Machine-Learning-Assisted Design of Deep Eutectic Solvents Based on Uncovered Hydrogen Bond Patterns.

Non-ionic deep eutectic solvents (DESs) are non-ionic designer solvents with various applications in catalysis, extraction, carbon capture, and pharmaceuticals. However, discovering new DES candidates is challenging due to a lack of efficient tools that accurately predict DES formation. The search for DES relies heavily on intuition or trial-and-error processes, leading to low success rates or missed opportunities. Recognizing that hydrogen bonds (HBs) play a central role in DES formation, we aim to identify HB features that distinguish DES from non-DES systems and use them to develop machine learning (ML) models to discover new DES systems. We first analyze the HB properties of 38 known DES and 111 known non-DES systems using their molecular dynamics (MD) simulation trajectories. The analysis reveals that DES systems have two unique features compared to non-DES systems: The DESs have ① more imbalance between the numbers of the two intra-component HBs and ② more and stronger inter-component HBs. Based on these results, we develop 30 ML models using ten algorithms and three types of HB-based descriptors. The model performance is first benchmarked using the average and minimal receiver operating characteristic (ROC)-area under the curve (AUC) values. We also analyze the importance of individual features in the models, and the results are consistent with the simulation-based statistical analysis. Finally, we validate the models using the experimental data of 34 systems. The extra trees forest model outperforms the other models in the validation, with an ROC-AUC of 0.88. Our work illustrates the importance of HBs in DES formation and shows the potential of ML in discovering new DESs.

The role of trimethylation on histone H3 lysine 27 (H3K27me3) in temozolomide resistance of glioma.

Temozolomide (TMZ) is the first-line chemotherapeutic agent for malignant glioma, but its resistance limited the benefits of the treated patients. In this study, the role and significance of trimethylation of histone H3 lysine 27 (H3K27me3) in TMZ resistance were investigated. Data from twenty advanced glioma patients were collected, and their pathological samples were analyzed for H3K27me3 levels. TMZ sensitivity was compared between glioma cells U87 and TMZ-resistant cells U87TR, with H3K27me3 levels determined in both cells. The effects of H3K27me3 demethylases inhibitor GSK-J4, combined with TMZ, were assessed on the proliferation and migration of U87TR cells. The results indicated that a high level of H3K27me3 predicts longer disease free survival (DFS) and overall survival (OS) in glioma patients receiving TMZ treatment. The H3K27me3 level was lower in U87TR cells compared to U87 cells. GSK-J4 increased the H3K27me3 level in U87TR cells and decreased their resistance to TMZ. In summary, this study identified a novel marker of TMZ resistance in glioma and provided a new strategy to address this challenge. These findings are significant for improving the clinical treatment of glioma in the future.

A newly identified secretory phospholipase A2 group XIIA homolog (LcPLA2XIIA) in Larimichthys crocea exhibits antimicrobial and antitumor activities.

The phospholipase A2 (PLA2) superfamily has attracted increasing attention in recent years due to the multiple physiological and pathological functions exerted by its members. Up to date, the knowledge about the biological role of PLA2XIIA subfamily members remains limited. In this study, a new member of PLA2XIIA subfamily, LcPLA2XIIA, was characterized in large yellow croaker. Different from most members of the PLA2 superfamily with positive charge, LcPLA2XIIA encodes an anionic protein, which is similar to other members of PLA2XIIA subfamily. LcPLA2XIIA is highly expressed in the intestine, and afterwards, it is up-regulated after with Pseudomonas plecoglossicida or Staphylococcus aureus. LcPLA2XIIA exhibits strong inhibitory activity against these two bacteria. The results indicate that LcPLA2XIIA plays an important role in the antimicrobial immune responses of large yellow croaker. LcPLA2XIIA displays strong binding activity to all the tested bacteria. It specifically interacts with LTA, a unique component on the surface of Gram-positive bacteria. It also significantly promotes bacterial agglutination in the presence of Ca2+. These findings reveal that the binding and agglutinating abilities of LcPLA2XIIA to bacteria contribute greatly to its antibacterial activity. In addition, LcPLA2XIIA significantly inhibits the proliferation of infectious hematopoietic necrosis virus instead of recombinant human adenovirus type 5. It also suppresses the growth of human colorectal adenocarcinoma cells by inducing apoptosis, but it has no obvious inhibitory effect on the growth of epithelioma papulosum cyprinid cells. This study provides new insights into the antibacterial activity, and the mechanism of LcPLA2XIIA in large yellow croaker, and antiviral and antitumor functions of PLA2XIIA subfamily members.

Quantitative expression of LNAPL pollutant concentrations in capillary zone by coupling multiple environmental factors based on random forest algorithm.

The capillary zone plays a crucial role in migration and transformation of pollutants. Light nonaqueous liquids (LNAPLs) have become the main organic pollutant in soil and groundwater environments. However, few studies have focused on the concentration distribution characteristics and quantitative expression of LNAPL pollutants within capillary zone. In this study, we conducted a sandbox-migration experiment using diesel oil as a typical LNAPL pollutant, with the capillary zone of silty sand as the research object. The variation characteristics of LNAPL pollutants (total petroleum hydrocarbon) concentration and environmental factors (moisture content, electrical conductivity, pH, and oxidationreduction potential) were essentially consistent at different locations with the same height. These characteristics differed within range of 10.0-50.0 cm and above 60.0 cm from groundwater. A model for quantitative expression of concentrations was constructed by coupling multiple environmental factors of 968 sets-7744 data via random forest algorithm. The goodness of fit (R2) for both training and test sets was greater than 0.90, and the mean absolute percentage error (MAPE) was less than 16.00 %. The absolute values of relative errors in predicting concentrations at characteristic points were less than 15.00 %. The constructed model can accurately and quantitatively express and predict concentrations in capillary zone.

Multiple Resonance Quasi-fluorescence from BN-Doped Aromatic Compounds Modified with "Naphthalene" Units Approaches the BT.2020 Green Light Standard.

Creating fluorophores that meet the Broadcast Service Television 2020 (BT.2020) standard is a significant achievement. In this paper, we present an innovative strategy that could revolutionize the development of high-performance narrowband fluorophores for ultra-high-definition displays. Our approach combines classic multi-resonance BN-doped fragments with naphthalene, creating two novel narrowband bright green quasi-fluorescent emitters, NT-2B and NT-3B. When tested in dilute toluene, these molecules exhibit emission peaks at 510 and 511 nm with extremely narrow FWHM values of 15 and 14 nm, respectively. Both molecules also demonstrate conventional fluorescence properties with high photoluminescence quantum yields (PLQYs) of up to 85%. Notably, OLEDs containing NT-2B achieve a peak EQE of approximately 30% and at a doping concentration of 5 wt.%, OLEDs based on NT-2B achieve a CIEy value of roughly 0.75, closely matching the BT.2020 standard.

The Efficacy of Modified Ilizarov Distraction-Tension Device on Limb Wound Difficult to Cover with Skin Flaps.

INTRODUCTION: Closure of complex limb wounds poses challenges and requires innovative approaches. This research aimed to evaluate the effectiveness of a modified distraction-tension device using Ilizarov external fixation for wound closure in challenging cases. METHODS: A retrospective analysis was conducted on 43 patients with extremity wounds that were difficult to cover with skin flaps between January 2019 and December 2022. Tension-relieving traction was applied using the Ilizarovexternal fixator apparatus, tailored to individual wound characteristics. Three types of wire-pin connections were used in this study. The distraction begins on the third postoperative day, with a speed of 0.5mm/d. Clinical wound healing scores were evaluated at 5 and 30 days postoperatively. Complications were documented following the Paley classification system. RESULTS: Traction using modified Ilizarovexternal fixation promoted a significant reduction in wound size. The mean traction period was 11.2 ± 7.3 days, and the mean healing duration was 17.0 ± 3.7 days. The clinical wound healing score improved from 3.7 ± 2.9 at 5 days to 1.7 ± 0.7 at 30 days postoperatively (p < 0.05). Complications were minimal, with no significant obstacles or sequelae observed. Direct closure healing was achieved in 21 cases, skin graft healing in 13 cases, and suture healing in 9 cases. No recurrences were reported. Using Paley's classified complications, there were 17 problems, 9 obstacles, and 0 sequelae. CONCLUSION: The Ilizarov tension-relieving traction shows promise in facilitating wound closure that is challenging to manage with skin flaps. The modified three types of pin-skin connection configuration could satisfy various types of wound closure.

Effect of temperature fluctuations during frozen storage on ice crystal distribution and quality of tilapia (Oreochromis mossambicus).

The study constructed a model of temperature fluctuation (TF, -20 °C âˆ¼ -10 °C) during frozen status to build a link between the tilapia fillets muscle of ice crystal morphology, moisture distribution, protein oxidation index and the edible quality. When TF treatment more than 3 times, the brightness, color and hardness of frozen tilapia fillets decreased significantly, and the cooking loss and thawing loss increased significantly. The free and unconjugated water in frozen fish fillets exceeded 97 % and did not change much after 9 times TF. The K and TVB-N values were within the safety standards (K < 60 %, TVB-N < 30 mg N/100 g). The ice crystals in the tissues were significantly increased. Protein carbonyls and Ca2+-ATPase were significantly reduced, and secondary structures were irregular. Network correlation analysis showed that ice crystal morphology was significantly correlated with the color, texture and protein oxidation index of frozen tilapia fillets. The results would provide theoretical approach for the transportation and sales of tilapia industrial enterprises.

Pirarubicin combined with TLR3 or TLR4 agonists enhances anti-tumor efficiency.

BACKGROUND: Triple-negative breast cancer (TNBC) is prone to relapse due to the lack of effective therapeutic targets. Macrophages are the most abundant immune cells in the tumor microenvironment (TME) of breast cancer. Targeting the cross-talk between macrophages and cancer cells provides a more efficient strategy for anti-tumor therapy. Toll-like receptors (TLRs) are important players involved in macrophage activation, and TLR agonists are known to play roles in cancer therapy. However, the combination strategy of TLR agonists with chemotherapy drugs is still not well characterized. METHODS: RT-PCR and Western blot were used to detect the expression of TLRs. The communication between breast cancer cells and macrophages were determined by co-culture in vitro. Tumor cells proliferation and migration were investigated by MTT assay and scratch wound assay. The effects of drug combinations and toxic side effects were assessed by immunohistochemistry and Hematoxylin & Eosin staining. RESULTS: Expression of TLR3 and TLR4 were lower in breast tumor tissues compared with adjacent normal tissues. Patients with higher TLR3 or TLR4 expression levels had a better prognosis than those with lower expression levels. TLR3/4 expression was significantly inhibited when breast cancer cells MDA-MB-231 and E0771 were conditioned-cultured with macrophages in vitro and was also inhibited by pirarubicin (THP). However, the combination of TLR agonists and THP could reverse this response and inhibit the proliferation and migration of breast cancer cells. Additionally, this combination significantly reduced the tumor volume and weight in the murine model, increased the expression of TLR3/4 in mouse breast tumors. CONCLUSIONS: Our results provide new ideas for the combination strategy of THP with TLR agonists which improves prognosis of breast cancer.

Multiphysical field and multiobjective mathematical modeling of grain-oilseed storage: Current status and future trends.

Storage is an important process involved in the postharvest treatment of grain-oilseed and is necessary for maintaining high quality and ensuring the long-term supply of these commodities in the food industry. Proper storage practices help prevent spoilage, maintain nutritional value, and preserve marketable quality. It is of great interest for storage to investigate flow, heat and mass transfer processes, and quality change for optimizing the operation parameters and ensuring the quality of grain-oilseed. This review discusses the mathematical models developed and applied to describe the physical field, biological field, and quality change during the storage of grain-oilseed. The advantages, drawbacks, and industrial relevance of the existing mathematical models were also critically evaluated, and an organic system was constructed by correlating them. Finally, the future research trends of the mathematical models toward the development of multifield coupling models based on biological fields to control quality were presented to provide a reference for further directions on the application of numerical simulations in this area. Meanwhile, artificial intelligence (AI) can greatly enhance our understanding of the coupling relationships within grain-oilseed storage. AI's strengths in both qualitative and quantitative analysis, as well as its effectiveness, make it an invaluable tool for this purpose.

The nonradiative decay mechanism of dinuclear iridium complexes: a density functional theory study.

Dinuclear metal complexes are a promising class of compounds applicable to photoluminescence and catalysis. However, an understanding of the mechanism of the nonradiative decay process of dinuclear metal complexes remains very limited. Herein, the mechanism of the nonradiative decay process of dinuclear iridium(III) complexes (D1 and D2) and their mononuclear iridium(III) complex (M1) is elucidated by using density functional theory (DFT). Our results reveal that the nonradiative decay process occurs on a weak Ir-N bond and therefore results in metal-centered triplet excited (3MC) states. The deactivation pathways connecting the Franck-Condon region and the minimum energy seam of crossing (MESX) were further identified to be the determining step, which is the thermal deactivation pathways of 3MLCT → TS → 3MC→ MESX. The smaller energy barrier from the T1 minimum to the MESX state for D1 (9.48 kcal mol-1) and D2 (8.64 kcal mol-1) relative to that for M1 (10.95 kcal mol-1) plays a key role in observed weak emissions of D1 and D2 in the red region compared to that of M1. Moreover, by introducing the electron-withdrawing Cl atom at the para- or meta-position of the 2-phenylpyrimidine (ppd) moiety, a large energy barrier between the 3MC state and the T1 minimum is obtained. Our work not only provides the possibility of the nonradiative decay process of dinuclear iridium(III) materials, but also paves a promising way for reducing the nonradiative process and developing saturated efficient red dinuclear iridium(III) materials for broader potential application.

Brain organoid maturation and implantation integration based on electrical signals input.

INTRODUCTION: Brain organoids are believed to be able to regenerate impaired neural circuits and reinstate brain functionality. The neuronal activity of organoids is considered a crucial factor for restoring host function after implantation. However, the optimal stage of brain organoid post-transplantation has not yet been established. External electrical signal plays a crucial role in the physiology and development of a majority of human tissues. However, whether electrical input modulates the development of brain organoids, making them ideal transplant donors, is elusive. METHODS: Bioelectricity was input into cortical organoids by electrical stimulation (ES) with a multi-electrode array (MEA) to obtain a better-transplanted candidate with better viability and maturity, realizing structural-functional integration with the host brain. RESULTS: We found that electrical stimulation facilitated the differentiation and maturation of organoids, displaying well-defined cortical plates and robust functional electrophysiology, which was probably mediated via the pathway of calcium-calmodulin (CaM) dependent protein kinase II (CAMK II)-protein kinase A (PKA)-cyclic-AMP response binding protein (pCREB). The ES-pretreated D40 organoids displayed superior cell viability and higher cell maturity, and were selected to transplant into the damaged primary sensory cortex (S1) of host. The enhanced maturation was exhibited within grafts after transplantation, including synapses and complex functional activities. Moreover, structural-functional integration between grafts and host was observed, conducive to strengthening functional connectivity and restoring the function of the host injury. CONCLUSION: Our findings supported that electrical stimulation could promote the development of cortical organoids. ES-pretreated organoids were better-transplanted donors for strengthening connectivity between grafts and host. Our work presented a new physical approach to regulating organoids, potentially providing a novel translational strategy for functional recovery after brain injury. In the future, the development of 3D flexible electrodes is anticipated to overcome the drawbacks of 2D planar MEA, promisingly achieving multimodal stimulation and long-term recordings of brain organoids.

Decoding the genomic enigma: Approaches to studying extrachromosomal circular DNA.

Extrachromosomal circular DNA (eccDNA), a pervasive yet enigmatic component of the eukaryotic genome, exists autonomously from its chromosomal counterparts. Ubiquitous in eukaryotes, eccDNA plays a critical role in the orchestration of cellular processes and the etiology of diseases, particularly cancers. However, the full scope of its influence on health and disease remains elusive, presenting a rich vein of research yet to be mined. Unraveling the complexities of eccDNA necessitates a distillation of methodologies - from biogenesis to functional analysis - a landscape we overview in this study with precision and clarity. Here, we systematically outline cutting-edge methodologies from high-throughput sequencing and bioinformatics to experimental validations, showcasing the intricate world of eccDNAs. We combed through a treasure trove of auxiliary research resources and analytical tools. Moreover, we chart a course for future inquiry, illuminating the horizon with potential groundbreaking strategies for designing eccDNA research projects and pioneering new methodological frontiers.

Three patients with new mutations in the EPCAM variant gene for congenital tufting enteropathy and a mutation review in China: a case report.

Background: Congenital tufting enteropathy (CTE) is a rare cause of intractable congenital diarrhea in children, always resulting in parenteral nutrition (PN) dependency. We aimed to report novel mutations in Chinese patients and to illustrate the clinical, histopathological, and molecular features of CTE in China. Case Description: We report three cases of CTE diagnosed with whole-exome sequencing (WES) and MOC31 [a monoclonal antibody of epithelial cell adhesion molecule (EPCAM)] immunohistochemistry. The main manifestations in the three patients were watery diarrhea and growth retardation. Upper endoscopy in three patients revealed villous atrophy of the duodenal mucosa. Histological examination revealed villus abnormalities and two patients with focal tufting. All of the three patients revealed a complete absence of EPCAM expression through MOC31 immunohistochemistry. Five novel mutations, including c.319delG, c.505_507delGAG, c.491+1G>C, c.60del (p.F20Lfs*17), and c.353G>A, in EPCAM were identified through molecular analysis. In our review, there were 18 different mutations in 11 patients from nine studies, with 12 mutations reported only once. In China, 73% of the patients were compound heterozygotes, and most of the pathogenic variants were in exon 3. All patients presented with congenital diarrhea and needed PN because of growth retardation, even when diarrhea was improved. Of the 11 patients, 3 (27%) died. Conclusions: CTE is rare and fatal, and lacks characteristic changes during endoscopy. Patients with CTE require early diagnosis via histological examination and genetic detection to improve survival.

Facile synthesis of ATTM@ZIF-8 modified pullulan hydrogels for enhanced adsorption of Congo red and malachite green.

Efficient capture of dyes from wastewater is of great importance for environmental remediation. Yet constructing adsorbents with satisfactory adsorption efficiency and low cost remains a major challenge. This work reports a simple and scalable method for the fabrication of functionalized porous pullulan hydrogel adsorbent decorated with ATTM@ZIF-8 for the adsorption of congo red (CR) and malachite green (MG). The embedding of ammonium tetrathiomolybdate (ATTM) into the ZIF-8 nanoclusters offered additional adsorption sites and enlarged the pore size of the resulting ATTM@ZIF-8. The homogeneous dispersion of the nanoparticles in the three-dimensional network of polysaccharide gels prevents their agglomeration and thus improves the affinity for dye molecules. The resulting adsorbent AZP-20 at optimized composite ratios exhibits high activity, selectivity, interference resistance, reusability and cytocompatibility in dye adsorption applications, and possesses high removal rate of dye in real water systems. Batch experiments demonstrated that the adsorption rate of AZP-20 for MG and CR was 1645.28 mg g-1 and 680.33 mg g-1, and would be influenced by pH conditions. Adsorption kinetics followed pseudo-second-order model. Adsorption isotherms followed Langmuir model for MG and Freundlich model for CR. The adsorption of dye molecules primarily relied on electrostatic interaction (MG) and π-π stacking interaction (CR). Conclusively, the prepared AZPs adsorbent illuminated good application prospects in the treatment of complex component dye wastewater.

Single-cell transcriptomics reveals tumor microenvironment remodeling in hepatocellular carcinoma with varying tumor subclonal complexity.

Introduction: The complexity of tumor cell subclonal structure has been extensively investigated in hepatocellular carcinoma. However, the role of subclonal complexity in reshaping the tumor microenvironment (TME) remains poorly understood. Methods: We integrated single-cell transcriptome sequencing data from four independent HCC cohorts, involving 30 samples, to decode the associations between tumor subclonal complexity and the TME. We proposed a robust metric to accurately quantify the degree of subclonal complexity for each sample based on discrete copy number variations (CNVs) profiles. Results: We found that tumor cells in the high-complexity group originated from the cell lineage with FGB overexpression and exhibited high levels of transcription factors associated with poor survival. In contrast, tumor cells in low-complexity patients showed activation of more hallmark signaling pathways, more active cell-cell communications within the TME and a higher immune activation status. Additionally, cytokines signaling activity analysis suggested a link between HMGB1 expressed by a specific endothelial subtype and T cell proliferation. Discussion: Our study sheds light on the intricate relationship between the complexity of subclonal structure and the TME, offering novel insights into potential therapeutic targets for HCC.

Whether hypoxia tolerance improved after short-term fasting is closely related to phylogeny but not to foraging mode in freshwater fish species.

The combined stresses of fasting and hypoxia are common events during the life history of freshwater fish species. Hypoxia tolerance is vital for survival in aquatic environments, which requires organisms to down-regulate their maintenance energetic expenditure while simultaneously preserving physiological features such as oxygen supply capacity under conditions of food deprivation. Generally, infrequent-feeding species who commonly experience food shortages might evolve more adaptive strategies to cope with food deprivation than frequent-feeding species. Thus, the present study aimed to test whether the response of hypoxia tolerance in fish to short-term fasting (2 weeks) varied with different foraging modes. Fasting resulted in similar decreases in maintenance energetic expenditure and similar decreases in Pcrit and Ploe between fishes with different foraging modes, whereas it resulted in decreased oxygen supply capacity only in frequent-feeding fishes. Furthermore, independent of foraging mode, fasting decreased Pcrit and Ploe in all Cypriniformes and Siluriformes species but not in Perciformes species. The mechanism for decreased Pcrit and Ploe in Cypriniformes and Siluriformes species is at least partially due to the downregulated metabolic demand and/or the maintenance of a high oxygen supply capacity while fasting. The present study found that the effect of fasting on hypoxia tolerance depends upon phylogeny in freshwater fish species. The information acquired in the present study is highly valuable in aquaculture industries and can be used for species conservation in the field.

Caspase-11 signaling promotes damage to hippocampal CA3 to enhance cognitive dysfunction in infection.

BACKGROUND: Cognitive dysfunction caused by infection frequently emerges as a complication in sepsis survivor patients. However, a comprehensive understanding of its pathogenesis remains elusive. METHODS: In our in vivo experiments, an animal model of endotoxemia was employed, utilizing the Novel Object Recognition Test and Morris Water Maze Test to assess cognitive function. Various techniques, including immunofluorescent staining, Western blotting, blood‒brain barrier permeability assessment, Limulus Amebocyte Lysate (LAL) assay, and Proximity-ligation assay, were employed to identify brain pathological injury and neuroinflammation. To discern the role of Caspase-11 (Casp11) in hematopoietic or non-hematopoietic cells in endotoxemia-induced cognitive decline, bone marrow chimeras were generated through bone marrow transplantation (BMT) using wild-type (WT) and Casp11-deficient mice. In vitro studies involved treating BV2 cells with E. coli-derived outer membrane vesicles to mimic in vivo conditions. RESULTS: Our findings indicate that the deficiency of Casp11-GSDMD signaling pathways reverses infection-induced cognitive dysfunction. Moreover, cognitive dysfunction can be ameliorated by blocking the IL-1 effect. Mechanistically, the absence of Casp11 signaling significantly mitigated blood‒brain barrier leakage, microglial activation, and synaptic damage in the hippocampal CA3 region, ultimately leading to improved cognitive function. CONCLUSION: This study unveils the crucial contribution of Casp11 and GSDMD to cognitive impairments and spatial memory loss in a murine sepsis model. Targeting Casp11 signaling emerges as a promising strategy for preventing or treating cognitive dysfunction in patients with severe infections.

A Review on the Influence of Crystal Facets on the Product Selectivity of CO2RR over Cu Metal Catalysts.

The electrocatalytic carbon dioxide reduction reaction (ECRR) is promising in converting environmentally harmful CO2 into useful chemicals, but the large-scale application of this technology is seriously limited by its low efficiency and selectivity. Cu-based electrocatalysts displayed attractive ability in converting CO2 to multiple products, and the product selectivity can be manipulated through various approaches. Among them, exposing specific crystal facets through crystal facet engineering has been proven to be highly effective in obtaining specific products and has attracted numerous researchers. However, to our knowledge, few reports have systematically summarized the relationship between the crystal facet control of Cu catalysts and the catalytic products. This review begins by outlining the general mechanism of CO2 electrocatalytic reduction on Cu-based catalysts, and then summarizes the preferences of low-index and high-index Cu facets regarding product selectivity and delves into the synergistic effects between facets (including different Cu facets and interactions between Cu and non-Cu facets) and their impact on CO2 reduction reaction (CO2RR). In addition, the study of the recently developed Cu single-atom catalysts in ECRR was also introduced. Finally, we provide an outlook on the development of high-performance Cu-based catalysts for applications in CO2RR. The purpose of this review is to provide a clear vein and meaningful guidance for the following studies over the crystal facet control of Cu-based electrocatalysts.

Mechanistic insights into lanthipeptide modification by a distinct subclass of LanKC enzyme that forms dimers.

Naturally occurring lanthipeptides, peptides post-translationally modified by various enzymes, hold significant promise as antibiotics. Despite extensive biochemical and structural studies, the events preceding peptide modification remain poorly understood. Here, we identify a distinct subclass of lanthionine synthetase KC (LanKC) enzymes with distinct structural and functional characteristics. We show that PneKC, a member of this subclass, forms a dimer and possesses GTPase activity. Through three cryo-EM structures of PneKC, we illustrate different stages of peptide PneA binding, from initial recognition to full binding. Our structures show the kinase domain complexed with the PneA core peptide and GTPγS, a phosphate-bound lyase domain, and an unconventional cyclase domain. The leader peptide of PneA interact with a gate loop, transitioning from an extended to a helical conformation. We identify a dimerization hot spot and propose a "negative cooperativity" mechanism toggling the enzyme between tense and relaxed conformation. Additionally, we identify an important salt bridge in the cyclase domain, differing from those in in conventional cyclase domains. These residues are highly conserved in the LanKC subclass and are part of two signature motifs. These results unveil potential differences in lanthipeptide modification enzymes assembly and deepen our understanding of allostery in these multifunctional enzymes.