The structural basis of lipid scrambling and inactivation in the endoplasmic reticulum scramblase TMEM16K

Membranes in cells have defined distributions of lipids in each leaflet, controlled by lipid scramblases and flip/floppases. However, for some intracellular membranes such as the endoplasmic reticulum (ER) the scramblases have not been identified. Members of the TMEM16 family have either lipid scramblase or chloride channel activity. Although TMEM16K is widely distributed and associated with the neurological disorder autosomal recessive spinocerebellar ataxia type 10 (SCAR10), its location in cells, function and structure are largely uncharacterised. Here we show that TMEM16K is an ER-resident lipid scramblase with a requirement for short chain lipids and calcium for robust activity. Crystal structures of TMEM16K show a scramblase fold, with an open lipid transporting groove. Additional cryo-EM structures reveal extensive conformational changes from the cytoplasmic to the ER side of the membrane, giving a state with a closed lipid permeation pathway. Molecular dynamics simulations showed that the open-groove conformation is necessary for scramblase activity

Structures of DPAGT1 explain glycosylation disease mechanisms and advance TB antibiotic design

Summary: Protein N-glycosylation is a widespread post-translational modification. The first committed step in this process is catalysed by dolichyl-phosphate N-acetylglucosamine-phosphotransferase DPAGT1 (GPT/E.C. 2.7.8.15). Missense DPAGT1 variants cause congenital myasthenic syndrome and disorders of glycosylation. In addition, naturally-occurring bactericidal nucleoside analogues such as tunicamycin are toxic to eukaryotes due to DPAGT1 inhibition, preventing their clinical use. Our structures of DPAGT1 with the substrate UDP-GlcNAc and tunicamycin reveal substrate binding modes, suggest a mechanism of catalysis, provide an understanding of how mutations modulate activity (thus causing disease) and allow design of non-toxic “lipid-altered” tunicamycins. The structure-tuned activity of these analogues against several bacterial targets allowed the design of potent antibiotics for Mycobacterium tuberculosis, enabling treatment in vitro, in cellulo and in vivo, providing a promising new class of antimicrobial drug

High-Throughput Mass Spectrometry Applied to Structural Genomics

Mass spectrometry (MS) remains under-utilized for the analysis of expressed proteins because it is inaccessible to the non-specialist, and sample-turnaround from service labs is slow. Here, we describe 3.5 min Liquid-Chromatography (LC)-MS and 16 min LC-MSMS methods which are tailored to validation and characterization of recombinant proteins in a high throughput structural biology pipeline. We illustrate the type and scope of MS data typically obtained from a 96-well expression and purification test for both soluble and integral membrane proteins (IMPs), and describe their utility in the selection of constructs for scale-up structural work, leading to cost and efficiency savings. We propose that value of MS data lies in how quickly it becomes available and that this can fundamentally change the way in which it is used

Using the Journey to Health and Immunization (JTHI) Framework to Engage Stakeholders in Identifying Behavioral and Social Drivers of Routine Immunization in Nepal

Although the Government of Nepal has achieved high and sustained childhood vaccination coverage, reaching under-immunized and zero-dose children requires different approaches. Behavioral science offers promise in better understanding the drivers of vaccination and development of more effective programs; however, the application of behavioral science to immunization programs in Nepal is nascent. Through the Behavioral Science Immunization Network, JSI, UNICEF Nepal, and Dhulikhel Hospital–Kathmandu University School of Medical Sciences established a Behavioral Science Center to engage a diverse group of stakeholders in increasing the capacity of practitioners to use behavioral science in immunization programming. As a result of the engagement during formative research, government stakeholders requested and applied tools from behavioral science to solve different immunization challenges. Of particular value was the use of the Journey to Health and Immunization framework, which helped stakeholders identify behavioral and social drivers of zero-dose communities in Kathmandu. Our experience in Nepal demonstrates that there is strong demand for approaches and tools from behavioral science to use in relation to immunization and that this type of engagement model is effective for generating demand for and strengthening capacity to use behavioral science approaches

Study on the Synthesis of ZnO Nanoparticles Using <i>Azadirachta indica</i> Extracts for the Fabrication of a Gas Sensor

This paper compared the effects of A. indica plant proteins over chemical methods in the morphology of zinc oxide nanoparticles (ZnO NPs) prepared by a co-precipitation method, and ethanol sensing performance of prepared thin films deposited over a fluorene-doped tin oxide (FTO) bind glass substrate using spray pyrolysis technique. The average crystallite sizes and diameters of the grain-sized cluster ZnO NPs were 25 and (701.79 ± 176.21) nm for an undoped sample and 20 and (489.99 ± 112.96) nm for A. india dye-doped sample. The fourier transform infrared spectroscopy (FTIR) analysis confirmed the formation of the Zn–O bond at 450 cm−1, and also showed the presence of plant proteins due to A. indica dye extracts. ZnO NPs films exhibited good response (up to 51 and 72% for without and with A. indica dye-doped extracts, respectively) toward ethanol vapors with quick response-recovery characteristics at a temperature of 250 °C for undoped and 225 °C for A. indica dye-doped ZnO thin films. The interaction of A. indica dye extracts helps to decrease the operating temperature and increased the response and recovery rates of the sensor, which may be due to an increase in the specific surface area, resulting in adsorption of more oxygen and hence high response results

Human Dolichyl-Phosphate Alpha-N-Acetyl glucosaminyl transferase (DPAGT1); A Target Enabling Package

<p>The ER integral membrane enzyme dolichyl-phosphate alpha-N-acetyl glucosaminyl phosphotransferase (DPAGT1) catalyses the first step in the synthesis of the oligosaccharide-P-P-dolichol unit which provides the glycans structure for N-glycosylation of proteins. Mutations in DPAGT1 cause two muscle weakness conditions, limb-girdle congenital myasthenic syndrome (CMS) and congenital disorder of glycosylation type 1j (CDG1j). DPAGT1 overexpression has also been implicated in oral cancer. We have produced and solved structures of this integral membrane enzyme, DPAGT1 with the V264G mutation found in a patient with CMS, and complexes with a 50 nM inhibitor, tunicamycin. We have developed enzymatic activity and thermostability assays which have allowed us to assess the activity and stability of DPAGT1 mutants and the effect of small molecules. There are > 20 DPAGT1 associated missense variants in patients with CMS and CDG1j. We have mapped these mutations to the structure, and we will used the assays described here to assess how the activity and stability of DPAGT1 is affected by these missense variants.</p

Human Dolichyl-Phosphate Alpha-N-Acetyl glucosaminyl transferase (DPAGT1); A Target Enabling Package

<p>The ER integral membrane enzyme dolichyl-phosphate alpha-N-acetyl glucosaminyl phosphotransferase (DPAGT1) catalyses the first step in the synthesis of the oligosaccharide-P-P-dolichol unit which provides the glycans structure for N-glycosylation of proteins. Mutations in DPAGT1 cause two muscle weakness conditions, limb-girdle congenital myasthenic syndrome (CMS) and congenital disorder of glycosylation type 1j (CDG1j). DPAGT1 overexpression has also been implicated in oral cancer. We have produced and solved structures of this integral membrane enzyme, DPAGT1 with the V264G mutation found in a patient with CMS, and complexes with a 50 nM inhibitor, tunicamycin. We have developed enzymatic activity and thermostability assays which have allowed us to assess the activity and stability of DPAGT1 mutants and the effect of small molecules. There are > 20 DPAGT1 associated missense variants in patients with CMS and CDG1j. We have mapped these mutations to the structure, and we will used the assays described here to assess how the activity and stability of DPAGT1 is affected by these missense variants.</p

Human Dolichyl-Phosphate Alpha-N-Acetyl glucosaminyl transferase (DPAGT1); A Target Enabling Package

<p>The ER integral membrane enzyme dolichyl-phosphate alpha-N-acetyl glucosaminyl phosphotransferase (DPAGT1) catalyses the first step in the synthesis of the oligosaccharide-P-P-dolichol unit which provides the glycans structure for N-glycosylation of proteins. Mutations in DPAGT1 cause two muscle weakness conditions, limb-girdle congenital myasthenic syndrome (CMS) and congenital disorder of glycosylation type 1j (CDG1j). DPAGT1 overexpression has also been implicated in oral cancer. We have produced and solved structures of this integral membrane enzyme, DPAGT1 with the V264G mutation found in a patient with CMS, and complexes with a 50 nM inhibitor, tunicamycin. We have developed enzymatic activity and thermostability assays which have allowed us to assess the activity and stability of DPAGT1 mutants and the effect of small molecules. There are > 20 DPAGT1 associated missense variants in patients with CMS and CDG1j. We have mapped these mutations to the structure, and we will used the assays described here to assess how the activity and stability of DPAGT1 is affected by these missense variants.</p