. As expected, all samples had anti-inflammatory properties, however CSb, CSf and especially BC affected more cytokines and chemokines. Based on these results and molecular weight similarity, CSf and BC were selected to further explore the synoviocytes' response. In fact, Western blot analyses showed CSf and BC were comparable, downregulating OA-related biomarkers such as the proteins mTOR, NF-kB, PTX-3 and COMP-2. Proteomic analyses, performed by applying a nano-LC-MS/MS TMT isobaric labelling-based approach, displayed the modulation of both common and distinct molecules to chondroitin treatments. Thus, CSf and BC modulated the biological mediators involved in the inflammation cascade, matrix degradation/remodeling, glycosaminoglycans' synthesis and cellular homeostasis. This study helps in shedding light on different molecular mechanisms related to OA disease that may be potentially affected not only by animal-source chondroitin sulfate but also by unsulfated biofermentative chondroitin.

The Structural Characterization and Antipathogenic Activities of Quinoin, a Type 1 Ribosome-Inactivating Protein from Quinoa Seeds.

Quinoin is a type 1 ribosome-inactivating protein (RIP) we previously isolated from the seeds of pseudocereal quinoa (Chenopodium quinoa) and is known as a functional food for its beneficial effects on human health. As the presence of RIPs in edible plants could be potentially risky, here we further characterised biochemically the protein (complete amino acid sequence, homologies/differences with other RIPs and three-dimensional homology modeling) and explored its possible defensive role against pathogens. Quinoin consists of 254 amino acid residues, without cysteinyl residues. As demonstrated by similarities and homology modeling, quinoin preserves the amino acid residues of the active site (Tyr75, Tyr122, Glu177, Arg180, Phe181 and Trp206; quinoin numbering) and the RIP-fold characteristic of RIPs. The polypeptide chain of quinoin contains two N-glycosylation sites at Asn115 and Asp231, the second of which appears to be linked to sugars. Moreover, by comparative MALDI-TOF tryptic peptide mapping, two differently glycosylated forms of quinoin, named pre-quinoin-1 and pre-quinoin-2 (~0.11 mg/100 g and ~0.85 mg/100 g of seeds, respectively) were characterised. Finally, quinoin possesses: (i) strong antiviral activity, both in vitro and in vivo towards Tobacco Necrosis Virus (TNV); (ii) a growth inhibition effect on the bacterial pathogens of plants; and (iii) a slight antifungal effect against two Cryphonectria parasitica strains.

Development of a New Highly Selective Monoclonal Antibody against Preferentially Expressed Antigen in Melanoma (PRAME) and Identification of the Target Epitope by Bio-Layer Interferometry.

BACKGROUND: Monoclonal antibodies (mAbs) against cancer biomarkers are key reagents in diagnosis and therapy. One such relevant biomarker is a preferentially expressed antigen in melanoma (PRAME) that is selectively expressed in many tumors. Knowing mAb's epitope is of utmost importance for understanding the potential activity and therapeutic prospective of the reagents. METHODS: We generated a mAb against PRAME immunizing mice with PRAME fragment 161-415; the affinity of the antibody for the protein was evaluated by ELISA and SPR, and its ability to detect the protein in cells was probed by cytofluorimetry and Western blotting experiments. The antibody epitope was identified immobilizing the mAb on bio-layer interferometry (BLI) sensor chip, capturing protein fragments obtained following trypsin digestion and performing mass spectrometry analyses. RESULTS: A mAb against PRAME with an affinity of 35 pM was obtained and characterized. Its epitope on PRAME was localized on residues 202-212, taking advantage of the low volumes and lack of fluidics underlying the BLI settings. CONCLUSIONS: The new anti-PRAME mAb recognizes the folded protein on the surface of cell membranes suggesting that the antibody's epitope is well exposed. BLI sensor chips can be used to identify antibody epitopes.

Interactome mapping defines BRG1, a component of the SWI/SNF chromatin remodeling complex, as a new partner of the transcriptional regulator CTCF.

The highly conserved zinc finger CCCTC-binding factor (CTCF) regulates genomic imprinting and gene expression by acting as a transcriptional activator or repressor of promoters and insulator of enhancers. The multiple functions of CTCF are accomplished by co-association with other protein partners and are dependent on genomic context and tissue specificity. Despite the critical role of CTCF in the organization of genome structure, to date, only a subset of CTCF interaction partners have been identified. Here we present a large-scale identification of CTCF-binding partners using affinity purification and high-resolution LC-MS/MS analysis. In addition to functional enrichment of specific protein families such as the ribosomal proteins and the DEAD box helicases, we identified novel high-confidence CTCF interactors that provide a still unexplored biochemical context for CTCF's multiple functions. One of the newly validated CTCF interactors is BRG1, the major ATPase subunit of the chromatin remodeling complex SWI/SNF, establishing a relationship between two master regulators of genome organization. This work significantly expands the current knowledge of the human CTCF interactome and represents an important resource to direct future studies aimed at uncovering molecular mechanisms modulating CTCF pleiotropic functions throughout the genome.

Differential Secretome Profiling of Human Osteoarthritic Synoviocytes Treated with Biotechnological Unsulfated and Marine Sulfated Chondroitins.

Symptomatic slow-acting drugs (SYSADOA) are increasingly used as effective therapies for osteoarthritis, representing an attractive alternative to analgesics or non-steroidal anti-inflammatory drugs to relieve disease symptoms. Pharmaceutical preparations of chondroitin sulfate, derived from animal sources, alone or in combination with glucosamine sulfate, are widely recognized for their beneficial effect on osteoarthritis treatment. A growing interest has also been devoted to understanding the molecular mechanisms modulated by SYSADOA using -omic strategies, most of which rely on chondrocytes as a model system. In this work, by using an integrated strategy based on unbiased proteomics and targeted cytokine profiling by a multiplexed protein array, we identified differences in the secretomes of human osteoarthritic synoviocytes in response to biotechnological unsulfated, and marine sulfated chondroitins treatments. The combined strategy allowed the identification of candidate proteins showing both common and distinct regulation responses to the two treatments of chondroitins. These molecules, mainly belonging to ECM proteins, enzymes, enzymatic inhibitors and cytokines, are potentially correlated to treatment outcomes. Overall, the present results provide an integrated overview of protein changes in human osteoarthritic synoviocytes secretome associated to different chondroitin treatments, thus improving current knowledge of the biochemical effects driven by these drugs potentially involved in pathways associated to osteoarthritis pathogenesis.

Exploring the Interaction between the SWI/SNF Chromatin Remodeling Complex and the Zinc Finger Factor CTCF.

The transcription factor CCCTC-binding factor (CTCF) modulates pleiotropic functions mostly related to gene expression regulation. The role of CTCF in large scale genome organization is also well established. A unifying model to explain relationships among many CTCF-mediated activities involves direct or indirect interactions with numerous protein cofactors recruited to specific binding sites. The co-association of CTCF with other architectural proteins such as cohesin, chromodomain helicases, and BRG1, further supports the interplay between master regulators of mammalian genome folding. Here, we report a comprehensive LC-MS/MS mapping of the components of the switch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex co-associated with CTCF including subunits belonging to the core, signature, and ATPase modules. We further show that the localization patterns of representative SWI/SNF members significantly overlap with CTCF sites on transcriptionally active chromatin regions. Moreover, we provide evidence of a direct binding of the BRK-BRG1 domain to the zinc finger motifs 4-8 of CTCF, thus, suggesting that these domains mediate the interaction of CTCF with the SWI/SNF complex. These findings provide an updated view of the cooperative nature between CTCF and the SWI/SNF ATP-dependent chromatin remodeling complexes, an important step for understanding how these architectural proteins collaborate to shape the genome.

Muskox myoglobin: purification, characterization and kinetics studies compared with cattle and water buffalo myoglobins.

BACKGROUND: The Arctic muskox has economic potential as an alternative meat species and is becoming increasingly popular. The present study aimed to determine the primary structure and pseudoperoxidase activity of muskox myoglobin (Mb) compared to cattle and water buffalo myoglobins. RESULTS: The primary structure of muskox Mb was determined via a matrix-assisted laser desorption ionization-time of flight mass spectrometry-based mapping approach using the sheep Mb as a reference sequence. The muskox Mb consists of 153 amino acid residues and shows 100% identity with sheep Mb, whereas 98.69% and 97.38% identity is found with cattle and water buffalo Mbs, respectively. Muskox Mb has an autoxidation rate (MetMb formation) higher than both cattle and water buffalo Mbs at pH 7.2 (37 °C). Moreover, its pseudoperoxidase activity is higher than both cattle and water buffalo Mbs at pH 7.4 (physiological pH), whereas it is slightly lower than cattle Mb and higher than water buffalo at a lower pH (5.8), corresponding to the conditions in meat. CONCLUSION: For the first time, the present study reports the purification of myoglobin from muskoxen and, furthermore, a comparative study is conducted on autoxidation and pseudoperoxidase activity with respect to cattle and water buffalo Mbs at both physiological and acid pH. Overall, the results of the current research provide novel information for future studies useful to the meat industry when considering the importance of myoglobin as a principal pigment in meat colour stability. © 2019 Society of Chemical Industry.

A robust nanoLC high-resolution mass spectrometry methodology for the comprehensive profiling of lactic acid bacteria in milk kefir.

Consumer attention to functional foods containing probiotics is growing because of their positive effects on human health. Kefir is a fermented milk beverage produced by bacteria and yeasts. Given the emerging kefir market, there is an increasing demand for new methodologies to certify product claims such as colony-forming units/g and bacterial taxa. MALDI-TOF MS proved to be useful for the detection/identification of bacteria in clinical diagnostics and agri-food applications. Recently, LC-MS/MS approaches have also been applied to the identification of proteins and proteotypic peptides of lactic acid bacteria in fermented food matrices. Here, we developed an innovative nanoLC-ESI-MS/MS-based methodology for profiling lactic acid bacteria in commercial and artisanal milk kefir products as well as in kefir grains at the genus, species and subspecies level. The proposed workflow enables the authentication of kefir label claims declaring the presence of probiotic starters. An overview of the composition of lactic acid bacteria was also obtained for unlabelled kefir highlighting, for the first time, the great potential of LC-MS/MS as a sensitive tool to assess the authenticity of fermented foods.

Nusinersen mitigates neuroinflammation in severe spinal muscular atrophy patients.

BACKGROUND: Neuroinflammation contributes to the onset and progression of neurodegenerative diseases, but has not been specifically investigated in patients affected by severe and milder forms of spinal muscular atrophy (SMA). METHODS: In this two-center retrospective study, we investigated signatures of neuroinflammation in forty-eight pediatric male and female SMA1 (n = 18), male and female SMA2 (n = 19), and female SMA3 (n = 11) patients, as well as in a limited number of male and female non-neurological control subjects (n = 4). We employed a Bio-Plex multiplex system based on xMAP technology and performed targeted quantitative analysis of a wide range of pro- and anti-inflammatory cytokines (chemokines, interferons, interleukins, lymphokines and tumor necrosis factors) and neurotrophic factors in the cerebrospinal fluid (CSF) of the study cohort before and after Nusinersen treatment at loading and maintenance stages. RESULTS: We find a significant increase in the levels of several pro-inflammatory cytokines (IL-6, IFN-γ, TNF-α, IL-2, IL-8, IL-12, IL-17, MIP-1α, MCP-1, and Eotaxin) and neurotrophic factors (PDGF-BB and VEGF) in the CSF of SMA1 patients relative to SMA2 and SMA3 individuals, who display levels in the range of controls. We also find that treatment with Nusinersen significantly reduces the CSF levels of some but not all of these neuroinflammatory molecules in SMA1 patients. Conversely, Nusinersen increases the CSF levels of proinflammatory G-CSF, IL-8, MCP-1, MIP-1α, and MIP-1ß in SMA2 patients and decreases those of anti-inflammatory IL-1ra in SMA3 patients. CONCLUSIONS: These findings highlight signatures of neuroinflammation that are specifically associated with severe SMA and the neuro-immunomodulatory effects of Nusinersen therapy.

Spinal muscular atrophy (SMA) is an inherited disorder which leads to muscle weakening. Three therapies have recently been developed, including Nusinersen. However, the effect of SMA on the immune system and how this could be affected by Nusinersen is unknown. The immune system protects the body from infection and, in some disorders, misfunctions and damages the body in the absence of infection. Here, we analyze components of the immune system in body fluids from SMA patients before and after treatment with Nusinersen. The immune system was found to be more active in patients with more severe disease. Treatment with Nusinersen reduced the levels of some, but not all of these, components of the immune system. Thus, treatments that impact the immune system might improve symptoms in patients with SMA.

The PTX3/TLR4 autocrine loop as a novel therapeutic target in triple negative breast cancer.

BACKGROUND: The pattern recognition receptor long pentraxin-3 (PTX3) plays conflicting roles in cancer by acting as an oncosuppressor or as a pro-tumor mediator depending on tumor context. Triple negative breast cancer (TNBC) represents the most aggressive histotype of breast cancer, characterized by the lack of efficacious therapeutic targets/approaches and poor prognosis. Thus, the characterization of new molecular pathways and/or alternative druggable targets is of great interest in TNBC. METHODS: The expression of PTX3 in BC tumor samples and in BC cell lines has been analyzed using the Gene Expression-Based Outcome for Breast Cancer Online (GOBO), qPCR, Western blot and ELISA assay. The contribution of tumor and stromal cells to PTX3 production in TNBC was assessed by analyzing single cell RNA sequencing data and RNAscope performed on TNBC tumor samples. In order to investigate the effects of PTX3 in TNBC, different cell lines were engineered to knock-down (MDA-MB-231 and BT549 cells) or overexpress (MDA-MB-468 and E0771 cells) PTX3. Finally, using these engineered cells, in vitro (including gene expression profiling and gene set enrichment analyses) and in vivo (orthotopic tumor models in immune-compromised and immune competent mice) analyses were performed to assess the role and the molecular mechanism(s) exerted by PTX3 in TNBC. RESULTS: In silico and experimental data indicate that PTX3 is mainly produced by tumor cells in TNBC and that its expression levels correlate with tumor stage. Accordingly, gene expression and in vitro results demonstrate that PTX3 overexpression confers a high aggressive/proliferative phenotype and fosters stem-like features in TNBC cells. Also, PTX3 expression induces a more tumorigenic potential when TNBC cells are grafted orthotopically in vivo. Conversely, PTX3 downregulation results in a less aggressive behavior of TNBC cells. Mechanistically, our data reveal that PTX3 drives the activation of the pro-tumorigenic Toll-like receptor 4 (TLR4) signaling pathway in TNBC, demonstrating for the first time that the PTX3/TLR4 autocrine stimulation loop contributes to TNBC aggressiveness and that TLR4 inhibition significantly impacts the growth of PTX3-producing TNBC cells. CONCLUSION: Altogether, these data shed light on the role of tumor-produced PTX3 in TNBC and uncover the importance of the PTX3/TLR4 axis for therapeutic and prognostic exploitation in TNBC.

Structure and Biological Properties of Ribosome-Inactivating Proteins and Lectins from Elder (Sambucus nigra L.) Leaves.

Ribosome-inactivating proteins (RIPs) are a group of proteins with rRNA N-glycosylase activity that catalyze the removal of a specific adenine located in the sarcin-ricin loop of the large ribosomal RNA, which leads to the irreversible inhibition of protein synthesis and, consequently, cell death. The case of elderberry (Sambucus nigra L.) is unique, since more than 20 RIPs and related lectins have been isolated and characterized from the flowers, seeds, fruits, and bark of this plant. However, these kinds of proteins have never been isolated from elderberry leaves. In this work, we have purified RIPs and lectins from the leaves of this shrub, studying their main physicochemical characteristics, sequences, and biological properties. In elderberry leaves, we found one type 2 RIP and two related lectins that are specific for galactose, four type 2 RIPs that fail to agglutinate erythrocytes, and one type 1 RIP. Several of these proteins are homologous to others found elsewhere in the plant. The diversity of RIPs and lectins in the different elderberry tissues, and the different biological activities of these proteins, which have a high degree of homology with each other, constitute an excellent source of proteins that are of great interest in diagnostics, experimental therapy, and agriculture.

The mismatch-repair proteins MSH2 and MSH6 interact with the imprinting control regions through the ZFP57-KAP1 complex.

BACKGROUND: Imprinting Control Regions (ICRs) are CpG-rich sequences acquiring differential methylation in the female and male germline and maintaining it in a parental origin-specific manner in somatic cells. Despite their expected high mutation rate due to spontaneous deamination of methylated cytosines, ICRs show conservation of CpG-richness and CpG-containing transcription factor binding sites in mammalian species. However, little is known about the mechanisms contributing to the maintenance of a high density of methyl CpGs at these loci. RESULTS: To gain functional insights into the mechanisms for maintaining CpG methylation, we sought to identify the proteins binding the methylated allele of the ICRs by determining the interactors of ZFP57 that recognizes a methylated hexanucleotide motif of these DNA regions in mouse ESCs. By using a tagged approach coupled to LC-MS/MS analysis, we identified several proteins, including factors involved in mRNA processing/splicing, chromosome organization, transcription and DNA repair processes. The presence of the post-replicative mismatch-repair (MMR) complex components MSH2 and MSH6 among the identified ZFP57 interactors prompted us to investigate their DNA binding profile by chromatin immunoprecipitation and sequencing. We demonstrated that MSH2 was enriched at gene promoters overlapping unmethylated CpG islands and at repeats. We also found that both MSH2 and MSH6 interacted with the methylated allele of the ICRs, where their binding to DNA was mediated by the ZFP57/KAP1 complex. CONCLUSIONS: Our findings show that the MMR complex is concentrated on gene promoters and repeats in mouse ESCs, suggesting that maintaining the integrity of these regions is a primary function of highly proliferating cells. Furthermore, the demonstration that MSH2/MSH6 are recruited to the methylated allele of the ICRs through interaction with ZFP57/KAP1 suggests a role of the MMR complex in the maintenance of the integrity of these regulatory regions and evolution of genomic imprinting in mammalian species.

Myoglobin from Atlantic and Tinker mackerels: Purification, characterization and its possible use as a molecular marker.

Here, we report the characterization (purification, autoxidation rate, pseudoperoxidase activity) and amino acid sequence determination of S. scombrus (Atlantic mackerel) and S. colias (Tinker mackerel) mioglobins (Mbs), considering the increasing consumption of fresh and canned mackerel meat and Mb implication in meat storage (e.g.: browning and lipid oxidation). We found that Atlantic mackerel Mb has major autoxidation rate (0.204 ± 0.013 h-1) compared to Tinker mackerel Mb (0.140 ± 0.009 h-1), while the pseudoperoxidase activity is major for Tinker mackerel (Km: 87.71 ± 7.19 µM; kcat: 0.32 s-1) Mb with respect to Atlantic mackerel (Km: 96.08 ± 6.91 µM; kcat: 0.50 s-1). These functional differences are confirmed by primary structure determination, in which six amino acid substitutions are found, with the first N-terminal amino acid residue acetylated. Furthermore, we predicted by AphaFold 3D model both fish Mbs and used them to investigate the possible structural differences. In addition, phylogenetic analysis using Mb sequences from Scombridae family confirms that Atlantic and Tinker mackerels are two distinct species. Finally, an analytic qualitative RP-HPLC method to distinguish S. scombrus and S. colias specimens was developed considering the different retention times of the two mackerel apoMbs.

Ca2+ as activator of pseudoperoxidase activity of pigeon, Eurasian woodcock and chicken myoglobins: New features for meat preservation studies.

Myoglobin (Mb), hemeprotein that binds dioxygen in muscle, affects meat colour. Moreover, in presence of peroxides, metMb is a potent oxidant involved in oxidative rancidity in meat. Here, following pigeon Mb purification and primary structure mass spectroscopy characterization, we determined its autoxidation rate and pseudoperoxidase activity with respect to chicken and E. woodcock Mbs. The three Mbs exhibit different autoxidation rates (0.153-h-1 pigeon, 0.194-h-1 chicken and 0.220-h-1 E. woodcock Mbs) and similar specificity constant (9.86x103 M-1s-1 pigeon, 8.81x103 M-1s-1 chicken and 9.90x103 M-1s-1 E. woodcock Mbs), considering their pseudoperoxidase activity. Moreover, for the first time, we detected an increase in pseudoperoxidase activity in presence of Ca2+, particularly at pH 5.8. NMR and CD data indicate that the nonspecific Ca2+ binding induces small local structural rearrangements that in turn slightly reduce pigeon Mb thermal stability. However, considering Ca2+ concentration variations before and post-mortem, this finding must be considered for meat preservation.

Mass spectrometry-based protein and peptide profiling for food frauds, traceability and authenticity assessment.

The ever-growing use of mass spectrometry (MS) methodologies in food authentication and traceability originates from their unrivalled specificity, accuracy and sensitivity. Such features are crucial for setting up analytical strategies for detecting food frauds and adulterations by monitoring selected components within food matrices. Among MS approaches, protein and peptide profiling has become increasingly consolidated. This review explores the current knowledge on recent MS techniques using protein and peptide biomarkers for assessing food traceability and authenticity, with a specific focus on their use for unmasking potential frauds and adulterations. We provide a survey of the current state-of-the-art instrumentation including the most reliable and sensitive acquisition modes highlighting advantages and limitations. Finally, we summarize the recent applications of MS to protein/peptide analyses in food matrices and examine their potential in ensuring the quality of agro-food products.

Ageritin from Pioppino Mushroom: The Prototype of Ribotoxin-Like Proteins, a Novel Family of Specific Ribonucleases in Edible Mushrooms.

Ageritin is a specific ribonuclease, extracted from the edible mushroom Cyclocybe aegerita (synonym Agrocybe aegerita), which cleaves a single phosphodiester bond located within the universally conserved alpha-sarcin loop (SRL) of 23-28S rRNAs. This cleavage leads to the inhibition of protein biosynthesis, followed by cellular death through apoptosis. The structural and enzymatic properties show that Ageritin is the prototype of a novel specific ribonucleases family named 'ribotoxin-like proteins', recently found in fruiting bodies of other edible basidiomycetes mushrooms (e.g., Ostreatin from Pleurotus ostreatus, Edulitins from Boletus edulis, and Gambositin from Calocybe gambosa). Although the putative role of this toxin, present in high amount in fruiting body (>2.5 mg per 100 g) of C. aegerita, is unknown, its antifungal and insecticidal actions strongly support a role in defense mechanisms. Thus, in this review, we focus on structural, biological, antipathogenic, and enzymatic characteristics of this ribotoxin-like protein. We also highlight its biological relevance and potential biotechnological applications in agriculture as a bio-pesticide and in biomedicine as a therapeutic and diagnostic agent.

Ribotoxin-like proteins from Boletus edulis: structural properties, cytotoxicity and in vitro digestibility.

Porcini are edible mushrooms widely used in cooking due to their extraordinary taste. Despite this, cases of food poisoning have been reported in the recent literature also for ingestion of porcini. Here, we report the isolation from Boletus edulis fruiting bodies of two novel ribotoxin-like proteins (RL-Ps), enzymes already studied in other organisms for their toxicity. These RL-Ps, named Edulitin 1 (16-kDa) and Edulitin 2 (14-kDa), show peculiar structural and enzymatic differences, which probably reflect their different bio-activities and a dose/time dependent toxicity (Edulitin 2) on normal and tumoral human cells. Particularly interesting is the resistance to proteolysis of Edulitin 2, for which it was observed that its toxicity was abolished only after heat treatment (90 °C) followed by proteolysis. As mushroom poisoning is a serious food safety issue, data here presented confirm the existence of toxins also in porcini and the importance of a proper cooking before their consumption.

Correlation of structure, function and protein dynamics in myoglobins from Eurasian woodcock, chicken and ostrich.

Myoglobin (Mb), oxygen-binding heme-protein retrieved primarily in muscles, is a local oxygen reservoir providing to oxygen when oxygen delivery is insufficient during catabolism. Furthermore, Mb structure is studied as example of molecular evolution for its ability to respond to environmental pressures and adapt to it through few amino acid substitutions. Here, in order to explore the structure-function-dynamics relationships of Eurasian woodcock chicken and ostrich Mbs we have applied an integrated approach in which spectroscopic and biochemical data have been coupled to computational techniques as structural modelling and molecular dynamics simulations. The primary structure of E. woodcock Mb, reveals the presence of 3 (i.e. Q34H, E44D and V66A) and 10 (i.e. A19T, E27A, V28I, K50T, D53E, G57A, D60E, N81K, S84A and A120S) amino acid substitutions respect to chicken and ostrich Mbs, respectively. Although the high amino acid sequence identity, E. woodcock Mb displays a higher autoxidation rate than chicken and ostrich Mb, despite of a similar melting temperature (T m ∼ 358 K). Yet, the 3D structural models validated by using experimental data indicate that the three Mbs adopt an almost identical three-dimensional structure conserving the typical secondary and tertiary structural organization. Interestingly, dynamics data reveal that the E. woodcock Mb exhibits greater internal motions than either chicken or ostrich Mbs. Overall, our study demonstrates that in Mbs the functional properties are significantly driven by the protein dynamic peculiarities, which in turn depend on the amino acid composition of the region located in proximity of the pathways for the gas ligands. [Formula: see text] Communicated by Ramaswamy H. Sarma.