Structural basis for cell surface patterning through NetrinG-NGL interactions

Brain wiring depends on cells making highly localized and selective connections through surface protein-protein interactions, including those between NetrinGs and NetrinG ligands (NGLs). The NetrinGs are members of the structurally uncharacterized netrin family. We present a comprehensive crystallographic analysis comprising NetrinG1-NGL1 and NetrinG2-NGL2 complexes, unliganded NetrinG2 and NGL3. Cognate NetrinG-NGL interactions depend on three specificity-conferring NetrinG loops, clasped tightly by matching NGL surfaces. We engineered these NGL surfaces to implant custom-made affinities for NetrinG1 and NetrinG2. In a cellular patterning assay, we demonstrate that NetrinG-binding selectivity can direct the sorting of a mixed population of NGLs into discrete cell surface subdomains. These results provide a molecular model for selectivity-based patterning in a neuronal recognition system, dysregulation of which is associated with severe neuropsychological disorders

YacG from Escherichia coli is a specific endogenous inhibitor of DNA gyrase

We assign a function for a small protein, YacG encoded by Escherichia coli genome. The NMR structure of YacG shows the presence of an unusual zinc-finger motif. YacG was predicted to be a part of DNA gyrase interactome based on protein–protein interaction network. We demonstrate that YacG inhibits all the catalytic activities of DNA gyrase by preventing its DNA binding. Topoisomerase I and IV activities remain unaltered in the presence of YacG and its action appears to be restricted only to DNA gyrase. The inhibition of the enzyme activity is due to the binding of YacG to carboxyl terminal domain of GyrB. Overexpression of YacG results in growth inhibition and alteration in DNA topology due to uncontrolled inhibition of gyrase

YacG from Escherichia coli is a specific endogenous inhibitor of DNA gyrase

We assign a function for a small protein, YacG encoded by Escherichia coli genome. The NMR structure of YacG shows the presence of an unusual zinc-finger motif. YacG was predicted to be a part of DNA gyrase interactome based on protein–protein interaction network. We demonstrate that YacG inhibits all the catalytic activities of DNA gyrase by preventing its DNA binding. Topoisomerase I and IV activities remain unaltered in the presence of YacG and its action appears to be restricted only to DNA gyrase. The inhibition of the enzyme activity is due to the binding of YacG to carboxyl terminal domain of GyrB. Overexpression of YacG results in growth inhibition and alteration in DNA topology due to uncontrolled inhibition of gyrase

Heliyon

Purpose: Restraint is often used when administering procedures to children. However, no metrologically scale to measure the restraint intensity had yet been validated. This study validated the metrological criteria of a scale measuring the restraint intensity, Procedural Restraint Intensity in Children (PRIC), used during procedures in children. Design and methods: The PRIC scale performance was measured by a group of 7 health professionals working in a children's hospital, by watching 20 videos of health care procedures. This group included 2 physicians, 1 pediatric resident, and 4 nurses. The intra-class correlation coefficients were calculated to evaluate the inter-rater and test-retest reliability and the construct validity with the correlation between PRIC scale and a numerical rating scale. Results: One hundred and forty measurements were made. Inter-rater and test-retest correlation coefficients were 0.98 and 0.98, respectively. The 2 scales were positively correlated with a Spearman coefficient of 0.93. Conclusions: This study validated the Procedural Restraint Intensity in Children (PRIC) scale in metrological terms with some limitation. However, there is not gold standard scale to precisely validate the reliability of this tool and this study has been conducted in "experimental" conditions. Nevertheless, this is the first scale measuring the intensity of physical restraint with a metrological validation. The next step will be to validate it in real clinical situations

Contribution of the a-baumannii A1S_0114 gene to the interaction with eukaryotic cells and virulence

Genetic and functional studies showed that some components of the Acinetobacter baumannii ATCC 17978 A1S_0112-A1S_0119 gene cluster are critical for biofilm biogenesis and surface motility. Recently, our group has shown that the A1S_0114 gene was involved in biofilm formation, a process related with pathogenesis. Confirming our previous results, microscopy images revealed that the ATCC 17978 10114 derivative lacking this gene was unable to form a mature biofilm structure. Therefore, other bacterial phenotypes were analyzed to determine the role of this gene in the pathogenicity of A. baumannii ATCC 17978. The interaction of the ATCC 17978 parental strain and the 10114 mutant with A549 human alveolar epithelial cells was quantified revealing that the A1S_0114 gene was necessary for proper attachment to A549 cells. This dependency correlates with the negative effect of the A1S_0114 deletion on the expression of genes coding for surface proteins and pili-assembly systems, which are known to play a role in adhesion. Three different experimental animal models, including vertebrate and invertebrate hosts, confirmed the role of the A1S_0114 gene in virulence. All of the experimental infection assays indicated that the virulence of the ATCC 17978 was significantly reduced when this gene was inactivated. Finally, we discovered that the A1S_0114 gene was involved in the production of a small lipopeptide-like compound herein referred to as acinetin 505 (Ac-505). Ac-505 was isolated from ATCC 17978 spent media and its chemical structure was interpreted by mass spectrometry. Overall, our observations provide novel information on the role of the A1S_0114 gene in A. baumannii’s pathobiology and lay the foundation for future work to determine the mechanisms by which Ac-505, or possibly an Ac-505 precursor, could execute critical functions as a secondary metaboliteS

A Minimal Threshold of c-di-GMP Is Essential for Fruiting Body Formation and Sporulation in Myxococcus xanthus

Generally, the second messenger bis-(3’-5’)-cyclic dimeric GMP (c-di-GMP) regulates the switch between motile and sessile lifestyles in bacteria. Here, we show that c-di-GMP is an essential regulator of multicellular development in the social bacterium Myxococcus xanthus. In response to starvation, M. xanthus initiates a developmental program that culminates in formation of spore-filled fruiting bodies. We show that c-di-GMP accumulates at elevated levels during development and that this increase is essential for completion of development whereas excess c-di-GMP does not interfere with development. MXAN3735 (renamed DmxB) is identified as a diguanylate cyclase that only functions during development and is responsible for this increased c-di-GMP accumulation. DmxB synthesis is induced in response to starvation, thereby restricting DmxB activity to development. DmxB is essential for development and functions downstream of the Dif chemosensory system to stimulate exopolysaccharide accumulation by inducing transcription of a subset of the genes encoding proteins involved in exopolysaccharide synthesis. The developmental defects in the dmxB mutant are non-cell autonomous and rescued by co-development with a strain proficient in exopolysaccharide synthesis, suggesting reduced exopolysaccharide accumulation as the causative defect in this mutant. The NtrC-like transcriptional regulator EpsI/Nla24, which is required for exopolysaccharide accumulation, is identified as a c-diGMP receptor, and thus a putative target for DmxB generated c-di-GMP. Because DmxB can be—at least partially—functionally replaced by a heterologous diguanylate cyclase, these results altogether suggest a model in which a minimum threshold level of c-di-GMP is essential for the successful completion of multicellular development in M. xanthus