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Biology subjects

Carrasco, C.

Publications and source records attributed to Carrasco, C..

5 recordsLinked to original sources

Deep learning-guided identification of bacteriophage receptor-binding protein candidates for foodborne pathogen detection

Foodborne pathogens including Salmonella spp., Escherichia coli and Listeria monocytogenes cause an estimated 600 million illnesses annually. Yet conventional detection methods remain slow, costly, or insufficiently specific for routine food safety surveillance. Phage receptor-binding proteins (RBPs) are attractive recognition elements for biosensors, but their extensive sequence diversity limits reliable computational identification. Here, we present a systematic open-source computational pipeline for identifying and structurally characterising high-confidence RBP candidates from phage genomes targeting these three priority pathogens. The pipeline integrates four stages: deep learning-based RBP prediction, protein structure prediction, structural homology validation, and exploratory molecular docking. Applied to a quality-controlled dataset of 247 complete phage genomes retrieved from the National Center for Biotechnology Information Nucleotide database (31,752 total protein sequences), PhageRBPdetect, built on the ESM-2 protein language model, identified 653 high-confidence RBP candidates. Foldseek structural homology validation against PDB100 confirmed 13 candidates with a structural match probability of 1.0 to known phage adsorption proteins, spanning four structural archetypes. ESMFold-predicted structures showed strong confidence, with a mean model confidence score of 0.89 and a 90.2% prediction success rate. Exploratory rigid-body docking identified YDV08491.1, an E. coli-targeting candidate, as having the most energetically favourable predicted interaction, with a predicted binding energy of -132.3 kcal/mol against OmpF, supporting experimental prioritisation. These candidates structural diversity and predicted host specificity support their future development as phage-based biosensors and biocontrol tools, and this reproducible, accessible pipeline offers a transferable strategy for prioritising RBP candidates in downstream functional studies, pending experimental validation. Author SummaryFoodborne bacterial infections cause an estimated 600 million illnesses every year worldwide, with Salmonella, Escherichia coli, and Listeria monocytogenes among the most significant contributors. Detecting these pathogens quickly and specifically in food supply chains remains a major challenge for global food safety. Bacteriophages viruses that infect bacteria use surface proteins called receptor-binding proteins (RBPs) to recognize their bacterial hosts with remarkable precision, making RBPs promising building blocks for pathogen-specific biosensors. However, the huge sequence diversity of RBPs across phage genomes has made it difficult to reliably identify good candidates computationally. We built an open-source pipeline that combines deep learning, protein structure prediction, and molecular docking to screen phage genomes for high-confidence RBP candidates. Applied to 247 phage genomes targeting the three pathogens above, our pipeline flagged 653 candidate RBPs, of which 13 showed strong structural similarity to known phage adsorption proteins. One candidate, targeting E. coli, showed a particularly strong predicted binding interaction with a bacterial surface protein, making it a priority target for experimental testing. This pipeline gives researchers a reproducible, publicly available strategy for prioritizing phage proteins toward the development of biosensors and biocontrol tools for food safety.

bioinformatics↗

RPA directly stimulates Mer3/HFM1 helicase processivity to ensure normal crossover formation in meiosis

Meiotic crossover formation is critical for generating viable gametes and enhancing genetic diversity. The helicase Mer3 (HFM1 in humans) is a highly conserved factor essential for promoting crossovers and ensuring their proper distribution. Here, we identify replication protein A (RPA) as a direct interactor of budding yeast Mer3. We demonstrate that this interaction is conserved between human HFM1 and RPA. Cross-linking mass spectrometry and structural modelling with AlphaFold2 reveal a conserved and specific Mer3-RPA interface. Single-molecule magnetic tweezers assays demonstrate that direct RPA interaction is required for Mer3 helicase processivity under conditions of low DNA tension. Consistently, a mer3 mutant deficient in RPA binding exhibit reduced crossover frequencies and accumulate unresolved recombination intermediates during budding yeast meiosis. Via genome-wide localisation experiments, we link this effect to a weakened recruitment to double-strand break sites of the mer3 mutant. Our findings provide mechanistic insights into coordination of meiotic recombination by the Mer3 helicase through interactions with the canonical DNA repair machinery, highlighting a conserved mechanism underlying crossover control during sexual reproduction.

biochemistry↗

Neurons, Muscles, and Venom: Identifying Drivers of Cephalopod Predation

Venom plays a central role in the predatory ecology of coleoid cephalopods (octopuses, squids, and cuttlefish), yet the mechanisms governing venom release from the posterior salivary gland (PSG) are unknown. Using a multimodal approach combining X-ray micro-histotomography, histological stainings, in situ hybridization, comparative phylogenetics, and ex vivo imaging across multiple coleoid species, we characterize the structural and neuronal regulatory organization of the PSG. We verified that the gland comprises two distinct tubular systems: secretory tubules specialized for venom production and smooth-striated tubules positioned to facilitate venom transport toward the beak for injection into its prey. Molecular localization of filamentous and -actin confirms a circular smooth muscle layer surrounding the tubules. Mapping of six neuronal markers, including neurofilament (NF-H), synapsin, and muscle-type nicotinic acetylcholine receptors, reveals dense and stereotyped neural innervation closely associated with the muscular compartments. Comparative phylogenetic analyses of cys-loop ligand-gated ion channel sequences indicate a predominancy of excitatory acetylcholine- and dopamine-gated receptors in coleoid venom glands, implicating potential molecular agents involved in neural control of venom release. Consistent with neural regulation, ex vivo stimulation of the PSG elicits calcium signaling throughout the gland. Together, our results reveal a conserved venom gland structure among octopuses, squids, and cuttlefish, with a spatially distinct neuromuscular tissue organization indicating venom production and release sites modulated by a network of neuronal agents. This work provides a mechanistic framework into venom gland organization and molecular regulation of venom release in one of the oldest venomous lineages.

neuroscience↗

Inhibition of the sodium-dependent HCO3 -transporter SLC4A4, produces a cystic fibrosis-like airway disease phenotype.

Bicarbonate secretion is a fundamental process involved in maintaining acid-base homeostasis. Disruption of bicarbonate entry into airway lumen, as has been observed in cystic fibrosis, produces several defects in lung function due to thick mucus accumulation. Bicarbonate is critical for correct mucin deployment and there is increasing interest in understanding its role in airway physiology, particularly in the initiation of lung disease in children affected by cystic fibrosis, in the absence of detectable bacterial infection. The current model of anion secretion in mammalian airways consists of CFTR and TMEM16A as apical anion exit channels, with limited capacity for bicarbonate transport compared to chloride. However, both channels can couple to SLC26A4 anion exchanger to maximise bicarbonate secretion. Nevertheless, current models lack any details about the identity of the basolateral protein(s) responsible for bicarbonate uptake into airway epithelial cells. We report herein that the electrogenic, sodium-dependent, bicarbonate cotransporter, SLC4A4, is expressed in the basolateral membrane of human and mouse airways, and that its pharmacological inhibition or genetic silencing reduces bicarbonate secretion. In fully differentiated primary human airway cells, SLC4A4 inhibition induced an acidification of the airways surface liquid and markedly reduced the capacity of cells to recover from an acid load. Studies in the Slc4a4-null mice revealed a previously unreported lung phenotype, characterized by mucus accumulation and reduced mucociliary clearance. Collectively, our results demonstrate that the reduction of SLC4A4 function induced a CF-like phenotype, even when chloride secretion remained intact, highlighting the important role SLC4A4 plays in bicarbonate secretion and mammalian airway function.

physiology↗

Bulk and single-molecule analysis of a novel DNA2-like helicase-nuclease reveals a single-stranded DNA looping motor

DNA2 is an essential enzyme involved in DNA replication and repair in eukaryotes. In a search for homologues of this protein, we identified and characterised Geobacillus stearothermophilus Bad, a novel bacterial DNA helicase-nuclease with similarity to human DNA2. We show that Bad contains an Fe-S cluster and identify four cysteine residues that are likely to co-ordinate the cluster by analogy to DNA2. The purified enzyme specifically recognises ss-dsDNA junctions and possesses ssDNA-dependent ATPase, ssDNA binding, ssDNA endonuclease, 5 to 3 ssDNA translocase and 5 to 3 helicase activity. Single molecule analysis reveals that Bad is a highly processive DNA motor capable of moving along DNA for distances of more than 4 kbp at a rate of [~]200 base pairs per second at room temperature. Interestingly, as reported for the homologous human and yeast DNA2 proteins, the DNA unwinding activity of Bad is cryptic and can be unmasked by inactivating the intrinsic nuclease activity. Strikingly, our experiments also show that the enzyme loops DNA while translocating, which is an emerging feature of highly processive DNA unwinding enzymes. The bacterial Bad enzymes will provide an excellent model system for understanding the biochemical properties of DNA2-like helicase-nucleases and DNA looping motor proteins in general.

biochemistry↗