Search results for " Biochemistry"

Eco-genetics of desiccation resistance in Drosophila.

2021

International audience; Climate change globally perturbs water circulation thereby influencing ecosystems including cultivated land. Both harmful and beneficial species of insects are likely to be vulnerable to such changes in climate. As small animals with a disadvantageous surface area to body mass ratio, they face a risk of desiccation. A number of behavioural, physiological and genetic strategies are deployed to solve these problems during adaptation in various Drosophila species. Over 100 desiccation-related genes have been identified in laboratory and wild populations of the cosmopolitan fruit fly Drosophila melanogaster and its sister species in large-scale and single-gene approaches…

'Palaeoshellomics' reveals the use of freshwater mother-of-pearl in prehistory

2019

The extensive use of mollusc shell as a versatile raw material is testament to its importance in prehistoric times. The consistent choice of certain species for different purposes, including the making of ornaments, is a direct representation of how humans viewed and exploited their environment. The necessary taxonomic information, however, is often impossible to obtain from objects that are small, heavily worked or degraded. Here we propose a novel biogeochemical approach to track the biological origin of prehistoric mollusc shell. We conducted an in-depth study of archaeological ornaments using microstructural, geochemical and biomolecular analyses, including ‘palaeoshellomics’, the first…

Der Zellkern - eine Stadt in der Zelle

2016

Gespeicherte genetische Information allein nutzt nichts, wenn sie nicht zur richtigen Zeit und am richtigen Ort abgerufen werden kann. Die Verpackung der DNA im Chromatin des Zellkerns und dessen dynamische, raum-zeitliche Anordnung haben einen entscheidenden Einfluss auf die Genexpression und weitere Funktionen des Zellkerns. In dieser Ubersichtsarbeit beschreiben die Verfasser die Entwicklung der experimentellen Zellkernarchitektur-Forschung und die damit einhergehenden Veranderungen der Vorstellungen zur funktionellen Organisation des Zellkerns.

IAP et cancer : le NO contre-attaque

2021

Dans le cadre du Master 2 de l’université EPHE-PSL (Master Sciences du vivant, cursus IMaGHE, parcours Physiopathologie intégrative [PPI]), des étudiants se sont confrontés à la rédaction d’une nouvelle scientifique. Ces étudiants ayant choisi une spécialisation en cancérologie, l’équipe pédagogique leur a proposé de faire une synthèse d’articles sur deux thématiques : 1) les protéines IAP et un mécanisme original de régulation de leur activité par S-nitrosylation et 2) la séparase, dont un article paru récemment dans Nature montre qu’elle jouerait un rôle inattendu dans la protection des cellules contre la transformation tumorale. Organisés en binôme ou trinôme, les étudiants ont rédigé de…

Zilienabhängige RPE-Zellentwicklung und der WNT-Signalweg

2020

ZusammenfassungDas retinale Pigmentepithel (RPE) ist eine hochpolarisierte Einzelschicht quaderförmiger Epithelzellen, die dicht mit Melanin gepackt sind. Sie liegt zwischen den lichtempfindlichen Außensegmenten der Photorezeptoren und der Aderhaut (Choroidea), spielt eine essenzielle Rolle bei der Entwicklung der Photorezeptoren und übernimmt wichtige Funktionen in Bezug auf Nährstoffversorgung und Erhaltung, im Retinalstoffwechsel und bei der Abschirmung von der Blutversorgung der Aderhaut. Die Photorezeptoren durchlaufen täglich einen Erneuerungsprozess, bei dem 10% der äußeren Segmente durch das retinale Pigmentepithel phagozytiert werden. Dies erfordert eine enge Wechselwirkung zwische…

2019

Integral membrane proteins of the aquaporin family facilitate rapid water flux across cellular membranes in all domains of life. Although the water-conducting pore is clearly defined in an aquaporin monomer, all aquaporins assemble into stable tetramers. In order to investigate the role of protomer–protomer interactions, we analyzed the activity of heterotetramers containing increasing fractions of mutated monomers, which have an impaired oligomerization propensity and activity. In order to enforce interaction between the protomers, we designed and analyzed a genetically fused homotetramer of GlpF, the aquaglyceroporin of the bacterium Escherichia coli (E. coli). However, increasing fractio…

Spectrophotometric study of DNA interactions with ftorafur and its elementoorganic derivatives

2017

ABSTRACTFtorafur is an antimetabolite antitumour drug successfully used for treatment of various tumours. It is generally accepted that ftorafur is converted to 5-fluoruracil. However, some data indicate direct interactions of the compound with DNA. To test this hypothesis we have performed spectrophotometric study of DNA interactions of ftorafur and some of its elementoorganic derivatives with DNA. UV-VIS spectra of the tested compounds were recorded in absence and presence of increasing amounts of DNA. DNA caused a hypochromic effect in spectra of ftorafur, similar, but weaker effect was observed in 5-fluoruracil spectra. Trimethylgermyl derivative of ftorafur manifested a higher DNA-bind…

Assembly of Transmembrane b-Type Cytochromes and Cytochrome Complexes

2016

Cytochromes are involved in charge-transfer reactions, and many cytochromes contain a transmembrane domain and are part of membrane-localized electron transfer chains. Protoporphyrin IX (heme b) is the first heme product in the tetrapyrrole/heme biosynthesis pathway. In contrast to c-type cytochromes, there is no need for a specialized machinery catalyzing covalent attachment of the heme molecule to a b-type apo-cytochrome, nor is the cofactor further modified, as in a-, d- and o-type cytochromes. Thus, formation of a holo-cytochrome is relatively simple for b-type cytochromes, and this class of proteins probably represents the most ancient members of transmembrane cytochromes. However, ass…

2018

ABC (ATP binding cassette) transporters, ubiquitous in all kingdoms of life, carry out essential substrate transport reactions across cell membranes. Their transmembrane domains bind and translocate substrates and are connected to a pair of nucleotide binding domains, which bind and hydrolyze ATP to energize import or export of substrates. Over four decades of investigations into ABC transporters have revealed numerous details from atomic-level structural insights to their functional and physiological roles. Despite all these advances, a comprehensive understanding of the mechanistic principles of ABC transporter function remains elusive. The human multidrug resistance transporter ABCB1, al…

Echovirus 1 internalization negatively regulates epidermal growth factor receptor downregulation

2016

We have demonstrated previously that the human picornavirus Echovirus 1 (EV1) triggers an infectious internalization pathway that follows closely, but seems to stay separate, from the epidermal growth factor receptor (EGFR) pathway triggered by epidermal growth factor (EGF). Here, we confirmed by using live and confocal microscopy that EGFR and EV1 vesicles are following intimately each other but are distinct entities with different degradation kinetics. We show here that despite being sorted to different pathways and located in distinct endosomes, EV1 inhibits EGFR downregulation. Simultaneous treatment with EV1 and EGF led to an accumulation of EGFR in cytoplasmic endosomes, which was evi…