Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the separation of proteins in the range from 1 to 100 kDa

Chemosensory protein 16 has an immune function and participates in host-pathogen interaction in Galleria mellonella infected with Pseudomonas entomophila

Chemosensory protein 16 was identified in the hemolymph of Galleria mellonella as a protein with an amount increasing after oral infection with 10^3 CFU of Pseudomonas entomophila, and decreasing after infection with a higher dose (10^5 CFU) of bacteria. The expression of the CSP16 gene occurred in the fat body and in the gut and correlated with changes in the protein level in the hemolymph. The CSP16 protein inhibited P. entomophila growth in the concentration range from 0.15 to 6 nM. Additionally, the CSP16 protein showed bactericidal activity against P. entomophila, Bacillus thuringiensis, and Escherichia coli in the range of 2-18 μM, but only in the presence of protease inhibitors, otherwise it was degraded by extracellular proteases secreted by P. entomophila. We demonstrated that the bactericidal activity of CSP16 was related to its ability to perforate bacterial cellular membranes in a dose-dependent manner. The antimicrobial properties of this protein were also confirmed with the use of Atomic Force Microscopy, which showed significant changes in the topology of different bacterial cell surfaces. Finally, when CSP16 was injected in vivo into G. mellonella larvae one hour after infection with P. entomophila, more survivors were observed at particular time-points. Taking into account its immune properties and putative ability to bind bacteria-derived compounds, the possible function of CSP16 in the host-pathogen interaction is discussed.

An alternative mechanism by which If1 prevents ATP hydrolysis by the ATP synthase subcomplex in S. cerevisiae

The mitochondrial F1F0-ATP synthase is crucial for maintaining the ATP/ADP balance which is critical for cell metabolism, ion homeostasis and cell proliferation. This enzyme, conserved across evolution, is found in the mitochondria or chloroplasts of eukaryotic cells and the plasma membrane of bacteria. In vitro studies have shown that the mitochondrial F1F0-ATP synthase is reversible, capable of hydrolyzing instead of synthesizing ATP. In vivo, its reversibility is inhibited by the endogenous peptide If1 (Inhibitory Factor 1), which specifically prevents ATP hydrolysis in a pH-dependent manner. Despite its presumed importance, the loss of If1 in various model organisms does not cause severe phenotypes, suggesting its role may be confined to specific stress or metabolic conditions yet to be discovered. Our analyses indicate that inhibitory peptides are crucial in mitigating mitochondrial depolarizing stress under glyco-oxidative metabolic conditions. Additionally, we found that the absence of If1 destabilizes the nuclear-encoded free F1 subcomplex. This mechanism highlights the role of If1 in preventing harmful ATP wastage, offering new insights into its function under physiological and pathological conditions.

Antifungal, Antimycobacterial, Protease and α‒Amylase Inhibitory Activities of a Novel Serine Bifunctional Protease Inhibitor from Adenanthera pavonina L. Seeds

Antifungal resistance poses a significant challenge to disease management, necessitating the development of novel drugs. Antimicrobial peptides offer potential solutions. This study focused on extraction and characterization of peptides from Adenanthera pavonina seeds with activity against Candida species, Mycobacterium tuberculosis, proteases, and α-amylases. Peptides were extracted in phosphate buffer and heated at 90°C for 10 min to create a peptide rich heated fraction (PRHF). After confirming antimicrobial activity and the presence of peptides, the PRHF underwent ion exchange chromatography, yielding retained and non-retained fractions. These fractions were evaluated for antimicrobial activity and cytotoxicity against murine macrophages. The least toxic and most active fraction underwent reversed-phase chromatography, resulting in ten fractions. These fractions were tested for peptides and antimicrobial activity. The most active fraction was rechromatographed on a reversed-phase column, resulting in two fractions that were assessed for antimicrobial activity. The most active fraction revealed a single band of approximately 6 kDa and was tested for inhibitory effects on proteases and α-amylases. Thermal stability experiments were conducted on the 6 kDa peptide at different temperatures followed by reassessment of antifungal activity and circular dichroism. The 6 kDa peptide inhibited yeasts, M. tuberculosis, human salivary and Tenebrio molitor larvae intestine α-amylases, and proteolytic activity from fungal extracts, and thus named ApPI. Remarkably, ApPI retained antifungal activity and conformation after heating and is primarily composed of α-helices. ApPI is a thermally stable serine protease/α-amylase inhibitor from A. pavonina seeds, offering promise as a foundational molecule for innovative therapeutic agents against fungal infections and tuberculosis.

Antimicrobial Peptides (Bacteriocins) Produced by Lactococcus lactis and Pediococcus pentosaceus Strains with Activity Against Clinical and Food-Borne Pathogens

Bacteriocins are ribosomal-synthesized peptides with antimicrobial activity, produced by different groups of bacteria, including lactic acid bacteria (LAB). Most of the produced by LAB bacteriocins can be described with rather broad spectra of inhibition and they offer suggested applications in food preservation and pharmaceutical sector. Different LAB were isolated from fermented food products and fruits, obtained from the region of Pohang, Korea, and identified based on physiological, biochemical, and molecular methods. The promising isolates, Pediococcus pentosaceus 732, Lactococcus lactis 808, and Lactococcus lactis subsp. lactis 431, were identified based on biochemical, physiological, and biomolecular approaches, including 16S rRNA partial sequencing, and were evaluated for production of bacteriocin, including stability in presence of enzymes, chemicals, pH, and temperatures. Adherence properties for the expressed bacteriocins by P. pentosaceus 732, Lc. lactis 808, and Lc. lactis subsp. lactis 431 were evaluated at presence of selected chemicals, pH, and temperatures. The presence of bacteriocin genes in the strains was investigated and analyzed. The bacterial effect of bacteriocin produced by studied strains on Listeria spp. and Staphylococcus spp. has been shown for actively growing and stationary cells. Similar growth and bacteriocin production were observed when studied strains were cultured in MRS at 30 °C or 37 °C. The presence of nisin operon with some point mutations on the genomic DNA was recorded based on the performed PCR reactions targeting different genes associated with nisin expression for both lactococcal strains. Pediocin PA-1 operon was evaluated in a similar manner for P. pentosaceus 732.

Acute targeting of N-terminal tau protein has long-lasting beneficial effects in Tg2576 APP/Aβ mouse model by reducing cognitive impairment, cerebral Aβ-amyloidosis, synaptic remodeling and microgliosis later in life

Even though the number of patients suffering from Alzheimer's Disease (AD) is rapidly growing worldwide, only a few symptomatic treatments have been approved for clinical use, pointing out the urgent need for more effective disease-modifying therapies that actually alter the progression of this neurodegenerative disorder which is characterized by co-occurence of both Amyloid beta (Aβ) and tau neuropathologies. Preclinical and clinical evidence suggests that a link between Aβ and tau drives the entire continuum of AD pathobiology. 12A12 is a monoclonal antibody (mAb) which offers neuroprotection into two transgenic lines of AD, including Tg2576 that overexpresses Swedish mutation (KM670/671NL) of Amyloid Precursor Protein (APP, isoform 695) and 3xTg (APP Swedish, MAPT P301L, and PSEN1 M146V), by targeting the 20-22kDa N-terminal tau fragments (NH2htau). In particular, acute (over 14 days with 4 doses), intravenous injection of 12A12mAb leads to significant improvement of cognitive, biochemical and histopathological AD signs in symptomatic 6-month-old Tg2576, a well-established transgenic mouse model that mimics the human amyloidosis with an age-dependent Aβ accumulation/aggregation and plaque deposition. Here, we report that Tg2576 mice, immunized with 12A12mAb at 6 months of age and returned to their home cage for additional 3 months, exhibit preserved spatial memory despite the anticipated interruption of antibody administration (discontinuous treatment). This enduring beneficial effect on memory deficit (up to 90 days after the last injection) is accompanied by normalization in the synaptic imbalance and microgliosis along with decrease of the most toxic A11-positive prefibrillar oligomers and inverse increase in 4kDa monomeric form(s) of Aβ 1-42. These findings reveal that: (i) soluble, pathogenetic tau specie(s) located at the N-terminal domain of protein early synergizes with Aβ in driving the progression of AD neuropathology; (ii) transient immunoneutralization of the NH2htau following short-term treatment with 12A12mAb exerts preventive, long-lasting neuroprotective effects, at least in part by interfering at "pre-plaque" stage with the progressive deposition of insoluble, fibrillar Aβ via a shift of its aggregation pathway into its less harmful, unaggregated monomeric forms. Taken together, these findings represent a strong rationale for the advancement of 12A12mAb to clinical stage aiming at preventing the Aβ-dependent neurodegeneration by lowering the cerebral levels of NH2htau in humans suffering from chronic, slow-progressing AD.

Bio-induced overproduction of heterocycloanthracin-like bacteriocin in Lysinibacillus macroides by Aspergillus austroafricanus: optimization of medium conditions and evaluation of potential applications

BACKGROUND

Plants and microorganisms are at the forefront of natural exploitable bioresources for the discovery of novel bioactive compounds (BACs) to provide solutions to food and agricultural challenges. The present study aimed to produce a novel biotechnologically-relevant BAC from a mangrove sediment bacterium under optimized bioprocess medium conditions. The BAC-producing bacteria were isolated via the crowded plate technique, and medium optimization was performed via sequential statistics of response surface methodology (RSM). The RSM model predictions were optimized, validated, and scaled up in a 5-L bioreactor via submerged batch fermentation. The BAC was extracted with ethyl acetate, purified via silica gel column chromatography, and identified via semipreparative high-performance liquid chromatography using bioactive standards with known retention times. The biocontrol, antioxidant and biopreservation potential of the BAC were evaluated via standard methods.

RESULTS

The results revealed that strain GKRMS-A9 produced the largest inhibition zone diameter (ZND) of 17 mm against the susceptible mould. The bacterium and its susceptible mould were identified as Lysinibacillus macroides and Aspergillus austroafricanus strains, respectively. Bioprocess medium optimization produced 9.6 g L- 1 of the BAC with a ZND of 47.1 mm using 44.84% [v v- 1] rice processing effluent, 8.58 gL- 1 casamino acid, 1.39 g L- 1 MgSO4.7H2O, 2.78 g L- 1 CaCl2.2H2O, 16.94% [v v- 1] inoculum volume, and 10.45 g L- 1 Na2HPO4/NaH2PO4. The BAC concentration increased 48.7-fold in response to biological induction with susceptible mould. Silica gel chromatography revealed 9 bioactive fractions in the ethyl acetate extract, with fraction C (retention time of 9.02 min) eliciting the largest mean ZND of 38.1 ± 1.7 mm against Aspergillus austroafricanus. Fraction C was identified as a heterocycloanthracin-like class II bacteriocin with a molecular weight of 10.5 kDa.

CONCLUSION

The bacteriocin 'macroidin' is stable over a wide range of pH values and temperatures and has significant antimicrobial activity against Gram-positive food-borne and phytopathogenic strains of bacteria and moulds. Its antioxidant activities against DPPH and ABTS*+ radicals are comparable to those of ascorbic acid, making this biomolecule a promising agent for biopreservation and phytopathogen control applications in the food and agricultural sectors.

A Holistic Investigation of Arabidopsis Proteomes Altered in Chloroplast Biogenesis and Retrograde Signalling Identifies PsbO as a Key Regulator of Chloroplast Quality Control

Communication between the diverse compartments of plant cells relies on an intricate network of molecular interactions that orchestrate organellar development and adaptation to environmental conditions. Plastid-to-nucleus signalling pathways play a key role in relaying information from developing, mature, and damaged or disintegrating chloroplasts to the nucleus, which serves to coordinate gene expression between the two genomes. To shed light on these mechanisms, we performed a comprehensive analysis of the response of the Arabidopsis thaliana proteomes to perturbation of chloroplast biogenesis by the antibiotic lincomycin (Lin) in the absence of GENOMES UNCOUPLED 1 (GUN1), a key player in plastid-to-nucleus signalling. The topological analysis of protein-protein interactions (PPIs) and co-expression networks enabled the identification of protein hubs in each genotype and condition tested, and highlighted whole-cell adaptive responses to the disruption of chloroplast biogenesis. Our findings reveal a novel role for PsbO, a subunit of the oxygen-evolving complex (OEC), which behaves as an atypical photosynthetic protein upon inhibition of plastid protein synthesis. Notably, and unlike all other subunits of the thylakoid electron transport chain, PsbO accumulates in non-photosynthetic plastids, and is crucial for the breakdown of damaged chloroplasts.

Proteome-wide determinants of co-translational chaperone binding in bacteria

Chaperones are essential to the co-translational folding of most proteins. However, the principles of co-translational chaperone interaction throughout the proteome are poorly understood, as current methods are restricted to few substrates and cannot capture nascent protein folding or chaperone binding sites, precluding a comprehensive understanding of productive and erroneous protein biosynthesis. Here, by integrating genome-wide selective ribosome profiling, single-molecule tools, and computational predictions using AlphaFold we show that the binding of the main E. coli chaperones involved in co-translational folding, Trigger Factor (TF) and DnaK correlates with "unsatisfied residues" exposed on nascent partial folds - residues that have begun to form tertiary structure but cannot yet form all native contacts due to ongoing translation. This general principle allows us to predict their co-translational binding across the proteome based on sequence only, which we verify experimentally. The results show that TF and DnaK stably bind partially folded rather than unfolded conformers. They also indicate a synergistic action of TF guiding intra-domain folding and DnaK preventing premature inter-domain contacts, and reveal robustness in the larger chaperone network (TF, DnaK, GroEL). Given the complexity of translation, folding, and chaperone functions, our predictions based on general chaperone binding rules indicate an unexpected underlying simplicity.

Coordinated Transcriptional Increases in Cell Wall Synthesis Genes in Neisseria gonorrhoeae Lacking the Lytic Transglycosylase, ltgA

Lytic transglycosylase A in Neisseria gonorrhoeae cleaves the β-1,4-glycosidic bond between peptidoglycan (PG) monomers to liberate 1,6-anhydro-PG fragments that are either recycled or released as cytotoxic fragments. To gain further insight into the effect of LtgA on cellular processes in Neisseria gonorrhoeae, we performed a proteomic analysis comparing wild-type and an isogenic ltgA null mutant strain. Proteins were separated by two-dimensional gel electrophoresis and identified by MALDI-TOF mass spectrometry, which revealed several proteins that were increased in their level of expression upon loss of LtgA. The most notable changes corresponded to enzymes related to aminosugar and pyrimidine metabolism. Quantitative real-time RT-PCR of mRNA from a ltgA null strain confirmed increased transcription of genes encoding enzymes involved in UDP-N-acetylglucosamine (UDP-GlcNAc) synthesis, a major precursor in PG and lipooligosaccharide (LOS) synthesis, during normal growth conditions and following exposure to penicillin. We also found that the ltgA mutant strains were more susceptible to β-lactam antibiotics, vancomycin, and the human-cathelicidin antibacterial peptide, LL-37, than their corresponding wild-type parental strains. Our results suggest that increased expression of enzymes responsible for production UDP-GlcNAc is an adaptive response due to inactivation of ltgA and/or exposure to penicillin.

Purification and characterization of a bacteriocin produced by the probiotic Lactiplantibacillus plantarum subsp. argentoratensis strain I1B

This study is aimed to characterize a broad-spectrum bacteriocin produced by Lactiplantibacillus plantarum subsp. argentoratensis strain I1B of fermented food origin and also to evaluate the in vitro probiotic properties of this strain. Cell supernatant of this strain showed broad-spectrum antibacterial activity against five prominent foodborne pathogens viz. Salmonella typhi 950, Escherichia coli 728, Yersinia enterocolitica 861, Listeria monocytogenes 657, and Klebsiella pneumoniae 618 with the strongest activity against the S. typhi 950. Cell supernatant also exhibited stability to proteolytic enzyme treatment, pH, and temperature. Optimum bacteriocin production was at 20-24 h of incubation in MRS broth at 37 °C with pH 6.0. The bacteriocin activity was retained in the 70% ammonium sulfate precipitate fraction, which was further purified using gel filtration chromatography (Sephadex G25 column) to the level of a single band on the SDS-PAGE and the activity was confirmed by zymogram. The molecular mass of the bacteriocin was found to be 22,199 Daltons. The pure molecule was identified using LC-MS/MS and was found to be an Adherence Protein with a sequence of chitin-binding domain consisting of 201 amino acid residues. The isolated strain exhibited potential probiotic activity within the established regulations and did not raise any possible safety concerns. This work reports a potent bacteriocin produced by a listed probiotic organism with latent postbiotic activity which could be used as a potential biopreservatives.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-025-04279-5.

Dispensability of a positively charged residue at Lys11 in staphylokinase for plasminogen activation

The exposure of a positively charged residue, lysine11 (Lys11), at the N-terminus following proteolytic cleavage of the Lys10-Lys11 peptide bond, is necessary for the plasminogen activation by staphylokinase (SAK) from Staphylococcus aureus. However, in many natural variants of SAK, Lys11 is substituted by isoleucine (Ile) or valine (Val). The role of these N-terminal amino acid substitutions in modulating the plasminogen activation ability of SAK remains unknown. To investigate the molecular mechanism by which Lys11 and its substitutions at the N-terminus of SAK modulate its plasminogen activation potentiality, we performed substitution and deletion mutagenesis of Lys11, combined with structural modelling of bimolecular complexes of these mutants with micro-plasmin. SAK mutants carrying substitutions of Lys11 with Ile or Val exhibited N-terminal processing and catalytic efficiency for plasminogen activation comparable to wild-type SAK. In contrast, the substitution of Lys11 with alanine (Ala) drastically reduced its plasminogen activation ability, despite maintaining N-terminal processing similar to wild-type SAK. These findings suggest that Lys11 at the N-terminus of SAK can be functionally replaced with Ile or Val. However, unlike streptokinase, the presence of Ile at the N-terminus of SAK does not enable non-proteolytic activation of plasminogen. Structural models of SAK and its mutants in complex with micro-plasmin revealed that the flexible N-terminus extends towards the active site at the interphase of Asp646 within a distance of 4 Å, favouring direct interactions between the exposed Lys, Ile, or Val residues similar to other serine proteases, thereby altering substrate specificity of plasmin towards plasminogen activation.

A role in intracellular K+ in protecting pathogenic dimorphic fungi against induced cell death by bioinspired antimicrobial peptides

Antimicrobial peptides (AMPs) are promising drugs, though their fungal combat mechanisms remain partly unclear. We designed three AMPs (dAMPs) based on the γ-core of the Vu-Def1 seed defensin from Vigna unguiculata L. Walp. named RR, D-RR, and WR, and assessed their actions on Candida tropicalis and Candida albicans. Amidst their actions are cell shrinkage caused by K+ efflux from fungal cells. K+ involvement in fungal death by these peptides was explored. We assessed cell shrinkage, oxidative stress, mitochondria hyperpolarization, membrane permeabilization, medium acidification, antimicrobial activity under hypoosmotic conditions, and cellular degradation. Viability assays were performed with channel blockers and K+ addition at various times. The interactions of dAMPs with salts and fungal cells were analyzed using circular dichroism and microscopy. K+ and Cl- channels were not directly involved in dAMPs-induced death. Supplementation with K+ protected fungal cells from death. In tests, cations often deactivated them through charge neutralization. Peptides maintained their conformation with K+ and were found in cell cytoplasm indicating K+ did not neutralize charges. K+ did not prevent oxidative stress, but protected from cell shrinkage and mitochondria hyperpolarization. dAMPs rapidly stimulated medium acidification, followed by inhibition after 1 min, and K+ prevented acidification. Membrane permeabilization occurred after 20 min, faster with WR, explaining lack of protection from blockers. Fungal death was accelerated under hypoosmotic conditions. Electrophoresis revealed protein degradation, while ultrastructural analysis of the cells showed vacuolization, indicative of cytoplasmic degradation. Thus, K+ prevented cell death by maintaining internal levels, averting activation of cell degradation process.

A leigh syndrome mutation perturbs long-range energy coupling in respiratory complex I

Respiratory complex I is a central enzyme of cellular energy metabolism that couples electron transfer with proton translocation across a biological membrane. In doing so, it powers oxidative phosphorylation that drives energy consuming processes. Mutations in complex I lead to severe neurodegenerative diseases in humans. However, the biochemical consequences of these mutations remain largely unknown. Here, we use the Escherichia coli complex I as a model to biochemically characterize the F124LMT-ND5 mutation found in patients suffering from Leigh syndrome. We show that the mutation drastically perturbs proton translocation and electron transfer activities to the same extent, despite the remarkable 140 Å distance between the mutated position and the electron transfer domain. Our molecular dynamics simulations suggest that the disease-causing mutation induces conformational changes that hamper the propagation of an electric wave through an ion-paired network essential for proton translocation. Our findings imply that malfunction of the proton translocation domain is entirely transmitted to the electron transfer domain underlining the action-at-a-distance coupling in the proton-coupled electron transfer of respiratory complex I.

Improved quality, sensory properties and nutraceutical potential of the fermented beverages fortified with freeze-dried berries and acacia honey

This study evaluates the impact of acacia honey (AH) and freeze-dried berries (raspberry (R) and blackcurrant (B) on yogurt (Y), kefir (K), and buttermilk (BM). The additives (RAH and BAH) were tested for their utility and effects on product formulation, stability, bioactive properties, and immunoreactivity. 0.5-4 % (w/v) freeze-dried fruits and 5 % (w/v) honey enhanced the functional properties of beverages by increasing antioxidant activity (10-20 times) without negatively affecting physicochemical properties. K-BAH exhibited an 80 % higher increase in total polyphenol content compared to K-RAH and other products. Additives also boosted by 1.5 log CFU/mL the growth of specific bacterial and yeast cultures in yogurt and kefir. The products met ISO microbiological standards after 28 days of storage. Safety tests indicated increased cow's alpha-amylase 2B isoform immunoreactivity starting from 1.5 % BAH-containing products. Overall, Y-RAH and Y-BAH demonstrated the highest stability, bioactivity, and sensory appeal (p < 0.05) what was confirmed through QDA and consumer trials.

Antioxidant Peptide Production Using Keratin from Feather Waste: Effect of Extraction and Thiol Blocking Method

Keratin-made biomaterials, including feathers, are considered a protein-rich bioresource due to their intrinsic properties, including biocompatibility, biodegradability, mechanical resistance, and biological abundance. Beta-keratin exists as an insoluble stringy protein due to the high presence of disulfide cross-links, and as a result, it is mechanically stable and resistant to enzymatic digestion. Because of this, it is not easily decomposed, and this has made the application of feathers difficult. In this study, after dissolving feathers in NaOH, sodium sulfide, and 2-Mercaptoethanol (2-ME), the relative molecular mass of beta-keratin was calculated. Thin-layer chromatography was also used to display proteins with lower molecular weights. The antioxidant activities of the samples were evaluated by Fe-chelating and free radical scavenging tests with 2,2-diphenyl-1-picrylhydrazyl (DPPH). To investigate the effect of blocking thiol groups on the antioxidant activity of dissolved keratin, iodoacetamide and H2O2 were used. According to the three methods-(A) sodium hydroxide, (B) sodium sulfide, and (C) urea and 2-ME-used to extract and dissolve the feathers, method C caused the least change in the chemical structure of keratin molecules. Method A destroyed the primary structure of keratin and drastically reduced its molecular mass, but method B caused a drastic increase in the molecular mass from 9.6 kDa to higher masses, due to intermolecular bonds. For the keratin molecules dissolved by method C, the Fe-chelating activity was 93.18% and free radical scavenging was 77.45%. Blocking the thiol group with iodoacetamide initially reduced the free radical scavenging activity with DPPH by 42%, but blocking it with H2O2 did not affect this activity. Also, blocking of the thiol group did not initially affect Fe-chelating activity and free radical scavenging activity. After a kinetic study of the activities, an interesting observation was that both blocking agents had negative effects on radical scavenging activity, but had positive effects on Fe-chelating activity. This indicates the complexity of the role of disulfide bonds in keratin's antioxidant behavior types. According to the observed antioxidant activities, it can be expected that beta-keratin extracted from chicken feathers is a suitable candidate for application in industrial, pharmaceutical, and health applications.

Purification, Characterization and Bioactivity of a New Homodimeric Lectin From Vicia Altissima (Fabaceae) Seeds

Vicia altissima Desf. (Fabaceae) belongs to subgenus Vicilla, section Pedunculatae. It is a perennial herb that grows in wet ravines with dense vegetation in western Mediterranean countries. The only population that exists in Spain is under critical threat of extinction. Although lectins are abundant in the seeds from several Vicias belonging to subgenus Vicilla, the presence of lectins in section Pedunculatae has not been investigated. Purification of lectins from V. altissima seeds was carried out by albumin extraction according to solubility in water and gel filtration chromatography using a Superose 12 column. SDS-PAGE and native PAGE analyses revealed single bands at 38 and 87 kDa, respectively, indicating that this protein is a homodimer. The lectin exhibited a high affinity for mannose and glucose and inhibited the proliferation of THP-1 cells. Seed lectins from Vicia species belonging to sect. Cracca in subg. Vicilla are, in general, more sensitive to inhibition by N-acetylgalactosamine than to inhibition by glucose or mannose. On the contrary, the seed lectin from V. altissima, belonging to sect. Pedunculatae, has a higher affinity for mannose and glucose than for N-acetylgalactosamine. Our results show the presence of a lectin with antiproliferative activity in the seeds from V. altissima, indicating that this lectin has potential health-promoting and diagnostic applications. These potential applications could have a positive effect on the preservation of this wild legume, which is represented in Spain by only one endangered population.

Lipid Transfer Proteins (LTPs) Partially Purified from Capsicum chinense Jacq. Seeds: Antifungal Properties and α-amylase Inhibitory Activity

In this study, we identified and partially purified antimicrobial peptides belonging to the family of lipid transfer proteins (LTPs) from Capsicum chinense seeds (UENF 1751 accession). Fractions rich in LTPs were obtained via ion exchange chromatography and subsequently purified via reverse-phase chromatography in an HPLC system. Therefore, two fractions were revealed: C1 (the nonretained fraction) and C2 (the retained fraction in ion-exchange chromatography). Fraction C1 was subjected to reverse-phase chromatography via a C18 column on an HPLC system, and ten fractions were obtained (P1-P10), all of which significantly inhibited the growth of Candida albicans, except for P4 and P9. The viability analysis of the active fractions at a concentration of 100 µg.mL-1 against C. albicans revealed that they did not exhibit fungicidal activity but rather exhibited fungistatic activity. The peptide is considered fungicidal when it results in the total loss of viable yeast cells, that is, when it causes the complete death of the fungi. When the substance only inhibits cell growth, but does not eliminate them completely, the effect is classified as fungistatic. Fractions P3, P4, P7, and P10 inhibited Tenebrio molitor larvae α-amylase. The P10 fraction presented protein bands in its electrophoretic profile with a molecular mass between 6.5 kDa and 14.2 kDa and reacted positively to an antibody produced against a protein from the LTP family bywestern blotting. The results of the analysis of amino acid residues from the P10 fraction revealed similarity between type I LTPs and type II LTPs. The ultrastructural aspects of C. albicans cells exposed to the P10 fraction were evaluated via transmission electron microscopy (TEM), with significant differences in their morphology being evident compared with those of the control. In summary, our results demonstrated the presence of LTPs in C. chinense seeds with inhibitory effects on the growth of yeasts of the genus Candida, which exhibited fungistatic effects and structural changes in C. albicans cells, in addition to exhibiting inhibitory effects on the larval insect T. molitor α-amylase.

Preliminary Purification and Partial Characterization of a Functional Bacteriocin of Lacticaseibacillus paracasei Zhang and Mining for its Gene Cluster

Bacteriocins produced by lactic acid bacteria (LAB) have good potential for use as food biopreservatives. Lacticaseibacillus paracasei Zhang (L. paracasei Zhang) is both a food use and a probiotic bacterium. This study aimed to purify and preliminary characterize the active antibacterial metabolite of L. paracasei Zhang. The cell-free supernatant of L. paracasei Zhang was collected and purified by ultrafiltration and gel filtration chromatography. The 1-3 kDa active fraction could inhibit the growth of Staphylococcus aureus but not Escherichia coli. Further antibacterial activity assays revealed its capacity to suppress various foodborne and human opportunistic pathogens (including Staphylococcus aureus, Pseudomonas fluorescens, Pseudomonas aeruginosa, Listeria monocytogenes, and Bacillus cereus), but not fungi. The antibacterial activity showed good tolerance to heat (40 to 100 °C), acid-base (pH 2-3 and pH 6-10), and digestions by a number of industrial and animal/human enzymes (such as trypsin, pepsin, α-amylase, and protease K, except papain); these desired properties make it a suitable biopreservative to be used in harsh and complex industrial production processes. The high papain sensitivity suggested a proteinaceous/peptide nature of the bioactivity. Moreover, our genomic data mining for bacteriocin through BAGEL4 revealed an area of interest encoding a complete set of putative genes required for bacteriocin production. In conclusion, our study showed that L. paracasei Zhang can produce extracellular functional antibacterial metabolite, likely a class II bacteriocin. Our preliminary extraction and characterization of the active metabolite demonstrated that it has good potential to be used as a biopreservative or an agent for suppressing gastrointestinal infections.

Molecular principles of redox-coupled sodium pumping of the ancient Rnf machinery

The Rnf complex is the primary respiratory enzyme of several anaerobic prokaryotes that transfers electrons from ferredoxin to NAD+ and pumps ions (Na+ or H+) across a membrane, powering ATP synthesis. Rnf is widespread in primordial organisms and the evolutionary predecessor of the Na+-pumping NADH-quinone oxidoreductase (Nqr). By running in reverse, Rnf uses the electrochemical ion gradient to drive ferredoxin reduction with NADH, providing low potential electrons for nitrogenases and CO2 reductases. Yet, the molecular principles that couple the long-range electron transfer to Na+ translocation remain elusive. Here, we resolve key functional states along the electron transfer pathway in the Na+-pumping Rnf complex from Acetobacterium woodii using redox-controlled cryo-electron microscopy that, in combination with biochemical functional assays and atomistic molecular simulations, provide key insight into the redox-driven Na+ pumping mechanism. We show that the reduction of the unique membrane-embedded [2Fe2S] cluster electrostatically attracts Na+, and in turn, triggers an inward/outward transition with alternating membrane access driving the Na+ pump and the reduction of NAD+. Our study unveils an ancient mechanism for redox-driven ion pumping, and provides key understanding of the fundamental principles governing energy conversion in biological systems.

Immunogenicity of an in-silico designed multi-epitope DNA vaccine encoding ROP21 and ROP29 of Toxoplasma gondii against both acute and chronic toxoplasmosis in BALB/c mice

BACKGROUND

Toxoplasma infections are highly prevalent worldwide and can cause serious complications in immunocompromised individuals and lead to congenital infections in neonates. Despite ongoing efforts to develop T. gondii vaccines, none have been developed. A potential target, the ROP21 protein catalyzes the phosphorylation of additional protein substrates and ROP29 is critical for chronic Toxoplasma gondii infection. In this study, recombinant plasmid with epitopes of ROP21 and ROP29 were used as DNA vaccine.

METHODS

An immunoinformatics approach was employed to design a multi-epitope DNA vaccine encoding T. gondii ROP21 and ROP29. The bioinformatic outputs supported the immunogenic and non-allergic nature of multi-epitope vaccine. The recombinant plasmid was transfected in HEK cells. Thereafter, the protective effect of the DNA vaccine was evaluated in BALB/c mice by way of vaccination and challenge of these mice with acute RH and chronic PRU strains of T. gondii, respectively. The immunological responses of the control and vaccinated groups were assessed using survival time, lymphocyte proliferation assays, cytokine and antibody measurements, and determination of the parasite load in the spleen with real-time PCR.

FINDINGS

Multiple epitope (ROP21 and ROP29) DNA immunization stimulated cellular and humoral immune reactions in BALB/c mice and lengthened their life following challenge. Multiple epitope proteins increased significantly the total IgG antibody concentrations, triggered increased IFN-γ cytokine production, increased the mixed IgG1/IgG2a response with a predominance of IgG2a, prolonged the survival duration and reduced the number of brain cysts. The in vivo findings indicated that the multi-epitope DNA vaccine elicited significant production of IgG antibodies (122.16 ng/ml) as well as IFN-γ (12.37 pg/ml) (p < 0.05). Moreover, a significantly reduced parasite-burden (CT: 35.62) and prolonged survival time (14 days) were observed in the immunized groups compared to the controls (p < 0.05). Low IL-4 (5.63 pg/ml) values were detected in vaccinated mice compared to the PBS control (p > 0.05).

CONCLUSIONS

We found that multiepitope protein vaccination could provide more protective immunity against chronic and acute toxoplasmosis infection compared to control.

Exploiting CotA laccase from Antarctic Bacillus sp. PAMC28748 for efficient mediator-assisted dye decolorization and ABTS regeneration

Laccases are of particular interest in addressing environmental challenges, such as the degradation of triphenylmethane (TPM) dyes, including crystal violet (CV) and Coomassie Brilliant Blue (CBB), which are commonly used in SDS-PAGE for protein visualization. However, these dyes present significant environmental concerns due to their resistance to degradation, which makes their removal from industrial wastewater a major challenge. To address this, the current study investigates the potential of a novel CotA laccase derived from Bacillus sp. PAMC28748, an Antarctic bacterial isolate, for decolorizing these stubborn dyes. The CotA gene was successfully cloned and expressed, and the enzyme demonstrated optimal activity at pH 3 and 50 °C, which favors its maximum catalytic performance. The recombinant Bacillus sp. PAMC28748 rBCLac effectively decolorized CBB without additional mediators, whereas the degradation of CV required the use of the redox mediator ABTS. With ABTS, over 90 % decolorization was achieved at a 0.35 % concentration of CV after 240 min of incubation. Further investigation through molecular docking studies revealed that hydrogen bonding and hydrophobic interactions between the enzyme and the dye molecules are critical for effective degradation, highlighting the enzyme's specific interaction mechanisms. In addition to its catalytic effectiveness, the study also demonstrated the practical potential of the rBCLac system by recovering and reusing both ABTS and rBCLac through ultracentrifugation and acetone precipitation. The process maintained over 75 % efficiency across three cycles, despite a slight decline in enzyme activity, thus showcasing the system's sustainability and reusability. These findings collectively suggest that rBCLac, isolated from an extreme Antarctic environment, holds considerable promise as a candidate for the removal of industrial wastewater containing persistent dyes, with the added potential for cost-effective and sustainable water treatment through the reuse of both the enzyme and its mediator.

Proteomic analysis of two novel peptides from the Odontobuthus doriae scorpion venom

The venom of the Odontobuthus doriae scorpion, prevalent in East Asia and Iran, has not been fully characterized. This study provides the first proteomic profile of O. doriae venom to explore its potential as a medical. 2D-PAGE analysis revealed 96 protein spots with isoelectric points from 3 to 9 and molecular weights between 6.6 to 205 kDa. Fourteen toxin fractions were isolated via HPLC, and SDS-PAGE showed seven protein bands ranging from 3.8 to 182 kDa. MALDI-TOF MS identified Peptide 1 and Peptide 2, resembling Hemoglobin beta-2 chain and Chaperonin HSP60 and suggest potential therapeutic applications for P1 and P2.

Essential role of cis-encoded mature NS3 in the genome packaging of classical swine fever virus

Classical swine fever virus (CSFV) is a member of the genus Pestivirus within the family Flaviviridae. The enveloped particles contain a plus-stranded RNA genome encoding a single large polyprotein. The processing of this polyprotein undergoes dynamic changes throughout the infection cycle. The release of mature NS3 from the polyprotein is mediated and regulated by the NS2 autoprotease and a cellular co-factor, restricting efficient cleavage to the early phases of infection. NS3 is a multifunctional viral enzyme exhibiting helicase, NTPase, and protease activities pivotal for viral replication. Hence, the release of mature NS3 fuels replication, whereas unprocessed NS2-3 precursors are vital for progeny virus production in later phases of infection. Thus far, no packaging signals have been identified for pestivirus RNA. To explore the prerequisites for particle assembly, trans-packaging experiments were conducted using CSFV subgenomes and coreless CSFV strains. Intriguingly, we discovered a significant role of mature NS3 in genome packaging, effective only when the protein is encoded by the RNA molecule itself. This finding was reinforced by employing artificially engineered CSFV strains with duplicated NS3 genes, separating uncleavable NS2-3 precursors from mature NS3 molecules. The model for NS2-3/NS3 functions in genome packaging of pestiviruses appears to be much more complicated than anticipated, involving distinct functions of the mature NS3 and its precursor molecule NS2-3. Moreover, the reliance of genome packaging on cis-encoded NS3 may act as a downstream quality control mechanism, averting the packaging of defective genomes and coordinating the encapsidation of RNA molecules before membrane acquisition.

IMPORTANCE

Pestiviruses are economically significant pathogens in livestock. Although genome organization and non-structural protein functions resemble those of other Flaviviridae genera, distinct differences can be observed. Previous studies showed that coreless CSFV strains can produce coreless virions mediated by single compensatory mutations in NS3. In this study, we could show that only RNA molecules encoding these mutations in the mature NS3 are packaged in the absence of the core protein. Unlike this selectivity, a pool of structural proteins in the host cell was readily available for packaging all CSFV genomes. Similarly, the NS2-3-4A precursor molecules required for packaging could also be provided in trans. Consequently, genome packaging in pestiviruses is governed by cis-encoded mature NS3. Reliance on cis-acting proteins restricts the acceptance of defective genomes and establishes packaging specificity regardless of RNA sequence-specific packaging signals. Understanding the role of NS3 in pestiviral genome packaging might uncover new targets for antiviral therapies.

Structural characterization of pyruvic oxime dioxygenase, a key enzyme in heterotrophic nitrification

Nitrification by heterotrophic microorganisms is an important part of the nitrogen cycle in the environment. The enzyme responsible for the core function of heterotrophic nitrification is pyruvic oxime dioxygenase (POD). POD is a non-heme, Fe(II)-dependent enzyme that catalyzes the dioxygenation of pyruvic oxime to produce pyruvate and nitrite. To analyze the catalytic mechanism of POD, the crystal structure of POD from Alcaligenes faecalis (AfPOD) was determined at 1.76 Å resolution. The enzyme is a homotetramer, and the subunit structure is homologous to those of class II aldolases, in particular, a zinc-dependent L-fuculose-1-phosphate aldolase. The active site of the subunit is located at the bottom of a cleft formed with an adjacent subunit. The iron ion at the active site is coordinated by three histidines and three water molecules in an octahedral geometry. The putative oxygen tunnel was connected between the active site and the central cavity of the tetramer. The N-terminal region of AfPOD, which is essential for catalytic activity, is disordered in the crystal. Structure prediction with AlphaFold2 combined with mutational experiments suggested that the disordered N-terminal region adopts an α-helix conformation and participates in the formation of the active site. The catalytic mechanism of the dioxygenase reaction by POD is discussed on the basis of the molecular docking model.IMPORTANCEOur knowledge of nitrification has increased considerably in recent decades with the discovery of new nitrifying microorganisms and the characterization of their biochemical processes. Some heterotrophic bacteria and fungi are known to show nitrification activities, but the molecular mechanisms have been poorly understood. Here, we performed a structural characterization of pyruvic oxime dioxygenase (POD), a key enzyme in heterotrophic nitrification that produces nitrite from ammonia using pyruvic oxime as an intermediate. Structural and enzymatic analyses revealed that POD is a unique dioxygenase with features such as an aldolase backbone, an N-terminal α-helix, and an oxygen tunnel. Our results provide insights not only into the molecular mechanisms but also into the design of specific inhibitors of heterotrophic nitrification.

Protein bL38 facilitates incorporation of uL6 during assembly of the 50S subunit in Flavobacterium johnsoniae

Previous studies of the 70S ribosome from Flavobacterium johnsoniae revealed a novel ribosomal protein, bL38, which interacts with uL6 on the 50S subunit. This 5.6 kDa protein is conserved across the Bacteroidia and encoded downstream of bL28 and bL33 in a three-gene operon. Here, we show that bL38 is critical for the growth of F. johnsoniae, and depletion of bL38 leads to accumulation of immature 50S particles, which lack uL6 and retain precursor rRNA sequences. Cryo-EM analysis of these particles reveals several putative assembly intermediates, all showing an absence of electron density for uL6 and the entire uL12 stalk region and additional densities corresponding to the unprocessed ends of the pre-23S rRNA. Extra copies of the uL6 gene can rescue the phenotypes caused by bL38 depletion, suggesting that bL38 facilitates uL6 incorporation during 50S subunit biogenesis. Cryo-EM analysis of 50S particles from this rescued strain reveals nearly twice as many intermediates, suggesting a broader and more robust assembly landscape. Differential scanning fluorimetry shows that uL6 of F. johnsoniae is intrinsically unstable, and bL38 increases the melting temperature of uL6 by 12°C. Collectively, these data suggest that bL38 binds and stabilizes uL6, thereby promoting 50S biogenesis in the Bacteroidia.

Delivery determinants of an Acinetobacter baumannii type VI secretion system bifunctional peptidoglycan hydrolase

Acinetobacter baumannii is a Gram-negative opportunistic pathogen and is a common cause of nosocomial infections. The increasing development of antibiotic resistance in this organism is a global health concern. The A. baumannii clinical isolate AB307-0294 produces a type VI secretion system (T6SS) that delivers three antibacterial effector proteins that give this strain a competitive advantage against other bacteria in polymicrobial environments. Each effector, Tse15, Tde16, and Tae17, is delivered via a non-covalent interaction with a specific T6SS VgrG protein (VgrG15, VgrG16, and VgrG17, respectively). Here we define the regions of interaction between Tae17 and its cognate delivery protein VgrG17 and identify that amino acids G1069 and W1075 in VgrG17 are essential for Tae17 delivery via the T6SS, the first time such specific delivery determinants of T6SS cargo effectors have been defined. Furthermore, we determine that the Tae17 effector is a multidomain, bifunctional, peptidoglycan-degrading enzyme that has both amidase activity, which targets the sugar-peptide bonds, and lytic transglycosylase activity, which targets the peptidoglycan sugar backbone. Moreover, we show that the Tae17 transglycosylase activity is more important than amidase activity for the killing of Escherichia coli. This study provides molecular insight into how the T6SS allows A. baumannii strains to gain dominance in polymicrobial communities and thus improve their chances of survival and transmission.IMPORTANCEWe have shown that the Acinetobacter baumannii T6SS effector Tae17 is a modular, bifunctional, peptidoglycan-degrading enzyme that has both lytic transglycosylase and amidase activities. Both activities contribute to the ability to degrade peptidoglycan, but the transglycosylase activity was more important for the killing of Escherichia coli. We have defined the specific regions of Tae17 and its cognate delivery protein VgrG17 that are necessary for the non-covalent interactions and, for the first time, identified specific amino acids essential for T6SS cargo effector delivery. This work contributes to our molecular understanding of bacterial competition strategies in polymicrobial environments and may provide a window to design new therapeutic approaches for combating infection by A. baumannii.

PET imaging of AAV9 and AAVBR1 trafficking in normal mice

Adeno-associated virus (AAV) mediated gene therapy is advancing and needs a noninvasive imaging tool to evaluate its effective targeting, biodistribution and clearance for precise use in humans. In this study, two serotypes of AAVs, AAV9-CMV-fLuc, and a brain targeting variant, AAVBR1-CMV-fLuc, are directly radiolabeled with the positron emission tomography (PET) radioisotope, 89Zr. A radiolabeling synthon, [89Zr]Zr-DFO-Bn-NCS or [89Zr]Zr-DBN, was employed for the direct radiolabeling of AAVs, which enables tracking of AAVs by PET imaging for up to 18 days post-injection. The 89Zr radiolabeled AAVs were administered to BALB/c mice via tail vein and assessed for their biodistribution at various time points up to day 18 post-injection. Imaging of AAVs was followed by ex-vivo biodistribution at day 18, or luciferase imaging at 3rd week or > 30 days post-injection. The two serotypes showed differences in their biodistribution and trafficking in mice as early as 10 min post-injection. The brain targeting serotype, [89Zr]Zr-AAVBR1-CMV-fLuc, showed significantly higher uptake in the brain as compared to [89Zr]Zr-AAV9-CMV-fLuc. The luciferase expression-based infection profile correlated with both PET imaging and ex-vivo biodistribution data. The developed methodology provides a noninvasive approach to image the pharmacokinetics of AAVs in a longitudinal manner and renders a selection of specific AAV serotypes for tissue/organ specific targeting.

Micro scale chromatography of human plasma proteins for nano LC-ESI-MS/MS

Organic precipitation of proteins with acetonitrile demonstrated complete protein recovery and improved chromatography of human plasma proteins. The separation of 25 μL of human plasma into 22 fractions on a QA SAX resin facilitated more effective protein discovery despite the limited sample size. Micro chromatography of plasma proteins over quaternary amine (QA) strong anion exchange (SAX) resins performed best, followed by diethylaminoethyl (DEAE), heparin (HEP), carboxymethyl cellulose (CMC), and propyl sulfate (PS) resins. Two independent statistical methods, Monte Carlo comparison with random MS/MS spectra and the rigorous X!TANDEM goodness of fit algorithm protein p-values corrected to false discovery rate q-values (q ≤ 0.01) agreed on at least 12,000 plasma proteins, each represented by at least three fully tryptic corrected peptide observations. There was qualitative agreement on 9393 protein/gene symbols between the linear quadrupole versus orbital ion trap but also quantitative agreement with a highly significant linear regression relationship between log observation frequency (F value 4,173, p-value 2.2e-16). The use of a QA resin showed nearly perfect replication of all the proteins that were also found using DEAE-, HEP-, CMC-, and PS-based chromatographic methods combined and together estimated the size of the size of the plasma proteome as ≥12,000 gene symbols.

Thermal degradation kinetics and purification of C-phycocyanin from thermophilic and mesophilic cyanobacteria

The natural blue colorant C-phycocyanin (C-PC) has many potential applications but its poor heat stability limits its commercial use. This study compares the production and thermal stability of C-PC from two cyanobacteria: the thermophilic Thermosynechococcus sp. TUBT-T01 and the mesophilic Synechococcus cedrorum TISTR8589. Thermosynechococcus sp. produced nearly 1.9-fold more C-PC than S. cedrorum. Batch adsorption using a chromatographic cationic ion exchange resin (Streamline Direct HST1) was used to effectively purify the C-PC. The equilibrium adsorption capacity (Qeq) of the resin for C-PC was the highest at pH 5. At this pH, the Qeq for the thermophilic C-PC was 5.5 ± 0.1 mg mL⁻¹ , whereas for the mesophilic C-PC it was 1.5 ± 0.2 mg mL⁻¹ . Purification increased the concentration of the thermophilic C-PC by 5.9-fold, and that of mesophilic C-PC by 4.2-fold. The purity ratios of the final products from the two cyanobacteria were similar at ∼2.2. At 60 °C and pH 7, the C-PC of Thermosynechococcus sp. had ∼12-times longer half-life than the mesophilic C-PC; however, the productivity of the thermophilic C-PC was comparatively low because of a low biomass productivity of Thermosynechococcus sp.

Stalled disomes marked by Hel2-dependent ubiquitin chains undergo Ubp2/Ubp3-mediated deubiquitination upon translational run-off

Stalled ribosomes cause collisions, impair protein synthesis, and generate potentially harmful truncated polypeptides. Eukaryotic cells utilize the ribosome-associated quality control (RQC) and no-go mRNA decay (NGD) pathways to resolve these problems. In yeast, the E3 ubiquitin ligase Hel2 recognizes and polyubiquitinates disomes and trisomes at the 40S ribosomal protein Rps20/uS10, thereby priming ribosomes for further steps in the RQC/NGD pathways. Recent studies have revealed high concentrations of disomes and trisomes in unstressed cells, raising the question of whether and how Hel2 selects long-term stalled disomes and trisomes. This study presents quantitative analysis of in vivo-formed Hel2•ribosome complexes and the dynamics of Hel2-dependent Rps20 ubiquitination and Ubp2/Ubp3-dependent deubiquitination. Our findings show that Hel2 occupancy progressively increases from translating monosomes to disomes and trisomes. We demonstrate that disomes and trisomes with mono- or di-ubiquitinated Rps20 resolve independently of the RQC component Slh1, while those with tri- and tetra-ubiquitinated Rps20 do not. Based on the results, we propose a model in which Hel2 translates the duration of ribosome stalling into polyubiquitin chain length. This mechanism allows for the distinction between transient and long-term stalling, providing the RQC machinery with a means to select fatally stalled ribosomes over transiently stalled ones.

Structural and Functional Analysis of Hemoglobin Binding to the Peritrophic Matrix During Blood Digestion in Aedes aegypti

The Aedes aegypti mosquito is responsible for transmitting pathogens such as the Dengue, Zika, and Chikungunya viruses. The peritrophic matrix (PM) is an extracellular chitin-rich structure that lines the midgut of arthropods, providing a crucial protective barrier for the gut epithelium against mechanical damage, ingested pathogens, and toxic substances. During blood digestion, hemoglobin is lysed, releasing free heme into the midgut lumen. Part of this heme binds strongly to the PM, mitigating its harmful effects on the mosquito epithelial cells. Our study focused on investigating the interaction dynamic between hemoglobin and the PM during blood digestion in A. aegypti. Optical microscopy was employed to observe the temporal progression of blood digestion in the A. aegypti midgut, highlighting significant morphological changes in the blood bolus. An electrophoresis analysis revealed distinct protein bands in the PM extract, some of which were associated with hemoglobin and its subunits. The presence of PM-associated hemoglobin was confirmed by amino-terminal sequencing and an immunoblot analysis using anti-hemoglobin antibodies. Furthermore, fluorescence microscopy revealed overlapping labeling between hemoglobin and chitin, suggesting an interaction between hemoglobin and PM chitin. Corroborating these results, hemoglobin showed an affinity with chitin in the chromatography and molecular docking assays, in which the hemoglobin subunits interacted with the oligosaccharide (NAG)4. Thus, hemoglobin may perform a function similar to that of peritrophins. Further experiments demonstrated the protective role of the PM against hemoglobin proteolysis during blood digestion. Overall, this study provides valuable insights into the intricate interactions between hemoglobin and the PM, enhancing our understanding of mosquito digestive physiology and potentially contributing to the development of vector control strategies.

Demystifying the functions of the mitochondrial ORFan proteins in bivalves with doubly uniparental inheritance

Strict maternal inheritance of mitochondria is known to be the rule in animals, but over 100 species across six orders of bivalves possess doubly uniparental inheritance (DUI) of mitochondria. Under DUI, two distinctive sex-specific mitogenomes coexist. In marine and freshwater mussels, each mitogenome has an additional protein-coding gene, called female- and male-specific open reading frame or forf and morf, respectively. The function(s) of the associated FORF and MORF proteins remain unknown. Herein, we show that these proteins present similar tissue expression patterns in two distantly related DUI species: MORF was only expressed in male gonads, whereas FORF was expressed in all tissues of both sexes in the marine mussel Mytilus edulis and the freshwater mussel Venustaconcha ellipsiformis. Moreover, MORF was only expressed during the reproductive season, while FORF presented no clear seasonality pattern in M. edulis. Immunocytochemistry revealed the presence of both proteins in mitochondria and acrosomes of late spermatids and mature sperm. We hypothesize that MORF has a key function in spermatogenesis, while FORF has a more general function in both sexes. We also propose that both proteins may be involved in the fertilization process. The involvement of MORF in paternal mitochondrial transmission is also discussed.

A time-saving one-step polyacrylamide gel with a colored stacking gel for SDS-PAGE and western blotting

A time-saving, one-step polyacrylamide gel preparation method enabling simultaneous preparation of separating and stacking gels was previously reported, but the boundary between the separating and stacking gels was often not well defined. As such, determining whether the gel preparation failed is difficult before SDS-PAGE is carried out. To address this issue, a one-step polyacrylamide gel preparation method was developed in which the stacking gel is colored to allow better visualization of the border between the stacking and separating gels. This new one-step method saves time and achieves comparable performance for SDS-PAGE and western blotting to that obtained with conventional gels.

Polyurethane waste valorization: A Two-Phase process using Ozonization and Rhodococcus pyridinivorans fermentation for biofertilizer production

A circular economy process has been developed to convert polyurethane waste into biofertilizing microorganisms through a sequential chemical/biological process. The chemical phase involves the complete depolymerization of polyurethane using ozone attack, generating an aqueous extract (OLE) composed of small, bioavailable molecules such as polyols, isocyanate derivatives, and carboxylic acids. The biological phase utilizes OLE for the generation of biomass with biofertilizing functional activity through Rhodococcus pyridinivorans fermentation. The metabolic-proteomic expression during the biodegradation of OLE involves the synthesis of numerous enzymes such as cutinases, hydrolases, proteases, esterases and oxidoreductases, which participate in the degradation of chemical compounds like benzene derivatives, phenols, or plastic polymers. OLE has been converted into microorganisms with biofertilizing properties, including nitrogen fixation, phytohormone production and siderophores. This process contributes to sustainability by diverting polyurethane waste from landfills, reducing the environmental impact of chemical fertilizers and promoting a more sustainable agricultural system.

Purification and Reconstitution of Ilyobacter tartaricus ATP Synthase

F-type Adenosine triphosphate (ATP) synthase is a membrane-bound macromolecular complex, which is responsible for the synthesis of ATP, the universal energy source in living cells. This enzyme uses the proton- or sodium-motive force to power ATP synthesis by a unique rotary mechanism and can also operate in reverse, ATP hydrolysis, to generate ion gradients across membranes. The F1Fo-ATP synthases from bacteria consist of eight different structural subunits, forming a complex of ~550 kDa in size. In the bacterium Ilyobacter tartaricus, the ATP synthase has the stoichiometry α3β3γδεab2c11. This chapter describes a wet-lab working protocol for the purification of several tens of milligrams of pure, heterologously (E. coli-) produced I. tartaricus Na+-driven F1Fo-ATP synthase and its subsequent efficient reconstitution into proteoliposomes. The methods are useful for a broad range of subsequent biochemical and biotechnological applications.

Synergistic Effects of Omega-3 Fatty Acids and Physical Activity on Oxidative Stress Markers and Antioxidant Mechanisms in Aged Rats

BACKGROUND

Aging induces degenerative processes in the body, contributing to the onset of various age-associated diseases that affect the population. Inadequate dietary habits and low physical activity are major contributors to increased morbidity during aging. This study aimed to investigate the combined effects of omega-3 fatty acid supplementation and physical activity on the markers of oxidative stress and antioxidant defense mechanisms in aged male Wistar rats (23-24 months).

METHODS

The rats were randomly divided into four experimental groups: a sedentary control (placebo, no exercise), a trained (placebo and moderate-intensity graded aerobic exercise; Ex), and two trained groups supplemented with low (160 mg/kg of body weight; O1 + Ex) and high (320 mg/kg of body weight; O2 + Ex) doses of omega-3 fatty acids. The biochemical and functional parameters related to sarcopenia and the markers of oxidative stress were measured in blood and gastrocnemius muscle.

RESULTS

The results demonstrated dose-dependent, synergistic effects of omega-3 fatty acid supplementation and physical activity. The higher dose (320 mg/kg of body weight) improved plasma antioxidant capacity (TEAC, +21.01%, p < 0.01) and GPx activity (+78.05%, p < 0.05) while reducing CAT activity in erythrocytes (-19.92%, p < 0.05), likely as an adaptive stress response. Combined interventions also normalized cholesterol levels, improved the functional parameters of sarcopenia (stride length, +14.82%, p < 0.001), and enhanced antioxidant protection in aged rats.

CONCLUSIONS

These findings highlight the potential of combining omega-3 fatty acid supplementation and physical activity to counteract aging-related degenerative changes. Further research is needed to elucidate the underlying mechanisms and evaluate the long-term benefits of these strategies in aging populations.

Bacillus thuringiensis Cry1A Insecticidal Toxins and Their Digests Do Not Stimulate Histamine Release from Cultured Rat Mast Cells

Public acceptance of genetically modified crops engineered with Bacillus thuringiensis (Bt) insecticidal protein genes (BT-GMCs), which confer resistance to various lepidopteran insect pests, is generally lacking. As a major concern over BT-GMCs is the allergenicity of insecticidal proteins, alleviating safety concerns should help increase public acceptance. In this study, three lepidopteran-specific Bt toxins, Cry1Aa, Cy1Ab, and Cry1Ac, were treated with simulated digestive fluids under various conditions. Western blotting using antiserum raised against individual segments (α-helices of domain I and β-sheets of domains II and III) of Cry1Aa showed that digestion produces a variety of polypeptides. In particular, the transmembrane α4-α5 of domain I, which may retain the ability to form pores, was the most resistant to digestion. Intact Cry1A toxins and these digests were then applied to RBL-2H3 cultured rat mast cells to determine whether the toxins directly induce histamine release. However, fluorescence microscopy revealed no specific binding of Cry1A toxins to RBL-2H3 cultured rat mast cells. In addition, neither the OPA method nor HPLC analysis detected significant histamine release from mast cells treated with Cry1A toxins and these digests. Our results provide important data supporting the safety of Cry1A toxins and potentially BT-GMCs.

The sequence 581Ser-610Val in the fibrinogen Aα chain is responsible for the formation of complexes between plasminogen and αC-regions of fibrin(ogen)

Objective

This study aimed to identify the binding sites for plasminogen (Pg) and its kringle-containing fragments within the αC-region of fibrin(ogen). This investigation is crucial while the conversion of fibrinogen into fibrin induces conformational changes that expose binding sites for Pg and tissue-type Pg activator (tPA), facilitating effective zymogen activation on the fibrin surface.

Methods

Two C-terminal fragments of the Aα chain ‒ 45 kDa (225Val-610Val) and 40 kDa (225Val-580Lys), were obtained through plasmin hydrolysis of human fibrinogen and subsequently characterized using MALDI TOF mass spectrometry. The interactions of Glu-Pg and Lys-Pg, as well as Pg kringle fragments (K1-3, K4, and K5), with the obtained αC truncated polypeptides were analyzed using ELISA and Western blot techniques with the use of specific antibodies.

Results

It was demonstrated that Pg and its fragments K1-3, K4, and K5 interact exclusively with the 45-kDa fragment (225Val-610Val) of the αC region of fibrinogen with high affinity in a concentration-dependent manner (Kd values for Glu-Pg = 7.10 × 10-9 M, Lys-Pg = 6.01 × 10-9 M, K1-3 = 1.08 × 10-7 M, K4 = 5.06 × 10-7 M, and K5 = 2.50 × 10-7 M). This fragment, unlike the 40-kDa polypeptide (225Val-580Lys), contains the α581Ser-610Val sequence.

Conclusions

It was shown that the sequence 581Ser-610Val of fibrinogen Aα-chain, which becomes exposed during the conversion of fibrinogen to fibrin, is essential for the formation of complexes between Pg and αC regions of fibrin(ogen), thereby contributing to the initiation and regulation of fibrinolysis.

Preparation and characterization of a mouse polyclonal antibody against the truncated ORFV113 recombinant protein of Orf virus

Orf is a contagious zoonotic disease caused by Orf virus (ORFV), posing a threat to both animal and human health. The ORFV113 gene, located in the terminal variable region of the ORFV genome, has been demonstrated as a significant virulence gene, but its function remains largely unknown. In the study, we first amplified the truncated version of the ORFV113 gene (ORFV113t) by removing its transmembrane domain at the 5' end. We then constructed the pET-32a-ORFV113t recombinant plasmid and expressed the truncated ORFV113 recombinant protein in Escherichia coli (E.coli). The purified ORFV113t fusion protein was used to immunize mice and generate a polyclonal antibody. This polyclonal antibody was subsequently used to detect the expression and subcellular localization of the ORFV113 protein. Additionally, virus neutralization test was utilized to determine the neutralizing titer of the polyclonal antibody. The results demonstrated that we successfully expressed the ORFV113t recombinant protein in a prokaryotic expression system and generated a mouse-derived polyclonal antibody targeting the ORFV113t recombinant protein with a titer of 1:204,800. This antibody exhibited specificity for detecting the ORFV113 protein expressed in both prokaryotic and eukaryotic cells. The ORFV113 protein was found to be localized in the cytoplasm of infected Lamb testis (LT) cells. Notably, the polyclonal antibody demonstrated neutralizing activity against ORFV in vitro, with a neutralizing titer of 1:32. The prepared mouse anti-ORFV113t protein polyclonal antibody can be utilized for further study on potential functions of the ORFV113 protein in viral pathogenesis.

Quinone chemistry in respiratory complex I involves protonation of a conserved aspartic acid residue

Respiratory complex I is a central metabolic enzyme coupling NADH oxidation and quinone reduction with proton translocation. Despite the knowledge of the structure of the complex, the coupling of both processes is not entirely understood. Here, we use a combination of site-directed mutagenesis, biochemical assays, and redox-induced FTIR spectroscopy to demonstrate that the quinone chemistry includes the protonation and deprotonation of a specific, conserved aspartic acid residue in the quinone binding site (D325 on subunit NuoCD in Escherichia coli). Our experimental data support a proposal derived from theoretical considerations that deprotonation of this residue is involved in triggering proton translocation in respiratory complex I.

Immunogenic potential and neutralizing ability of a heterologous version of the most abundant three-finger toxin from the coral snake Micrurus mipartitus

Background: Micrurus mipartitus is a coral snake of public health concern in Colombia. Its venom is mainly composed of three-finger toxins (3FTxs), Mipartoxin-1 being the most abundant protein partially responsible for its lethal effect. In this work, we present the production of Mipartoxin-1 in a recombinant form and evaluate its immunogenic potential. Methods: A genetic construct HisrMipartoxin-1 was cloned into the pET28a vector and heterologous expression was obtained in E. coli BL21 (DE3). The recombinant HisrMipartoxin-1 protein was extracted from inclusion bodies, refolded in vitro, and isolated by affinity and RP-HPLC chromatography. The lethal effect of HisrMipartoxin-1 was tested, and antibodies against HisrMipartoxin-1 were produced by immunization in rabbits. The antibody titers were monitored by an ELISA test. The neutralizing ability of the antibodies, against the lethal effect of native toxins and M. mipartitus venom, was also assessed. Results: HisrMipartoxin-1 was detected on SDS-PAGE, with a molecular mass of around 11 kDa. The retention time was 16.0 minutes. HisrMipartoxin-1 did not exhibit lethality in mice; however, antibodies against HisrMipartoxin-1 recognized the native toxin, the whole venom of M. mipartitus, and a 3FTx from another species within the Micrurus genus. Furthermore, antibodies against HisrMipartoxin-1 completely neutralized the lethal effect of native Mipartoxin-1 in mice but not M. mipartitus whole venom. Conclusion: These findings indicate that HisrMipartoxin-1 might be used as an immunogen to develop anticoral antivenoms or complement them. This work is the first report of the heterologous expression of 3FTx from M. mipartitus.

Supramolecular Hybrids of Proteins from Habu Snake Venom with Discrete [Pt(CN)4]2- Complex

The venom of the Habu snake Protobothrops flavoviridis (P. flavoviridis) is known to contain a diverse array of proteins and peptides, with a notable presence of phospholipase A2 (PLA2) enzymes. These PLA2 enzymes have been extensively studied for their function and molecular evolution. Nevertheless, several aspects, such as the physical properties and the self-assembly mechanism of hierarchical structure from the nanoscale to the microscale with different chemical compounds, remain poorly understood. This study aims to fill this knowledge gap by investigating the behavior of enzyme components purified from P. flavoviridis venom in the presence of anionic [Pt(CN)4]2- complexes, which have the potential for soft metallophilic interactions and interesting optical properties. The purified PLA2 isozymes were diluted in Dulbecco's phosphate buffered saline (D-PBS (-)) and combined with the anionic metal complex, resulting in the formation of microstructures several micrometers in size, which further grew to form fibrous structures. This novel approach of combining PLA2 enzymes with discrete functional metal complexes opens up exciting possibilities for designing flexible and functional supramolecular and biomolecular hybrid systems in aqueous environments. These findings shed light on the potential applications of snake venom enzymes in nanotechnology and bioengineering.

Multifunctional properties of peptides derived from black cricket (Gryllus assimilis) and effects of in vitro digestion simulation on their bioactivities

Insects are a rich source of proteins and are produced in systems that have lower environmental impact. As an alternative protein source, they can be consumed directly or used as an ingredient in other formulations. Recently, there has been growing interest in utilizing insect proteins as a substrate to obtain bioactive peptides as well as in investigating the maintenance of their biological properties under physiological conditions. This study aimed to evaluate the impact of simulated digestion on the bioactive properties of protein hydrolysates from black crickets (Gryllus assimilis). Following simulated digestion of the hydrolysate obtained through the application of Flavourzyme, the scavenging activities of ABTS and DPPH radicals, and ferric reducing antioxidant power (FRAP) increased by approximately 17 %, 246 %, and 173 %, respectively. For the hydrolysate obtained using the binary combination of Flavourzyme/Neutrase, the inhibitory activities of α-amylase and α-glucosidase after digestion were 47.87 % and 12.73 %, respectively, not significantly (p > 0.05) different from non-digested hydrolysates. The angiotensin-converting enzyme (ACE) inhibitory activity of the sample hydrolyzed with Flavourzyme/Alcalase proteases was 42.22 %, but this property was completely lost after in vitro digestion. Untargeted proteomic analysis allowed the identification of 22 peptides in the <3 kDa fraction of the digested black cricket protein. The LPPLP sequence was considered potentially bioactive for all activities tested in silico.

Interplay between CO2 and light governs carbon partitioning in Chlamydomonas reinhardtii

Increasing CO2 availability is a common practice at the industrial level to trigger biomass productivity in microalgae cultures. Still, the consequences of high CO2 availability in microalgal cells exposed to relatively high light require further investigation. Here, the photosynthetic, physiologic, and metabolic responses of the green microalga model Chlamydomonas reinhardtii were investigated in high or low CO2 availability conditions: high CO2 enabled higher biomass yields only if sufficient light energy was provided. Moreover, cells grown in high light and high CO2 availability were characterized, compared to cells grown in high light and low CO2, by a relative increase of the energy-dense triacylglycerols and decreased starch accumulation per dry weight. The photosynthetic machinery adapted to the increased carbon availability, modulating Photosystem II light-harvesting efficiency and increasing Photosystem I photochemical activity, which shifted from being acceptor side to donor side limited: cells grown at high CO2 availability were characterized by increased photosynthetic linear electron flow and by the onset of a balance between NAD(P)H oxidation and NAD(P)+ reduction. Mitochondrial respiration was also influenced by the conditions herein applied, with reduced respiration through the cytochrome pathway compensated by increased respiration through alternative pathways, demonstrating a different use of the cellular reducing power based on carbon availability. The results suggest that at high CO2 availability and high irradiance, the reducing power generated by the oxidative metabolism of photosynthates is either dissipated through alternative oxidative pathways in the mitochondria or translocated back to the chloroplasts to support carbon assimilation and energy-rich lipids accumulation.

Moojecin: The first disintegrin from Bothrops moojeni venom and its antitumor activity in acute myeloid leukemia

Disintegrins are a class of peptides found in snake venom that inhibit the activity of integrins, which are essential cell adhesion receptors in tumor progression and development. In this work, moojecin, a RGD disintegrin, was isolated from Bothrops moojeni snake venom, and its antitumor potential in acute myeloid leukemia (AML) HL-60 and THP-1 cells was characterized. The isolation was performed using a C18 reverse-phase column in two chromatographic steps, and its molecular mass is 7417.84 Da. N-terminal and de novo sequencing was performed to identify moojecin. Moojecin did not show cytotoxic or antiproliferative activity in THP-1 and HL-60 at tested concentrations, but it exhibited significant antimigratory activity in both cell lines, as well as inhibition of angiogenesis in the tube formation assay on Matrigel in a dose-dependent manner. A stronger interaction with integrin αVβ3 was shown in integrin interaction assays compared to α5β1, and the platelet aggregation assay indicated an IC50 of 5.039 μg/mL. Preliminary evaluation of disintegrin toxicity revealed no incidence of hemolysis or cytotoxic effects on peripheral blood mononuclear cells (PBMCs) across the tested concentrations. Thus, this is the first study to report the isolation, functional and structural characterization of a disintegrin from B. moojeni venom and bring a new perspective to assist in AML treatment.

In Vivo Cross-Linking Sheds Light on the Salmonella Divisome in Which PBP3 and PBP3SAL Compete for Occupancy

Bacterial cell division is orchestrated by proteins that assemble in dynamic complexes collectively known as the divisome. Essential monofunctional enzymes with glycosyltransferase or transpeptidase (TPase) activities, FtsW and FtsI respectively, engage in the synthesis of septal peptidoglycan (sPG). Enigmatically, Salmonella has two TPases that can promote cell division independently: FtsI (PBP3) and the pathogen-specific paralogue PBP3SAL. How Salmonella regulates the assembly of the sPG synthase complex with these two TPases, is unknown. Here, we characterized Salmonella division complexes in wild-type cells and isogenic mutants lacking PBP3 or PBP3SAL. The complexes were cross-linked in vivo and pulled down with antibodies recognizing each enzyme. Proteomics of the immunoprecipitates showed that PBP3 and PBP3SAL do not extensively cross-link in wild type cells, supporting the presence of independent complexes. More than 40 proteins cross-link in complexes in which these two TPases are present. Those identified with high scores include FtsA, FtsK, FtsQLB, FtsW, PBP1B, SPOR domain-containing proteins (FtsN, DedD, RlpA, DamX), amidase activators (FtsX, EnvC, NlpD) and Tol-Pal proteins. Other cross-linked proteins are the protease Prc, the elongasome TPase PBP2 and, D,D-endo- and D,D-carboxypeptidases. PBP3 and PBP3SAL localize at midcell and compete for occupying the division complex in response to environmental cues. Thus, a catalytic-dead PBP3SAL-S300A variant impairs cell division in a high osmolarity and acidic condition in which it is produced at levels exceeding those of PBP3. Salmonella may therefore exploit an 'adjustable' divisome to exchange TPases for ensuring cell division in distinct environments and, in this manner, expand its colonization capacities.

Methylglyoxal-Induced Modifications in Human Triosephosphate Isomerase: Structural and Functional Repercussions of Specific Mutations

Triosephosphate isomerase (TPI) dysfunction is a critical factor in diverse pathological conditions. Deficiencies in TPI lead to the accumulation of toxic methylglyoxal (MGO), which induces non-enzymatic post-translational modifications, thus compromising protein stability and leading to misfolding. This study investigates how specific TPI mutations (E104D, N16D, and C217K) affect the enzyme's structural stability when exposed to its substrate glyceraldehyde 3-phosphate (G3P) and MGO. We employed circular dichroism, intrinsic fluorescence, native gel electrophoresis, and Western blotting to assess the structural alterations and aggregation propensity of these TPI mutants. Our findings indicate that these mutations markedly increase TPI's susceptibility to MGO-induced damage, leading to accelerated loss of enzymatic activity and enhanced protein aggregation. Additionally, we observed the formation of MGO-induced adducts, such as argpyrimidine (ARGp), that contribute to enzyme inactivation and aggregation. Importantly, the application of MGO-scavenging molecules partially mitigated these deleterious effects, highlighting potential therapeutic strategies to counteract MGO-induced damage in TPI-related disorders.

New Catalytic Residues and Catalytic Mechanism of the RNase T1 Family

The ribonuclease T1 family, including RNase Po1 secreted by Pleurotus ostreatus, exhibits antitumor activity. Here, we resolved the Po1/guanosine-3'-monophosphate complex (3'GMP) structure at 1.75 Å. Structure comparison and fragment molecular orbital (FMO) calculation between the apo form and the Po1/3'GMP complex identified Phe38, Phe40, and Glu42 as the key binding residues. Two types of the RNase/3'GMP complex in RNasePo1 and RNase T1 were homologous to Po1, and FMO calculations elucidated that the biprotonated histidine on the β3 sheet (His36) on the β3 sheet and deprotonated Glu54 on the β4 sheet were advantageous to RNase activity. Moreover, tyrosine (Tyr34) on the β3 sheet was elucidated as a crucial catalytic residues. Mutation of Tyr34 with phenylalanine decreased RNase activity and diminished antitumor efficacy compared to that in the wild type. This suggests the importance of RNase activity in antitumor mechanisms.

Molecular and functional characterization of ILYS-5, a major invertebrate lysozyme of Caenorhabditis elegans

To overcome bacterial invasion and infection, animals have evolved various antimicrobial effectors such as antimicrobial peptides and lysozymes. Although C. elegans is exposed to a variety of microbes due to its bacterivorous lifestyle, previous work on the components of its immune system mainly based on the description of transcriptional changes during bacterial challenges. Very few effector components of its immune system have been characterized so far. To investigate the role of lysozymes in terms of antibacterial defense and digestion, we studied a member of the widely neglected family of C. elegans invertebrate lysozymes (ILYS). We focused on the so far virtually undescribed ILYS-5, which we purified from protein extracts of C. elegans tracing its peptidoglycan-degrading activity and localized the tissue expression of the gene in vivo using a translational reporter construct. We recombinantly synthesized ILYS-5 and determined the physicochemical activity optimum and the antibacterial spectrum of a lysozyme from C. elegans for the first time. With an activity optimum at low ionic strength (≤100 mM) and at acidic pH (≤ pH 4.0), ILYS-5 is likely to be involved in killing and digestion of bacteria within acidified phagolysosomes and acidic regions of the gut, presumably secreted by lysosome-like vesicles. This notion is supported by potent activity against various live Gram-positive and Gram-negative bacteria. Notably, members of the natural associated microbiome of C. elegans are substantially less susceptible to ILYS-5. Ablation of the ilys-5 gene resulted in reduction of lifespan and fertility when cultured on the standard food bacterium Escherichia coli OP50, whereas exposure of the ilys-5 knock-out mutant to the host-associated bacterium Pseudomonas lurida MYb11 did not have a clear effect. These findings indicate a role of ILYS-5 in immunity and nutrition and a co-evolved adaptation of host and bacteria to the mutualistic nature of their interaction.

A missense mutation in the barley Xan-h gene encoding the Mg-chelatase subunit I leads to a viable pale green line with reduced daily transpiration rate

KEY MESSAGE

The barley mutant xan-h.chli-1 shows phenotypic features, such as reduced leaf chlorophyll content and daily transpiration rate, typical of wild barley accessions and landraces adapted to arid climatic conditions. The pale green trait, i.e. reduced chlorophyll content, has been shown to increase the efficiency of photosynthesis and biomass accumulation when photosynthetic microorganisms and tobacco plants are cultivated at high densities. Here, we assess the effects of reducing leaf chlorophyll content in barley by altering the chlorophyll biosynthesis pathway (CBP). To this end, we have isolated and characterised the pale green barley mutant xan-h.chli-1, which carries a missense mutation in the Xan-h gene for subunit I of Mg-chelatase (HvCHLI), the first enzyme in the CBP. Intriguingly, xan-h.chli-1 is the only known viable homozygous mutant at the Xan-h locus in barley. The Arg298Lys amino-acid substitution in the ATP-binding cleft causes a slight decrease in HvCHLI protein abundance and a marked reduction in Mg-chelatase activity. Under controlled growth conditions, mutant plants display reduced accumulation of antenna and photosystem core subunits, together with reduced photosystem II yield relative to wild-type under moderate illumination, and consistently higher than wild-type levels at high light intensities. Moreover, the reduced content of leaf chlorophyll is associated with a stable reduction in daily transpiration rate, and slight decreases in total biomass accumulation and water-use efficiency, reminiscent of phenotypic features of wild barley accessions and landraces that thrive under arid climatic conditions.