Successful allogeneic fecal microbiota transplantation for severe diversion colitis: a case report.

Ileostomy diverts the flow of feces, which can result in malnutrition in the distal part of the intestine. The diversity of the gut microbiota consequently decreases, ultimately leading to intestinal dysbiosis and dysfunction. This condition can readily result in diversion colitis (DC). Potential treatment strategies include interventions targeting the gut microbiota. In this case study, we effectively treated a patient with severe DC by ileostomy and allogeneic fecal microbiota transplantation (FMT). A 69-year-old man presented with a perforated malignant tumor in the descending colon and an iliac abscess. He underwent laparoscopic radical sigmoid colon tumor resection and prophylactic ileostomy. Follow-up colonoscopy 3 months postoperatively revealed diffuse intestinal mucosal congestion and edema along with granular inflammatory follicular hyperplasia, leading to a diagnosis of severe DC. After two rounds of allogeneic FMT, both the intestinal mucosal bleeding and edema significantly improved, as did the diversity of the gut microbiota. The positive outcome of allogeneic FMT in this case highlights the potential advantages that this procedure can offer patients with DC. However, few studies have focused on allogeneic FMT, and more in-depth research is needed to gain a better understanding.

Analysis of Potential Risks in Abnormal Physical Development Due to Dietary Habits in Preschool Children.

Background: The prevalence of abnormal physical development in preschool children is often linked to their dietary habits, necessitating a comprehensive investigation. Understanding the intricacies of these habits is crucial for formulating targeted interventions to enhance the overall health and well-being of this vulnerable population. Objective: This study aims to explore the dietary habits of preschool children in Shijiazhuang and evaluate their impact on abnormal physical development. The primary objective is to identify key dietary issues, particularly focusing on picky eating, and assess their association with undernutrition and obesity in this age group. Methods: Utilizing a stratified sampling approach, the study involves preschool children and their caregivers from various kindergartens in Shijiazhuang. On-site medical examinations are conducted to measure height and weight and calculate body mass index (BMI). Additionally, parents were surveyed to gather information on the general aspects and dietary habits of their children. Binary logistic regression analysis was employed to ascertain the correlation between picky eating and the risk of undernutrition and obesity. Results: The findings indicate that approximately 70% of preschool children maintain a normal BMI, while 16.67% experience undernutrition, and 13.33% face issues of being overweight or obese. Picky eating emerges as the predominant dietary habit issue, affecting 51.33% of the participants. Binary logistic regression analysis identifies picky eating as a significant risk factor for undernutrition and obesity among children. Conclusions: Picky eating stands out as the primary dietary habit concern for preschool children, concurrently posing a substantial risk for abnormal physical development. Urgent measures are warranted to rectify children's suboptimal dietary habits, elevate nutritional standards, and foster their overall health and development. These findings underscore the imperative need for interventions targeting dietary improvement in preschoolers, contributing to improving their well-being and long-term health outcomes.

FedCut: A Spectral Analysis Framework for Reliable Detection of Byzantine Colluders.

This paper proposes a general spectral analysis framework that thwarts a security risk in federated Learning caused by groups of malicious Byzantine attackers or colluders, who conspire to upload vicious model updates to severely debase global model performances. The proposed framework delineates the strong consistency and temporal coherence between Byzantine colluders' model updates from a spectral analysis lens, and, formulates the detection of Byzantine misbehaviours as a community detection problem in weighted graphs. The modified normalized graph cut is then utilized to discern attackers from benign participants. Moreover, the Spectral heuristics is adopted to make the detection robust against various attacks. The proposed Byzantine colluder resilient method, i.e., FedCut, is guaranteed to converge with bounded errors. Extensive experimental results under a variety of settings justify the superiority of FedCut, which demonstrates extremely robust model accuracy (MA) under various attacks. It was shown that FedCut's averaged MA is 2.1% to 16.5% better than that of the state of the art Byzantine-resilient methods. In terms of the worst-case model accuracy (MA), FedCut is 17.6% to 69.5% better than these methods.

Studies on the in vitro mechanism and in vivo therapeutic effect of the antimicrobial peptide ACP5 against Trichophyton mentagrophytes.

Trichophyton mentagrophytes is a zoophilic dermatophyte that can cause dermatophytosis in humans and animals. Antimicrobial peptides (AMPs) are considered as a promising agent to overcome the drug-resistance of T. mentagrophytes. Our findings suggest that cationic antimicrobial peptide (ACP5) not only possesses stronger activity against T. mentagrophytes than fluconazole, but also shows lower toxicity to L929 mouse fibroblast cells than terbinafine. Notably, its resistance development rate after resistance induction was lower than terbinafine. The present study aimed to evaluate the fungicidal mechanism of ACP5 in vitro and its potential to treat dermatophyte infections in vivo. ACP5 at 1 ×MIC completely inhibited T. mentagrophytes spore germination in vitro. ACP5 severely disrupts the mycelial morphology, leading to mycelial rupture. Mechanistically, ACP5 induces excessive ROS production, damaging the integrity of the cell membrane and decreasing the mitochondrial membrane potential, causing irreversible damage in T. mentagrophytes. Furthermore, 1% ACP5 showed similar efficacy to the commercially available drug 1% terbinafine in a guinea pig dermatophytosis model, and the complete eradication of T. mentagrophytes from the skin by ACP5 was verified by tissue section observation. These results indicate that ACP5 is a promising candidate for the development of new agent to combat dermatophyte resistance.

Characterization of the Zinc Uptake Repressor (Zur) from Acinetobacter baumannii.

Bacterial cells tightly regulate the intracellular concentrations of essential transition metal ions by deploying a panel of metal-regulated transcriptional repressors and activators that bind to operator-promoter regions upstream of regulated genes. Like other zinc uptake regulator (Zur) proteins, Acinetobacter baumannii Zur represses transcription of its regulon when ZnII is replete and binds more weakly to DNA when ZnII is limiting. Previous studies established that Zur proteins are homodimeric and harbor at least two metal sites per protomer or four per dimer. CdII X-ray absorption spectroscopy (XAS) of the Cd2Zn2 AbZur metalloderivative with CdII bound to the allosteric sites reveals a S(N/O)3 first coordination shell. Site-directed mutagenesis suggests that H89 and C100 from the N-terminal DNA binding domain and H107 and E122 from the C-terminal dimerization domain comprise the regulatory metal site. KZn for this allosteric site is 6.0 (±2.2) × 1012 M-1 with a functional "division of labor" among the four metal ligands. N-terminal domain ligands H89 and C100 contribute far more to KZn than H107 and E122, while C100S AbZur uniquely fails to bind to DNA tightly as measured by an in vitro transcription assay. The heterotropic allosteric coupling free energy, ΔGc, is negative, consistent with a higher KZn for the AbZur-DNA complex and defining a bioavailable ZnII set-point of ≈6 × 10-14 M. Small-angle X-ray scattering (SAXS) experiments reveal that only the wild-type Zn homodimer undergoes allosteric switching, while the C100S AbZur fails to switch. These data collectively suggest that switching to a high affinity DNA-binding conformation involves a rotation/translation of one protomer relative to the other in a way that is dependent on the integrity of C100. We place these findings in the context of other Zur proteins and Fur family repressors more broadly.

Case Report: Fecal Microbiota Transplantation for the Treatment of Generalized Eczema Occurring After COVID-19 Vaccination.

Adverse skin reactions caused by the COVID-19 vaccine have attracted considerable attention. As we all know, the development mechanism of some skin diseases is related to the gut and skin microbiome. A 78-year-old male patient who received the COVID-19 vaccine developed generalized eczema with multiple dense black patches over the body, a widespread rash, erosion, and scabs on his limbs, as well as facial edema. The patient experienced recurrent flare-ups after conventional treatment, but then recovered well without recurrence after undergoing three fecal microbial transplantation (FMT) treatments. This rare case is reported for the first time in this study. This report demonstrates the possible potential of FMT in targeting refractory skin diseases, such as eczema, as well as diseases associated with gut microbiota disturbance after vaccination.

Changes in the shape and function of the fetal heart of pre- and gestational diabetes mothers.

BACKGROUND: Hyperglycemia during pregnancy can affect fetal heart in many ways, including causing cardiac malformation, leading to hypertrophic cardiomyopathy and cardiac dysfunction. Echocardiographic evaluation can assist identify alterations in heart structure, morphology and function, enabling prompt monitoring and management. However, according to earlier research, the cardiac alterations are modest in hyperglycemic mothers' fetuses, and might not be detectable using conventional methods and it is also unclear whether these changes are related to the metabolism of mothers. Fetal Heart Quantification (Fetal HQ) can assess ventricular geometry and function more sensitively and thoroughly, and identify sub-clinical cardiac dysfunction. The purpose of this study was to evaluate fetal heart by Fetal HQ in fetuses of hyperglycemic mothers who either had pre-gestational or gestational diabetes and to correlate them with maternal metabolic indices. METHODS: The fetuses of 25 gestational age-matched control mothers, 48 women with gestational diabetes mellitus (GDM), and 11 women with diabetes mellitus (DM) were included in the prospective case-control research. Using fetal echocardiography and speckle tracking echocardiography (STE), the heart of the fetus was evaluated. Differences in the groups' anthropometric, metabolic, and cardiac parameters were examined. It was assessed whether maternal features, prenatal glucose, lipids, and maternal hemoglobin A1c (HbA1c) correlated with fetal cardiac parameters. RESULTS: The LV EDV and ESV were significantly higher in the GDM group as compared to the DM group (p < 0.05). The GSI% was significantly lower in the GDM group compared with the control (p < 0.05). The LV SV and CO of the GDM group were both significantly higher compared with the DM group (p < 0.05). There was a significant decrease in RV FS for segments 1-7 in GDM fetuses compared to the control (p < 0.05) and for segments 5-10 compared to DM (p < 0.05). Fetal cardiac morphology and function indices correlate with maternal pregestational weight, BMI, early pregnancy fast glucose, lipids, and glycemic control levels. CONCLUSIONS: Fetuses exposed to gestational diabetes have altered heart morphology and function that is linked to maternal metabolic parameters, which presents a special indication for performing geometry and function cardiac assessment. Fetal HQ can be employed to evaluate the fetal cardiac shape and function in fetuses exposed to gestational diabetes.

Surgical strategies and outcomes for myocardial bridges coexisting with other cardiac conditions.

BACKGROUND: Myocardial bridges are congenital coronary artery anomalies. There are still many controversies surrounding surgical treatment strategies for myocardial bridges combined with other heart disorders. The purpose of this study was to evaluate the surgical treatment strategies and outcomes in patients with these conditions. METHODS: Between March 2004 and October 2021, our institution witnessed 77 patients diagnosed with myocardial bridging who underwent surgical intervention. According to the myocardial bridge and combined heart disorder, four groups were identified: 1. isolated LAD supra-arterial myotomy group, 2. LAD CABG and(or not) myotomy  group, 3. LAD supra-arterial myotomy and grafting of other branches group, and 4. LAD supra-arterial myotomy and other cardiac surgery group. The perioperative outcomes, symptoms, life quality, mortality, and major adverse cardiac events (MACEs) were analyzed. RESULTS: There were no deaths during hospitalization and no rethoractomy for postoperative bleeding or major adverse cardiac events (MACEs). The follow-up period ranged from 2 months to 199.2 months (55.61 ± 10.21) months, the 10-year cumulative survival rates for the four groups of patients were 95.0%, 100%, 100% and 74.1%, and the 10-year freedom rates from the MACEs were 83.9%, 92.0%, 87.5% and 76.2%, respectively. CONCLUSIONS: Supra-arterial myotomy is preferred in patients with isolated myocardial bridge, and acceptable results can be achieved by choosing supra-arterial myotomy in combination with CABG or other cardiac surgery simultaneously for patients with myocardial bridges and other heart disorders.

Solution Structure of Poly(UG) RNA.

Poly(UG) or "pUG" RNAs are UG or GU dinucleotide repeat sequences which are highly abundant in eukaryotes. Post-transcriptional addition of pUGs to RNA 3' ends marks mRNAs as vectors for gene silencing in C. elegans. We previously determined the crystal structure of pUG RNA bound to the ligand N-methyl mesoporphyrin IX (NMM), but the structure of free pUG RNA is unknown. Here we report the solution structure of the free pUG RNA (GU)12, as determined by nuclear magnetic resonance spectroscopy and small and wide-angle x-ray scattering (NMR-SAXS-WAXS). The low complexity sequence and 4-fold symmetry of the structure result in overlapped NMR signals that complicate chemical shift assignment. We therefore utilized single site-specific deoxyribose modifications which did not perturb the structure and introduced well-resolved methylene signals that are easily identified in NMR spectra. The solution structure ensemble has a root mean squared deviation (RMSD) of 0.62 Å and is a compact, left-handed quadruplex with a Z-form backbone, or "pUG fold." Overall, the structure agrees with the crystal structure of (GU)12 bound to NMM, indicating the pUG fold is unaltered by docking of the NMM ligand. The solution structure reveals conformational details that could not be resolved by x-ray crystallography, which explain how the pUG fold can form within longer RNAs.

Associations of ApoE Polymorphisms with Postoperative Atrial Fibrillation and Cardiac Injury in Patients with Coronary Artery Bypass Graft Surgery.

Genetic factors may be involved in postoperative atrial fibrillation (PoAF) development and cardiac injury. However, the associations of the apolipoprotein E (ApoE) gene polymorphisms with PoAF and cardiac injury after coronary artery bypass graft surgery (CABG) remain unclear.We recruited 150 patients with CABG, comprising 92 and 58 cases for the ApoE4 and ApoE3 groups, respectively, and analyzed PoAF incidence and the levels of cardiac biomarkers, including N-terminal prohormone of brain natriuretic peptide, cardiac troponin T (cTnT), and cardiac troponin I (cTnI). The linear regression model or logistic regression analysis was applied to investigate the associations of ApoE gene polymorphisms with PoAF and biomarkers for cardiac injury.A total of 58 (38.7%) patients with CABG developed PoAF, with 40 and 18 cases in the ApoE4 and ApoE3 groups (43.5% versus 31.0%, P < 0.05), respectively. Logistic regression analysis revealed that the ApoE4 allele was an independent risk factor for PoAF (OR = 3.340, P = 0.001), while the ApoE3 allele was a protective factor for the PoAF (OR = 0.841, P = 0.043). Patients carrying the ApoE4 allele had higher levels of cTnT and cTnI than those carrying the ApoE3 allele. ApoE3 was a protective factor for cardiac injury (ß = -0.220, P = 0.001), whereas ApoE4 was a risk factor for cTnI (ß = 0.335, P = 0.015).Our study reveals that the ApoE allele contributes to the occurrence of PoAF and severity of cardiac injury in an allele-dependent manner, with the ApoE4 allele increasing the risk and the ApoE3 allele reducing the risk.

Responses of the microbial community and the production of extracellular polymeric substances to sulfamethazine shocks in a novel two-stage biological contact oxidation system.

Introduction: The biological contact oxidation reactor is an effective technology for the treatment of antibiotic wastewater, but there has been little research investigating its performance on the sulfamethazine wastewater treatment. Methods: In this study, a novel two-stage biological contact oxidation reactor was used for the first time to explore the impact of sulfamethazine (SMZ) on the performance, microbial community, extracellular polymeric substances (EPS), and antibiotic-resistant genes (ARGs). Results: The chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) removal efficiencies kept stable at 86.93% and 83.97% with 0.1-1 mg/L SMZ addition and were inhibited at 3 mg/L SMZ. The presence of SMZ could affect the production and chemical composition of EPS in the biofilm, especially for the pronounced increase in TB-PN yield in response against the threat of SMZ. Metagenomics sequencing demonstrated that SMZ could impact on the microbial community, a high abundance of Candidatus_Promineofilum, unclassified_c__Anaerolineae, and unclassified_c__Betaproteobacteria were positively correlated to SMZ, especially for Candidatus_Promineofilum. Discussion: Candidatus_Promineofilum not only had the ability of EPS secretion, but also was significantly associated with the primary SMZ resistance genes of sul1 and sul2, which developed resistance against SMZ pressure through the mechanism of targeted gene changes, further provided a useful and easy-implement technology for sulfamethazine wastewater treatment.

Direct observation of tRNA-chaperoned folding of a dynamic mRNA ensemble.

T-box riboswitches are multi-domain noncoding RNAs that surveil individual amino acid availabilities in most Gram-positive bacteria. T-boxes directly bind specific tRNAs, query their aminoacylation status to detect starvation, and feedback control the transcription or translation of downstream amino-acid metabolic genes. Most T-boxes rapidly recruit their cognate tRNA ligands through an intricate three-way stem I-stem II-tRNA interaction, whose establishment is not understood. Using single-molecule FRET, SAXS, and time-resolved fluorescence, we find that the free T-box RNA assumes a broad distribution of open, semi-open, and closed conformations that only slowly interconvert. tRNA directly binds all three conformers with distinct kinetics, triggers nearly instantaneous collapses of the open conformations, and returns the T-box RNA to their pre-binding conformations upon dissociation. This scissors-like dynamic behavior is enabled by a hinge-like pseudoknot domain which poises the T-box for rapid tRNA-induced domain closure. This study reveals tRNA-chaperoned folding of flexible, multi-domain mRNAs through a Venus flytrap-like mechanism.

Developmental Process and Symmetry of Fetal Sulci in the Mesial Area Assessed by Ultrasound: A Cohort Study in Chinese Population.

OBJECTIVE: We aimed to investigate the progression of cortical development in Chinese population and to determine the rate of isolated asymmetric cortical development. We also explored the outcomes of these fetuses and determined whether cortical asymmetry represents normal individual physiological variation. METHODS: Our observational cohort study included 456 healthy singleton pregnant women who visited Peking University First Hospital between September 2020 and December 2021. We evaluated the progression and symmetry of the parieto-occipital sulcus, calcarine sulcus, and cingulate sulcus using a scoring system during routine fetal ultrasound examinations. The outcomes of the included fetuses after birth were assessed using the Ages and Stages Questionnaire, Third Edition (ASQ-3). RESULTS: The median gestational ages at which the parieto-occipital, calcarine, and cingulate sulci reached grade 1 were 22, 22, and 26 weeks, respectively. Among 456 included fetuses, 426 showed symmetric cortical development and 30 showed asymmetric cortical development during ultrasound examination. Fetuses with asymmetric cortical development underwent 'catch-up growth' and developed to the same grade in 2-6 weeks. All fetuses with symmetric or asymmetric cortical development had normal neurodevelopment after birth according to ASQ-3 assessment. CONCLUSION: The gestational age at which the parieto-occipital, calcarine, and cingulate sulci can be detected using ultrasound varies in different studies. Racial differences may be present in cortical development. Normal fetuses may physiologically have mildly asymmetric cortical development in the mesial area.

Architectural basis for cylindrical self-assembly governing Plk4-mediated centriole duplication in human cells.

Proper organization of intracellular assemblies is fundamental for efficient promotion of biochemical processes and optimal assembly functionality. Although advances in imaging technologies have shed light on how the centrosome is organized, how its constituent proteins are coherently architected to elicit downstream events remains poorly understood. Using multidisciplinary approaches, we showed that two long coiled-coil proteins, Cep63 and Cep152, form a heterotetrameric building block that undergoes a stepwise formation into higher molecular weight complexes, ultimately generating a cylindrical architecture around a centriole. Mutants defective in Cep63•Cep152 heterotetramer formation displayed crippled pericentriolar Cep152 organization, polo-like kinase 4 (Plk4) relocalization to the procentriole assembly site, and Plk4-mediated centriole duplication. Given that the organization of pericentriolar materials (PCM) is evolutionarily conserved, this work could serve as a model for investigating the structure and function of PCM in other species, while offering a new direction in probing the organizational defects of PCM-related human diseases.

Crystal structure of Escherichia coli thiamine pyrophosphate-sensing riboswitch in the apo state.

The thiamine pyrophosphate (TPP)-sensing riboswitch is one of the earliest discovered and most widespread riboswitches. Numerous structural studies have been reported for this riboswitch bound with various ligands. However, the ligand-free (apo) structure remains unknown. Here, we report a 3.1 Å resolution crystal structure of Escherichia coli TPP riboswitch in the apo state, which exhibits an extended, Y-shaped conformation further supported by small-angle X-ray scattering data and driven molecular dynamics simulations. The loss of ligand interactions results in helical uncoiling of P5 and disruption of the key tertiary interaction between the sensory domains. Opening of the aptamer propagates to the gene-regulatory P1 helix and generates the key conformational flexibility needed for the switching behavior. Much of the ligand-binding site at the three-way junction is unaltered, thereby maintaining a partially preformed pocket. Together, these results paint a dynamic picture of the ligand-induced conformational changes in TPP riboswitches that confer conditional gene regulation.

Surgical intervention of myocardial bridge combined coronary artery disease: could a combination of supra-arterial myotomy and CABG be a better option?

BACKGROUND: The treatment of coronary artery disease combined with severe atherosclerotic stenosis proximal to a left anterior descending artery myocardial bridge (LAD-MB) is still controversial. This study aimed to analyze the outcomes of surgical intervention in patients with severe atherosclerotic stenosis proximal to a LAD-MB. METHODS: We retrospectively reviewed all patients with coronary artery disease combined with severe atherosclerotic stenosis proximal to the LAD-MB. The enrolled criteria were systolic compression of LAD more than or equal to 50% and atherosclerotic stenosis proximal to the LAD-MB more than or equal to 70%. All patients suffered from anginal symptoms refractory to medical therapy. All patients received supra-arterial myotomy and coronary artery bypass grafting (CABG) procedures. Clinical characteristics, intraoperative findings, and postoperative outcomes were evaluated. RESULTS: Between 2004 and 2021, sixteen patients underwent supra-arterial myotomy and CABG procedure. The compression and length of LAD-MB were 63 ± 17.9% and 25.9 ± 16.3 mm, respectively. Of the 16 patients, one patient had a LAD-MB and proximal coronary stenosis, and 15 patients had LAD-MBs and multivessel lesions. All patients survived and recovered uneventfully without in-hospital mortality or severe complications. The median transfusion amount of red blood cells in the operation was 2 units, and no patients required unplanned reoperation for bleeding. The average length of intensive care unit stay was 2.74 days. Fifteen patients were followed up for 6-146.1 months (mean 45.3 ± 42.9 months). One patient had a recurrence of angina pectoris one year after surgery, and 14 patients had no symptoms of myocardial ischemia during the follow-up period. Significant improvement in symptoms and quality of life using the Seattle Angina Questionnaire assessment was observed in all five categories after surgery (p < 0.01). CONCLUSIONS: Based on the results, supra-arterial myotomy and concomitant bypass surgery may be a better option for the treatment of LAD-MB combined with severe proximal stenosis.

The role of SMAD signaling in hypertrophic obstructive cardiomyopathy: an immunohistopathological study in pediatric and adult patients.

Hypertrophic obstructive cardiomyopathy (HOCM) can bring a high risk of sudden cardiac death in young people. It is particularly urgent to understand the development and mechanism of HOCM to prevent unsafe incidents. Here, the comparison between pediatric and adult patients with HOCM has been performed to uncover the signaling mechanism regulating pathological process through histopathological analysis and immunohistochemical analysis. We found SMAD proteins played an important role during myocardial fibrosis for HOCM patients. In patients with HOCM, Masson and HE staining showed that myocardial cells were diffusely hypertrophied with obvious disorganized myocardial fiber alignment, and myocardial tissue was more damaged and collagen fibers increased significantly, which come early in childhood. Increased expressions of SMAD2 and SMAD3 contributed to myocardial fibrosis in patients with HOCM, which happened early in childhood and continued through adulthood. In addition, decreased expression of SMAD7 was closely related to collagen deposition, which negatively expedited fibrotic responses in patients with HOCM. Our study indicated that the abnormal regulation of SMAD signaling pathway can lead to severe myocardial fibrosis in childhood and its fibrogenic effects persist into adulthood, which is a crucial factor in causing sudden cardiac death and heart failure in HOCM patients.

Visualizing RNA conformational and architectural heterogeneity in solution.

RNA flexibility is reflected in its heterogeneous conformation. Through direct visualization using atomic force microscopy (AFM) and the adenosylcobalamin riboswitch aptamer domain as an example, we show that a single RNA sequence folds into conformationally and architecturally heterogeneous structures under near-physiological solution conditions. Recapitulated 3D topological structures from AFM molecular surfaces reveal that all conformers share the same secondary structural elements. Only a population-weighted cohort, not any single conformer, including the crystal structure, can account for the ensemble behaviors observed by small-angle X-ray scattering (SAXS). All conformers except one are functionally active in terms of ligand binding. Our findings provide direct visual evidence that the sequence-structure relationship of RNA under physiologically relevant solution conditions is more complex than the one-to-one relationship for well-structured proteins. The direct visualization of conformational and architectural ensembles at the single-molecule level in solution may suggest new approaches to RNA structural analyses.

Structure of Helicobacter pylori dihydroneopterin aldolase suggests a fragment-based strategy for isozyme-specific inhibitor design.

Dihydroneopterin aldolase (DHNA) is essential for folate biosynthesis in microorganisms. Without a counterpart in mammals, DHNA is an attractive target for antimicrobial agents. Helicobacter pylori infection occurs in human stomach of over 50% of the world population, but first-line therapies for the infection are facing rapidly increasing resistance. Novel antibiotics are urgently needed, toward which structural information on potential targets is critical. We have determined the crystal structure of H. pylori DHNA (HpDHNA) in complex with a pterin molecule (HpDHNA:Pterin) at 1.49-Å resolution. The HpDHNA:Pterin complex forms a tetramer in crystal. The tetramer is also observed in solution by dynamic light scattering and confirmed by small-angle X-ray scattering. To date, all but one reported DHNA structures are octameric complexes. As the only exception, ligand-free Mycobacterium tuberculosis DHNA (apo-MtDHNA) forms a tetramer in crystal, but its active sites are only partially formed. In contrast, the tetrameric HpDHNA:Pterin complex has well-formed active sites. Each active site accommodates one pterin molecule, but the exit of active site is blocked by two amino acid residues exhibiting a contact distance of 5.2 â€‹Å. In contrast, the corresponding contact distance in Staphylococcus aureus DHNA (SaDHNA) is twice the size, ranging from 9.8 to 10.5 â€‹Å, for ligand-free enzyme, the substrate complex, the product complex, and an inhibitor complex. This large contact distance indicates that the active site of SaDHNA is wide open. We propose that this isozyme-specific contact distance (ISCD) is a characteristic feature of DHNA active site. Comparative analysis of HpDHNA and SaDHNA structures suggests a fragment-based strategy for the development of isozyme-specific inhibitors.