The transmembrane protein bacterioopsin affects the polarity of the hydrophobic core of the host lipid bilayer

AbstractInfluence of the transmembrane protein bacterioopsin (the retinal-free form of bacteriorhodopsin) on the polarity of egg-phosphatidylcholine bilayers was studied by means of a steady-state and time-resolved fluorescence approach exploiting the solvatochromic properties of the 2-anthroyl fluorophore. Introduced in phosphatidylcholine molecules in the form of 8-(2-anthroyl)octanoic acid, this fluorophore probed the hydrocarbon core of the lipid bilayer. As previously shown (E. Pérochon et al., Biochemistry 31 (1992) 7672–7682), water molecules were detected in this region of the terminal part of the lipid acyl chains. Their number was considerably reduced upon addition of bacterioopsin to the lipids. This was assessed by a blue shift in the fluorescence emission spectra of the probe and a marked decrease in the fractional population of fluorophores interacting with water, to the benefit of those experiencing a hydrophobic environment. In agreement with current theories, this decrease in the hydration of the bilayer may be linked to an increase in the acyl chain order and a decrease in the lateral diffusion coefficient of lipids near the protein. The data obtained at high protein concentration accounts for a protein/lipid interface which is much less hydrated than the hydrophobic core of a protein-free lipid bilayer

Returns to farm child labor in Tanzania

In developing countries, the opportunity costs of children’s time can significantly hinder universal education. This paper studies one of these opportunity costs: we estimate the agricultural productivity of children aged 10 to 15 years old using the LSMS-ISA panel survey in Tanzania. Since child labor can be endogenous, we exploit the panel structure of the data and instrument child labor with changes in the age composition of the household. One day of child work leads to an increase in production value by roughly US$0.89. Children enrolled in school work 26 fewer days than nonenrolled children. Compensating enrolled children for loss in income can be accomplished with monthly payments of$1.92. However, a complete simulation of a hypothetical conditional cash transfer shows that even $10/month transfers would fail to achieve universal school enrollment of children aged 10 to 15 years old

Characterization and molecular basis of the oligomeric structure of HIV-1 Nef protein

International audienceThe Nef protein of human immunodeficiency virus type I~HIV-1! is an important determinant for the onset of AIDS disease. The self-association properties of HIV-1 Nef are analyzed by chemical cross-linking, dynamic light scattering, equilibrium analytical ultracentrifugation, and NMR spectroscopy. The experimental data show that the HIV-1 Nef core domain forms stable homo-dimers and trimers in solution, but not higher oligomers. These Nef homomers are not covalently linked by disulfide bridges, and the equilibrium between these forms is dependent on the Nef concentration. We further provide the molecular basis for the Nef core dimers and trimers obtained by analysis of crystallographic models. Oligomerization of biological polypeptides is a common tool used to trigger events in cellular signaling and endocytosis, both of which are targeted by Nef. The quaternary structure of Nef may be of physiological importance and may help to connect its cellular targets or to increase affinity of the viral molecule for its ligands. The herein described models for Nef dimers and trimers will allow further mutational studies to elucidate their role in vivo. These results provide novel insight into the structural and functional relationships of this important viral protein. Moreover, the oligomer interface may represent a novel target for the design of antiviral agents

Formation of linear inverted repeat amplicons following targeting of an essential gene in Leishmania

Attempts to inactivate an essential gene in the protozoan parasite Leishmania have often led to the generation of extra copies of the wild-type alleles of the gene. In experiments with Leishmania tarentolae set up to disrupt the gene encoding the J-binding protein 1 (JBP1), a protein binding to the unusual base β-d-glucosyl-hydroxymethyluracil (J) of Leishmania, we obtained JBP1 mutants containing linear DNA elements (amplicons) of ∼100 kb. These amplicons consist of a long inverted repeat with telomeric repeats at both ends and contain either the two different targeting cassettes used to inactivate JBP1, or one cassette and one JBP1 gene. Each long repeat within the linear amplicons corresponds to sequences covering the JBP1 locus, starting at the telomeres upstream of JBP1 and ending in a ∼220 bp sequence repeated in an inverted (palindromic) orientation downstream of the JBP1 locus. We propose that these amplicons have arisen by a template switch inside a DNA replication fork involving the inverted DNA repeats and helped by the gene targeting

Expression, purification, crystallization and preliminary X-ray analysis of the cathelicidin motif of the protegrin-3 precursor

International audienc

The Host Microbiota Contributes to Early Protection Against Lung Colonization by Mycobacterium tuberculosis

Tuberculosis (TB), caused by the airborne bacterial pathogen Mycobacterium tuberculosis, remains a major source of morbidity and mortality worldwide. So far, the study of host-pathogen interactions in TB has mostly focused on the physiology and virulence of the pathogen, as well as, on the various innate and adaptive immune compartments of the host. Microbial organisms endogenous to our body, the so-called microbiota, interact not only with invading pathogens, but also with our immune system. Yet, the impact of the microbiota on host defense against M. tuberculosis remains poorly understood. In order to address this question, we adapted a robust and reproducible mouse model of microbial dysbiosis based on a combination of wide-spectrum antibiotics. We found that microbiota dysbiosis resulted in an increased early colonization of the lungs by M. tuberculosis during the first week of infection, correlating with an altered diversity of the gut microbiota during this time period. At the cellular level, no significant difference in the recruitment of conventional myeloid cells, including macrophages, dendritic cells and neutrophils, to the lungs could be detected during the first week of infection between microbiota-competent and -deficient mice. At the molecular level, microbiota depletion did not impact the global production of pro-inflammatory cytokines, such as interferon (IFN)γ, tumor necrosis factor (TNF)α and interleukin (IL)-1β in the lungs. Strikingly, a reduced number of mucosal-associated invariant T (MAIT) cells, a population of innate-like lymphocytes whose development is known to depend on the host microbiota, was observed in the lungs of the antibiotics-treated animals after 1week of infection. These cells produced less IL-17A in antibiotics-treated mice. Notably, dysbiosis correction through the inoculation of a complex microbiota in antibiotics-treated animals reversed these phenotypes and improved the ability of MAIT cells to proliferate. Altogether, our results demonstrate that the host microbiota contributes to early protection of lung colonization by M. tuberculosis, possibly through sustaining the function(s) of MAIT cells. Our study calls for a better understanding of the impact of the microbiota on host-pathogen interactions in TB. Ultimately, this study may help to develop novel therapeutic approaches based on the use of beneficial microbes, or components thereof, to boost anti-mycobacterial immunity

Aqueduc et structures hydrauliques de la <i>villa</i> de Richeaume I à Puyloubier (Bouches-du-Rhône)

International audienceEine von 1998 bis 2003 an der antiken Fundstelle von Richeaume I (Puyloubier, Dép. Bouches-du-Rhône) durchgeführte Plangrabung führte zur Entdeckung einer ausgedehnten Villenanlage. Sie nimmt eine Fläche von mehr als 5.000 m2 ein und war vom ersten Jahrhundert v. Chr. bis zu Beginn des sechsten Jahrhunderts n. Chr. belegt. Sie war durch eine Wasserleitung versorgt, die die Quellen im Norden des Geländes faβt, und von einer bestimmten Anzahl ländlicher Siedelplätze umgeben, die häufig schon in der jüngeren Eisenzeit bestanden. Die auf 2.000 m2 freigelegten archäologischen Überreste betreffen die Wohnbereiche und die landwirtschaftlichen Bereiche der frühkaiserzeitlichen und spätantiken Villa sowie verschiedene wasserbauliche Vorrichtungen (Zierbecken, Leitungskanäle, Abwasserleitungen, Staumauern, Entwässerungsgräben und Reste der Wasserleitung). Die hier vorgetragenen Überlegungen beziehen sich auf die wasserbaulichen Anlagen, die durch geophysikalische Prospektion und archäologische Grabungen auf dem Osthang des Platzes zwischen 315,94 m und 314,05 m ü. N. N. entdeckt wurden. Von diesen Anlagen (Staumauer, Altarm eines Gewässerlaufs, Abschnitte der Wasserleitung) fallen insbesondere Überreste einer Wasserleitung auf die man nur mit der Wasserversorgung der Wohn- und Stallbereiche der weiter bergauf gelegenen Villa in Verbindung bringen kann. Die beschriebene Vorrichtung, bei der die stark abschüssige Hanglage die Errichtung eines gewaltigen Unterbaus erzwang, dürfte mit der Versorgung eines der benachbarten Gebäude zusammenhängen, dessen genaue Funktion noch zu untersuchen wäre.A research excavation on the Richeaume I site (Puyloubier, Bouches-du-Rhône) took place between 1998 and 2003. This revealed the presence of a substantial villa, covering an area of 5 000 m2 that was occupied from the 1st century BC through to the 4th century AD. An aqueduct, which channelled water from a number of springs to the north of the site, supplied the site. A number of other sites that were initially settled during the late Iron Age surround Richeaume I. The archaeological remains excavated covered an area of 2 000 m2 and revealed elements of the agricultural and domestic areas of the villa, as well as hydrological structures (ornamental pond, water conduits, sewers, dykes, drains and aqueduct remains). This article presents an analysis of the hydrological structures discovered by geophysical survey, which were subsequently excavated, on the western side of the site between 315,94 m and 314,05 m above sea level. Within these structures (dyke, palaeochannel and sections of aqueduct) the most important element is an aqueduct that cannot be directly associated with the supply of water to the residential and agricultural parts of the villa upstream. The presence of this structure, which is characterised by a substantial slope, required the construction of a substantial foundation wall. Therefore, this structure could have been associated with the water supply to one of the adjacent buildings whose characteristics still need to be ascertained.Une fouille archéologique programmée, entreprise de 1998 à 2003 sur le site antique de Richeaume I (Puyloubier, Bouches-du-Rhône), a révélé la présence d'une vaste villa de plus de 5 000 m2 occupée du Ier s. av. J.-C. au début du VIe s. apr. J.-C., alimentée par un aqueduc captant les eaux de source au nord et entourée d'un certain nombre d'établissements ruraux souvent hérités du second âge du Fer. Les vestiges archéologiques mis au jour sur une superficie de 2 000 m2 correspondent aux parties résidentielle et agricole de la villa du Haut-Empire et de l'Antiquité tardive ainsi qu'à divers aménagements hydrauliques : bassins d'agrément, canalisations, égouts, murs de digue, drains et vestiges d'aqueducs. L'étude proposée ici porte sur les structures hydrauliques découvertes par la prospection géophysique et les fouilles archéologiques sur le versant oriental du site entre 315,94 et 314,05 m d'altitude. Parmi ces structures (mur de digue, paléochenal, tronçons d'aqueduc) se distinguent plus particulièrement les vestiges d'un aqueduc qui ne peut être mis en relation avec l'alimentation en eau des parties résidentielle et agricole de la villa situées plus en amont. Cet ouvrage, dont la pente à forte déclivité a nécessité la construction d'une imposante substruction, pourrait être associé à l'alimentation en eau d'un des bâtiments voisins dont la nature reste à définir