Structure and thiazide inhibition mechanism of the human Na-Cl cotransporter.

The sodium-chloride cotransporter (NCC) is critical for kidney physiology1. The NCC has a major role in salt reabsorption in the distal convoluted tubule of the nephron2,3, and mutations in the NCC cause the salt-wasting disease Gitelman syndrome4. As a key player in salt handling, the NCC regulates blood pressure and is the target of thiazide diuretics, which have been widely prescribed as first-line medications to treat hypertension for more than 60 years5-7. Here we determined the structures of human NCC alone and in complex with a commonly used thiazide diuretic using cryo-electron microscopy. These structures, together with functional studies, reveal major conformational states of the NCC and an intriguing regulatory mechanism. They also illuminate how thiazide diuretics specifically interact with the NCC and inhibit its transport function. Our results provide critical insights for understanding the Na-Cl cotransport mechanism of the NCC, and they establish a framework for future drug design and for interpreting disease-related mutations.

Structure and mechanism of blood-brain-barrier lipid transporter MFSD2A.

MFSD2A is a sodium-dependent lysophosphatidylcholine symporter that is responsible for the uptake of docosahexaenoic acid into the brain1,2, which is crucial for the development and performance of the brain3. Mutations that affect MFSD2A cause microcephaly syndromes4,5. The ability of MFSD2A to transport lipid is also a key mechanism that underlies its function as an inhibitor of transcytosis to regulate the blood-brain barrier6,7. Thus, MFSD2A represents an attractive target for modulating the permeability of the blood-brain barrier for drug delivery. Here we report the cryo-electron microscopy structure of mouse MFSD2A. Our structure defines the architecture of this important transporter, reveals its unique extracellular domain and uncovers its substrate-binding cavity. The structure-together with our functional studies and molecular dynamics simulations-identifies a conserved sodium-binding site, reveals a potential lipid entry pathway and helps to rationalize MFSD2A mutations that underlie microcephaly syndromes. These results shed light on the critical lipid transport function of MFSD2A and provide a framework to aid in the design of specific modulators for therapeutic purposes.

Structure and mechanism of the mitochondrial Ca2+ uniporter holocomplex.

Mitochondria take up Ca2+ through the mitochondrial calcium uniporter complex to regulate energy production, cytosolic Ca2+ signalling and cell death1,2. In mammals, the uniporter complex (uniplex) contains four core components: the pore-forming MCU protein, the gatekeepers MICU1 and MICU2, and an auxiliary subunit, EMRE, essential for Ca2+ transport3-8. To prevent detrimental Ca2+ overload, the activity of MCU must be tightly regulated by MICUs, which sense changes in cytosolic Ca2+ concentrations to switch MCU on and off9,10. Here we report cryo-electron microscopic structures of the human mitochondrial calcium uniporter holocomplex in inhibited and Ca2+-activated states. These structures define the architecture of this multicomponent Ca2+-uptake machinery and reveal the gating mechanism by which MICUs control uniporter activity. Our work provides a framework for understanding regulated Ca2+ uptake in mitochondria, and could suggest ways of modulating uniporter activity to treat diseases related to mitochondrial Ca2+ overload.

Structure and mechanism of the cation-chloride cotransporter NKCC1.

Cation-chloride cotransporters (CCCs) mediate the electroneutral transport of chloride, potassium and/or sodium across the membrane. They have critical roles in regulating cell volume, controlling ion absorption and secretion across epithelia, and maintaining intracellular chloride homeostasis. These transporters are primary targets for some of the most commonly prescribed drugs. Here we determined the cryo-electron microscopy structure of the Na-K-Cl cotransporter NKCC1, an extensively studied member of the CCC family, from Danio rerio. The structure defines the architecture of this protein family and reveals how cytosolic and transmembrane domains are strategically positioned for communication. Structural analyses, functional characterizations and computational studies reveal the ion-translocation pathway, ion-binding sites and key residues for transport activity. These results provide insights into ion selectivity, coupling and translocation, and establish a framework for understanding the physiological functions of CCCs and interpreting disease-related mutations.

Structures and implications of the C962R protein of African swine fever virus.

African swine fever virus (ASFV) is highly contagious and can cause lethal disease in pigs. Although it has been extensively studied in the past, no vaccine or other useful treatment against ASFV is available. The genome of ASFV encodes more than 170 proteins, but the structures and functions for the majority of the proteins remain elusive, which hindered our understanding on the life cycle of ASFV and the development of ASFV-specific inhibitors. Here, we report the structural and biochemical studies of the highly conserved C962R protein of ASFV, showing that C962R is a multidomain protein. The N-terminal AEP domain is responsible for the DNA polymerization activity, whereas the DNA unwinding activity is catalyzed by the central SF3 helicase domain. The middle PriCT2 and D5_N domains and the C-terminal Tail domain all contribute to the DNA unwinding activity of C962R. C962R preferentially works on forked DNA, and likely functions in Base-excision repair (BER) or other repair pathway in ASFV. Although it is not essential for the replication of ASFV, C962R can serve as a model and provide mechanistic insight into the replicative primase proteins from many other species, such as nitratiruptor phage NrS-1, vaccinia virus (VACV) and other viruses.

Small Oversized Stent Graft Is Associated With Increased Patency for the Treatment of Central Venous Disease in Hemodialysis Patients.

PURPOSE: The purpose of this study was to identify the independent predictors of higher patency rates and investigate the selection of specifications of stent graft in the treatment of central venous disease. MATERIALS AND METHODS: This retrospective study included 54 patients who underwent stent-grafts' placement for the treatment of central venous disease between March 2017 and September 2022 at a tertiary hospital. The demographic data for the patients and the clinical data of the treated lesions were collected and analyzed. The patency rates of the treated lesions with different oversizing range were calculated via the Kaplan-Meier and log-rank analyses. The multivariate Cox proportional hazard models were constructed to identify the independent predictor of the target site primary patency. RESULTS: The median follow-up period was 21.5 months. The primary patency rates of the target sites were 90.7%, 72.2%, and 55.1% at 6, 12, and 24 months, respectively. The assisted primary patency rates of the lesions were 96.3%, 92.5%, and 80.3% at 6, 12, and 24 months, respectively. The log-rank analysis showed that the stent-grafts' placement with small oversizing had significantly higher primary patency rates than those with large oversizing (p=0.022). The multivariate analysis revealed that concomitant stenosis and large oversizing stent graft were the independent predictors of target site primary patency. CONCLUSIONS: Stent grafts showed reasonable primary patency for the treatment of central venous disease in hemodialysis patients. A stent graft with small oversizing is associated with better target site primary patency rates than those with large oversizing. CLINICAL IMPACT: Stent grafts showed reasonable primary patency for the treatment of central venous disease in hemodialysis patients. Few studies, however, have explored the efficiency of stent grafts to treat CVD by considering different factors such as sizing considerations, the rate of oversizing percentage, etc. A stent graft with small oversizing is associated with better target site primary patency rates than those with large oversizing. Excessive oversizing should be avoided to prevent infolding or stent collapse.

Association of dietary inflammatory index with risk of gestational diabetes mellitus and preeclampsia: a systematic review and meta-analysis.

Findings from observational studies have suggested a possible association between dietary inflammatory index (DII) and risk of gestational diabetes mellitus (GDM) and preeclampsia (PE). However, the results of these studies were inconclusive. A systematic review and meta-analysis was carried out to illuminate this association. Systematic literature search was conducted in PubMed, Web of Science, Cochrane Library, EMBASE, Scopus and other databases from inception until January 2023. The qualities of included studies were assessed using the Newcastle-Ottawa scale. Nine studies (seven cohort, two case-control) were included in the meta-analysis, including 11 423 participants from five different countries. The meta-analysis indicated that a 1-unit increase in the DII score, representing pro-inflammatory diet, was associated with 13 % higher risk of GDM (OR = 1·13; 95 % CI 1·02, 1·25, I2 = 68·4 %, P = 0·004) and 24 % higher risk of PE (OR = 1·24; 95 % CI 1·14, 1·35, I2 = 52·0 %, P = 0·125). Subgroup analysis found that this association was evident among studies with Chinese populations (OR = 1·16; 95 % CI 1·06, 1·28) and studies with mid pregnancy (OR = 1·20; 95 % CI 1·07, 1·34). The findings indicate that pro-inflammatory diet can increase the risk of GDM and PE. Considering some limitations in this study, more studies are needed to verify this association.

Unraveling the interplay between dyskinesia and overactive bladder symptoms in Parkinson's disease: a comprehensive cohort study based on the long-term follow-up database of Parkinson's disease.

OBJECTIVES: Overactive bladder (OAB) and dyskinesia are frequent complications in patients with Parkinson's disease (PD). However, the correlation between OAB and dyskinesia has been insufficiently explored. The purpose of this study was to examine the relationship between dyskinesia, OAB, and clinical characteristics among individuals with PD. METHODS: 1338 PD patients were included in the present study. Demographic features were compared between patients with or without dyskinesia and OAB symptoms. Logistic regression was conducted on dyskinesia to screen clinically relevant factors. Overactive Bladder Symptom Score (OABSS) was further used to stratify the association between the severity of OAB and the occurrence of dyskinesia. RESULTS: This study indicates that both dyskinesia and OAB are significantly related to disease severity and cognitive status. PD patients with dyskinesia and OAB having higher UPDRS scores (p < 0.001), H-Y scores (p < 0.001), NMSQ (p < 0.001) and MoCA scores (p < 0.001), and lower MMSE scores (p < 0.001) are identified. The multivariate logistic regression confirms that disease duration (p = 0.041), LEDD (p < 0.001), UPDRSII (p < 0.001), MoCA (p = 0.024), urgency (p < 0.001), frequency (p < 0.001), and nocturia (p = 0.002) are independent risk factors for dyskinesia. Trend analysis indicates that the risk of dyskinesia significantly increases when patients exhibit moderate to severe OAB symptoms (OABSS > 5) (p < 0.001). No significant interactions were found between OABSS and age, gender, disease duration, LEDD, and NMSQ scores in different subgroups, indicating that dyskinesia is more pronounced in patients with OABSS > 5. DISCUSSION: This study provides compelling evidence supporting the strong correlation between OAB and dyskinesia in PD patients, emphasizing the presence of shared pathogenic mechanisms between these two conditions. Our findings underscore the importance of considering both OAB and dyskinesia in the clinical management of PD, investigating the intricate connections between OAB and dyskinesia could unveil valuable insights into the complex pathophysiology of PD and potentially identify novel therapeutic targets for more effective PD treatment strategies.

X-ray and cryo-EM structures of the mitochondrial calcium uniporter.

Mitochondrial calcium uptake is critical for regulating ATP production, intracellular calcium signalling, and cell death. This uptake is mediated by a highly selective calcium channel called the mitochondrial calcium uniporter (MCU). Here, we determined the structures of the pore-forming MCU proteins from two fungi by X-ray crystallography and single-particle cryo-electron microscopy. The stoichiometry, overall architecture, and individual subunit structure differed markedly from those described in the recent nuclear magnetic resonance structure of Caenorhabditis elegans MCU. We observed a dimer-of-dimer architecture across species and chemical environments, which was corroborated by biochemical experiments. Structural analyses and functional characterization uncovered the roles of key residues in the pore. These results reveal a new ion channel architecture, provide insights into calcium coordination, selectivity and conduction, and establish a structural framework for understanding the mechanism of mitochondrial calcium uniporter function.

Survival benefits of postoperative radiotherapy in patients with cT1 - 2N1M0 breast cancer after neoadjuvant chemotherapy: a SEER-based population study.

BACKGROUND: Whether patients with cT1 - 2N1M0 breast cancer can benefit from postoperative radiotherapy (RT) after receiving neoadjuvant chemotherapy (NAC) has been controversial. Therefore, the purpose of this study was to explore whether postoperative RT can benefit this group of patients in terms of survival. METHODS: We used Surveillance, Epidemiology, and End Results (SEER) data to conduct a retrospective review of women with cT1 - 2N1M0 breast cancer diagnosed between 20 and 80 years of age who received NAC between 2010 and 2015. Our study compared the impact of postoperative RT on overall survival (OS) and cancer-specific survival (CSS) in breast cancer patients using propensity score matching (PSM) and performed subgroup analysis. RESULTS: This study finally included 1092 cT1 - 2N1M0 breast cancer patients. Regardless of the patient's PSM status, postoperative RT was significantly associated with OS of cT1-2N1M0 breast cancer patients who received NAC. Specifically, the 10-year OS rate was 78.7% before PSM matching, compared with 71.1% in patients who did not receive postoperative RT, and the difference was more significant after PSM matching, which was 83.1% and 71.1% respectively. However, postoperative RT did not significantly benefit CSS in patients with cT1 - 2N1M0 breast cancer who received NAC. The 10-year CSS rate was 81.4% VS 76.2% (P = 0.085) before PSM matching and 85.8% VS 76.2%(P = 0.076) after matching. Due to the intersection of OS and CSS curves, this restricted mean survival time (RMST) method was chosen as a supplement. After 60 months, the OS difference in RMST between the postoperative RT group and the non-radiotherapy (noRT) group was 7.37 months (95%CI: 0.54-14.21; P = 0.034), and the CSS difference was 5.18 months (95%CI: -1.31-11.68; P = 0.118). Subgroup analysis found that in patients with right-sided breast cancer, postoperative RT improved the patient's OS (HR = 0.45, 95%CI: 0.21-0.95, P = 0.037) and CSS (HR = 0.42, 95%CI: 0.18-0.98, P = 0.045). CONCLUSIONS: Our results showed that additional postoperative RT improved the OS of cT1 - 2N1M0 breast cancer patients who received NAC, but failed to improve their CSS. It is worth noting that in the subgroup analysis of patients with right-sided breast cancer, we observed significant improvements in OS and CSS. And further prospective studies are still needed to verify the effect of postoperative RT in different subgroups.

Mutant-TMEM230-induced neurodegeneration and impaired axonal mitochondrial transport.

Parkinson's disease (PD) is a neurodegenerative disease with movement disorders including resting tremor, rigidity, bradykinesia and postural instability. Recent studies have identified a new PD associated gene, TMEM230 (transmembrane protein 230). However, the pathological roles of TMEM230 and its variants are not fully understood. TMEM230 gene encodes two protein isoforms. Isoform2 is the major protein form (~95%) in human. In this study, we overexpress isoform2 TMEM230 variants (WT or PD-linked *184Wext*5 mutant) or knockdown endogenous protein in cultured SH-5Y5Y cells and mouse primary hippocampus neurons to study their pathological roles. We found that overexpression of WT and mutant TMEM230 or knockdown of endogenous TMEM230-induced neurodegeneration and impaired mitochondria transport at the retrograde direction in axons. Mutant TMEM230 caused more severe neurotoxicity and mitochondrial transport impairment than WT-TMEM230 did. Our results demonstrate that maintaining TMEM230 protein levels is critical for neuron survival and axon transport. These findings suggest that mutant-TMEM230-induced mitochondrial transport impairment could be the early event leading to neurite injury and neurodegeneration in PD development.

Transcriptomic analysis reveals the regulatory mechanism underlying the indirubin-mediated amelioration of dextran sulfate sodium-induced colitis in mice.

CONTEXT: Aryl hydrocarbon receptor (AhR) agonists are potential therapeutic agents for ulcerative colitis (UC). Indirubin (IDR), which is a natural AhR ligand approved for leukemia treatment, ameliorates dextran sulfate sodium (DSS)-induced colitis in mice. However, the therapeutic mechanisms of IDR are unknown, limiting its application. OBJECTIVE: This study explores the therapeutic mechanisms of IDR in DSS-induced colitis using transcriptomic analysis. MATERIALS AND METHODS: Male BALB/c mice were categorized to six groups: normal, DSS model (2% DSS), IDR treatment (10, 20 and 40 mg/kg), and sulfasalazine (520 mg/kg) groups. The drugs were intragastrically administered for 7 consecutive days. The disease activity index (DAI) was recorded. After euthanasia, the colon length was measured, and histopathological examination, immunohistochemistry staining using F4/80, and colonic transcriptomic analysis were conducted. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blotting (WB) were conducted to verify our findings. RESULTS: Compared with DSS, IDR treatment decreased the DAI score by 64.9% and increased colon length by 26.2%. Moreover, it alleviated mucosal injury and reduced macrophage infiltration. Transcriptomic analysis identified several downregulated genes (Igkvs and Nlrp3), as well as Nlrp3/Il1ß and hemoglobin gene networks, after IDR treatment. The abundances of NF-κB p65, NLRP3, IL-1ß, and HBA decreased by 69.1, 59.4, 81.1, and 83.0% respectively, after IDR treatment. DISCUSSION AND CONCLUSION: Apart from the well-documented NF-κB signalling pathway, IL-17A, and NLRP3-IL-1ß, the suppression of haemoglobin-induced lipid peroxidation could be a previously unknown mechanism of IDR. Our study can help improve its application for UC treatment.

Safety Review of Radiotherapy for Tumor Patients with Implantable Cardiac Pacemaker.

Permanent pacemaker implantation is one of the most effective treatments for chronic arrhythmia. However, there is a certain risk associated with radiation therapy in cancer patients with implantable cardiac pacemakers. To prevent radiotherapy-induced pacemaker failure, there are established medical guidelines for the use of pacemakers in patients undergoing radiotherapy. With advancements in science and technology, the variety of available pacemakers has considerably increased, and radiotherapy equipment has also been updated. Given the variations in irradiation methods and the types of radiation used in clinical practice, there is a pressing need for international consensus on the regulations governing the use of cardiac pacemakers in cancer patients. Currently, many countries lack clinical guidelines for radiotherapy in cancer patients with cardiac pacemakers. This review summarizes recent reports and studies from PubMed (National Center for Biotechnology Information) regarding the safety of radiotherapy in cancer patients with implanted cardiac pacemakers, and provides valuable insights for clinical practice.

Case report: Meningoencephalocele and recurrent bacterial meningitis in chronic idiopathic intracranial hypertension.

BACKGROUND: Meningoencephalocele is a rare malformation caused by congenital and acquired lesions. The association between recurrent bacterial meningitis and meningoencephaloceles with cerebrospinal fluid (CSF) leak is reported in the literature. We report a rare case of meningoencephalocele secondary to chronic idiopathic intracranial hypertension as a result of hospitalization repeatedly for meningitis due to the lack of CSF leak. CASE PRESENTATION: This study presents a case of a patient with a decade of recurrent meningitis. With clinical symptoms and imaging examination with chronic idiopathic intracranial hypertension, this patient was diagnosed with meningoencephalocele. With the treatment of acetazolamide to decrease CSF product, the patient had no recurrence of meningitis over the 6-months follow-up period. CONCLUSION: In patients with recurrent intracranial infections but no history of immunodeficiency, cranial trauma, or neurosurgery, the possibility of meningitis should be considered appropriately, even in the absence of CSF otorrhea or rhinorrhea.

A novel compound heterozygous SPG7 variant is associated with progressive spastic ataxia and persecutory delusions found in Chinese patients: two case reports.

BACKGROUND: Hereditary spastic paraplegia 7 (SPG7) is one of the subtypes of autosomal-recessive hereditary spastic paraplegia, which is a clinically heterogeneous neurodegenerative disorder. SPG7 often displays a complicated phenotype, including optic atrophy, ophthalmoparesis, and impaired emotional communication. In the Chinese population, sporadic cases of SPG7 variant-associated spastic ataxia are rarely reported. CASE PRESENTATION: We carefully analysed the clinical features, imaging and genetic tests of two sporadic patients with SPG7, both from the Hebei region of China. One patient presented with progressive bilateral lower limb weakness, spastic-ataxia and no cognitive impairment. Brain MRI revealed mild cerebellar atrophy. Genetic analysis revealed c.1150_1151insCTAC (p.G384Afs*13) frameshift variant and exon1-3 heterozygous deletion. The other patient presented with progressive bilateral lower limb weakness, ataxia, dysarthria and a mild psychosis associated with persecutory delusions, which drew almost no attention, in addition to mild cognitive impairments characterized by a decrease in verbal memory and executive function. Genetic analysis identified two heterozygous variants in the SPG7 gene: c.1150_1151insCTAC (p.G384Afs*13) and c.1496delC (p.Q500Sfs*13). CONCLUSIONS: The c.1496delC (p.Q500Sfs*13) variant in exon 11 has not been reported before. The c.1150_1151insCTAC variant is speculated to be a hotspot variant in the Chinese population. Patients with SPG7 may have cognitive impairments and psychosis, displaying specific characteristics, which should be of concern.

Fiber selectivity of peripheral neuropathy in patients with Parkinson's disease.

OBJECTIVE: To determine the function of each type of peripheral nerve fiber and investigate the possible role of levodopa (LD) in peripheral neuropathy (PN) in Parkinson's disease (PD) patients. METHODS: We enrolled 60 patients with idiopathic PD. All PD patients were divided into three groups: levodopa exposure >3 years (LELD), levodopa exposure ≤3 years (SELD) and de novo patients with PD (NOLD). The current perception threshold (CPT), which was measured by Neurometer at 2000, 250 and 5 Hz, the level of homocysteine, Vitamin B12 and folic acid in plasma, were compared with those of sex- and age-matched healthy controls (HCs). RESULTS: Current perception threshold was higher at 250 Hz (p < .05) and 5 Hz (p < .05) in the LELD group than the NOLD, SELD, and control group. CPT was lower at 5 Hz in the NOLD than in the HCs group (p < .05). The CPT of the more affected side of PD patients was positively correlated with H-Y stage at 5 Hz current stimulation (r = .42, p = .01). Multivariate logistic regression analysis showed that elevated homocysteine levels were the risk factor of sensory nerve injury in PD patients (p < .01). Serum homocysteine levels were positively correlated with levodopa (LD) daily dose, LD equivalent daily dose, and LD cumulative lifetime dose (p < .05). CONCLUSIONS: Peripheral neuropathy in PD patients can occur in the early stage of PD exhibiting as hyperesthesia and is fiber selectivity, especially for Aδ and C nerve fibers. PN in PD patients is related to PD itself and long-term LD exposure. Elevated plasma homocysteine is a risk factor for PN in PD patients.

Relationship between 25-Hydroxyvitamin D, bone density, and Parkinson's disease symptoms.

OBJECTIVES: Vitamin D deficiency is widespread in patients with Parkinson's disease (PD). Our aim was to determine whether serum vitamin D levels correlated with bone mineral density (BMD) and non-motor symptoms in patients with PD. MATERIALS & METHODS: A consecutive series of 182 patients with PD and 185 healthy controls were included. Serum 25-hydroxyvitamin D (25[OH]D) levels were measured by immunoassay, while BMD of the lumbar spine and femoral neck was measured by dual-energy X-ray absorptiometry. Associations between serum vitamin D levels and clinical data were evaluated using partial correlation analysis. RESULTS: Patients with PD had significantly lower serum 25(OH)D levels relative to healthy controls (49.75 ± 14.11 vs 43.40 ± 16.51, P < 0.001). Furthermore, PD patients with lower vitamin D levels had a significantly higher frequency of falls (P = 0.033) and insomnia (P = 0.015). They also had significantly higher scores for the Pittsburgh Sleep Quality Index (PSQI; P = 0.014), depression (P = 0.020), and anxiety (P = 0.009). Finally, patients with PD also had a significantly lower mean BMD of the lumbar spine (P = 0.011) and femoral neck (P < 0.001). After adjusting for age, sex, and body mass index, vitamin D levels significantly correlated with falls, insomnia, and scores for the PSQI, depression, and anxiety. CONCLUSIONS: In patients with PD, vitamin D levels significantly correlated with falls and some non-motor symptoms. However, no associations were found between BMD and the serum 25(OH)D levels in patients with PD. Thus, vitamin D supplementation is a potential therapeutic for non-motor PD symptoms.

Structure-based design of agarase AgWH50C from Agarivorans gilvus WH0801 to enhance thermostability.

AgWH50C, an exo-ß-agarase of GH50 isolated from Agarivorans gilvus WH0801, plays a key role in the enzymatic production of neoagarobiose, which has great application prospect in the cosmetics and pharmaceutical industry. In contrast, the poor thermostability becomes the main obstructive factor of glycoside hydrolase (GH) family 50 agarases, including AgWH50C. Herein, based on the AgWH50C crystal structure, we designed several mutants by a multiple cross-linked rational design protocol used thermostability predicting softwares ETSS, PoPMuSiC, and HotMuSiC. To our surprise, the mutant K621F increased its relative activity by as much as 45% and the optimal temperature increased to 38 °C compared to that of wild-type, AgWH50C (30 °C). The thermostability of K621F also exhibited a substantial improvement. Considering that the gelling temperature of the agarose is higher than 35 °C, K621F can be used to hydrolyze agarose for neoagarobiose production.

Isolation of Bactrian Camel Single Domain Antibody for Parathion and Development of One-Step dc-FEIA Method Using VHH-Alkaline Phosphatase Fusion Protein.

A heavy chain variable fragment of heavy chain only antibodies derived from camelids termed VHH shows beneficial characteristics for immunoassay in terms of high sensitivity, outstanding stability and ease in expression. In the present study, we isolated six VHHs from phage display library against parathion, which is a widely used organophosphorus pesticide with high toxicity and persistence. One of six selected VHHs named VHH9, showed highest specificity and superior thermo-stability. A VHH9-alkaline phosphatase (AP) fusion was constructed and used to establish a one-step direct competitive fluorescence enzyme immunoassay (dc-FEIA) with a half maximal inhibitory concentration (IC50) of 1.6 ng/mL and a limit of detection of 0.2 ng/mL which was 4-fold or 3-fold higher sensitivity than direct competitive enzyme-linked immunoassay (dc-ELISA) and indirect competitive enzyme-linked immunoassay (ic-ELISA) for parathion. Furthermore, our assay indicated a 50% reduction on operation time compared with the ic-ELISA method. The presented immunoassay was validated with spiked Chinese cabbage, cucumber, and lettuce samples, and confirmed by UPLC-MS/MS. The results indicated that the VHH-AP-based dc-FEIA is a reproducible detection assay for parathion residues in vegetable samples.

Structural basis of nonribosomal peptide macrocyclization in fungi.

Nonribosomal peptide synthetases (NRPSs) in fungi biosynthesize important pharmaceutical compounds, including penicillin, cyclosporine and echinocandin. To understand the fungal strategy of forging the macrocyclic peptide linkage, we determined the crystal structures of the terminal condensation-like (CT) domain and the holo thiolation (T)-CT complex of Penicillium aethiopicum TqaA. The first, to our knowledge, structural depiction of the terminal module in a fungal NRPS provides a molecular blueprint for generating new macrocyclic peptide natural products.