A fragment-based approach to assess the ligandability of ArgB, ArgC, ArgD and ArgF in the L-arginine biosynthetic pathway of Mycobacterium tuberculosis.

The L-arginine biosynthesis pathway consists of eight enzymes that catalyse the conversion of L-glutamate to L-arginine. Arginine auxotrophs (argB/argF deletion mutants) of Mycobacterium tuberculosis are rapidly sterilised in mice, while inhibition of ArgJ with Pranlukast was found to clear chronic M. tuberculosis infection in a mouse model. Enzymes in the arginine biosynthetic pathway have therefore emerged as promising targets for anti-tuberculosis drug discovery. In this work, the ligandability of four enzymes of the pathway ArgB, ArgC, ArgD and ArgF is assessed using a fragment-based approach. We identify several hits against these enzymes validated with biochemical and biophysical assays, as well as X-ray crystallographic data, which in the case of ArgB were further confirmed to have on-target activity against M. tuberculosis. These results demonstrate the potential for more enzymes in this pathway to be targeted with dedicated drug discovery programmes.

Inhibiting Mycobacterium tuberculosis CoaBC by targeting an allosteric site.

Coenzyme A (CoA) is a fundamental co-factor for all life, involved in numerous metabolic pathways and cellular processes, and its biosynthetic pathway has raised substantial interest as a drug target against multiple pathogens including Mycobacterium tuberculosis. The biosynthesis of CoA is performed in five steps, with the second and third steps being catalysed in the vast majority of prokaryotes, including M. tuberculosis, by a single bifunctional protein, CoaBC. Depletion of CoaBC was found to be bactericidal in M. tuberculosis. Here we report the first structure of a full-length CoaBC, from the model organism Mycobacterium smegmatis, describe how it is organised as a dodecamer and regulated by CoA thioesters. A high-throughput biochemical screen focusing on CoaB identified two inhibitors with different chemical scaffolds. Hit expansion led to the discovery of potent and selective inhibitors of M. tuberculosis CoaB, which we show to bind to a cryptic allosteric site within CoaB.

Surgical Management of Esophageal Achalasia in Pediatrics: A Systematic Review.

INTRODUCTION: There are no evidence-based guidelines on the surgical management of esophageal achalasia (OA) in children. This can be a challenging condition with significant physical and psychological morbidity. Our aim was to identify the most common management modalities and their outcomes. MATERIALS AND METHODS: A systematic review was performed through a literature search of health care databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, aiming at identifying pediatric series discussing the diagnosis and management of OA. Duplicates, case series with < 9 patients, and follow-up of < 1 year were excluded. The included papers were analyzed for diagnostic methods, primary treatment method, complications, follow-up duration, outcome measures recorded, and outcome. RESULTS: Data from 33 papers for 742 children treated for OA was analyzed. Eleven mentioned multiple management modalities. In summary, 25 described Heller's esophagomyotomy (HM), 13 esophageal dilatation (EOD), and 6 peroral esophageal myotomy (POEM). Mean follow-up was 43.7 months (12-180). Outcome measures were heterogeneous. However, analysis of reported success showed a mean success of 78% for HM (p = 1.79 × 10-7), 44.9% for EOD (p = 0.24), and 99.3% for POEM (p = 0.001). Reported complications were 12.8% for HM, 5% for EOD, and 24.4% for POEM. Further interventions were required for 10.9% of HM, 62.3% of EOD, and 0.01% of POEM patient groups. CONCLUSION: Methods of diagnosis and measures of successful outcomes were heterogeneous, limiting the strength of evidence. HM showed superior short-term success rates to EOD. POEM is a promising modality but requires investment in equipment and training. Information about sustainability of response and long-term outcomes is lacking.

Aromatic Residues in the Fourth Transmembrane-Spanning Helix M4 Are Important for GABAρ Receptor Function.

GABAρ receptors are a subfamily of the GABAA receptor family of pentameric ligand-gated ion channels (pLGICs). Each of the five subunits has four transmembrane α-helices (M1-M4), with M4 most distant from the central pore. Aromatic residues in this M4 helix are important for receptor assembly in pLGICs and also may interact with adjacent lipids and/or residues in neighboring α-helices and the extracellular domain to modify or enable channel gating. This study examines the role of M4 receptor aromatic residues in the GABAρ receptor transmembrane domain using site-directed mutagenesis and subsequent expression in HEK293 cells, probing functional parameters using a fluorescent membrane-potential-sensitive dye. The data indicate that many of the aromatic residues in M4 play a role in receptor function, as substitution with other residues can ablate and/or modify functional parameters. Modeling showed that these residues likely interact with residues in the adjacent M1 and M3 α-helices and/or residues in the Cys-loop in the extracellular domain. We suggest that many of these aromatic interactions contribute to an "aromatic zipper", which allows interactions between M4 and the rest of the receptor that are essential for function. Thus, the data support other studies showing that M4 does not play a passive role in "protecting" the other transmembrane helices from the lipid bilayer but is actively involved in the function of the protein.