The Tripartite Type III Secreton of Shigella flexneri Inserts Ipab and Ipac into Host Membranes

Bacterial type III secretion systems serve to translocate proteins into eukaryotic cells, requiring a secreton and a translocator for proteins to pass the bacterial and host membranes. We used the contact hemolytic activity of Shigella flexneri to investigate its putative translocator. Hemolysis was caused by formation of a 25-Å pore within the red blood cell (RBC) membrane. Of the five proteins secreted by Shigella upon activation of its type III secretion system, only the hydrophobic IpaB and IpaC were tightly associated with RBC membranes isolated after hemolysis. Ipa protein secretion and hemolysis were kinetically coupled processes. However, Ipa protein secretion in the immediate vicinity of RBCs was not sufficient to cause hemolysis in the absence of centrifugation. Centrifugation reduced the distance between bacterial and RBC membranes beyond a critical threshold. Electron microscopy analysis indicated that secretons were constitutively assembled at 37°C before any host contact. They were composed of three parts: (a) an external needle, (b) a neck domain, and (c) a large proximal bulb. Secreton morphology did not change upon activation of secretion. In mutants of some genes encoding the secretion machinery the organelle was absent, whereas ipaB and ipaC mutants displayed normal secretons

International Journal of Medical Microbiology: Editorial

SCOPUS: ed.jinfo:eu-repo/semantics/publishe

Identification et structure de domaines peptidiques de la toxine diphtérique impliqués dans son interaction avec la membrane lipidique

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

pH-sensitive toxins: interactions with membrane bilayers and application to drug delivery.

pH-sensitive toxins are secreted by bacteria and reach the cytosol of eukaryotic target cells by complex mechanisms involving receptor binding, membrane interaction and translocation across a cell lipid membrane. Membrane interaction and ability to reach the cytoplasm have been used respectively to present proteins at the cell surface and to transport foreign peptides or DNA into the cytoplasm. The first approach is used in anticancer vaccination and the second in inducing a major histocompatibility (MHC) class I presentation of exogenous peptides or proteins. A brief overview of the use of toxins themselves for targeting cancer cells is also presented. Altogether, the data suggest that pH sensitive toxins have a huge potential for surface presentation or cytosol transport of biomacromolecules and that many ways could still be explored to develop new strategies in vaccination or therapeutic methods.Journal ArticleReviewSCOPUS: re.jinfo:eu-repo/semantics/publishe

Translocation des toxines bactériennes au travers d'une membrane cellulaire :caractérisation des paramètres physico-chimiques et structuraux impliqués dans le passage de la forme soluble à la forme membranaire et détermination de la topologie protéique

Doctorat en SciencesThèse d'agrégationinfo:eu-repo/semantics/nonPublishe

Managing research careers in an expanding research profile Université Libre de Bruxelles, Belgium

The University is undergoing major changes, as it is faced with several challenges, whilst the expectations of its partners about the missions it should pursue are rising. It is also undergoing major changes in management and governance methods imposed by financial restrictions from the public sector (F. Thys-Clément, 1995). Consequently, the University as an institution is facing a major paradigm transformation expressed in particular by the notion of "academic capitalism" stressed by the American scholars L. Leslie and Sh. Slaughter (1997). The French-speaking Belgian universities are in the midst of reorganising the way they operate because they are confronted with financial restrictions brought about by the implementation of budgetary federalism (B. Bayonet and F. Thys-Clémént, 1998) which effects mainly the French speaking community - Brussels. Our paper deals with the organisational arrangement of contractual research at the (French-speaking) Université Libre de Bruxelles (ULB), the financial volume of which has virtually tripled in the last fifteen years. (R. Tollet, 2002). The first chapter of this article will briefly cover the integration of research in Belgium in an international context. The place of the ULB in the Belgian academic landscape and, in particular, that of the Communauté française de Belgique (here after referred to as French speaking community) will then be broached, followed by the specific organisational arrangements of contractual research. The conclusion will underscore the need for a strategic implementation of this modus operandi for the University.SCOPUS: ch.binfo:eu-repo/semantics/publishe

Secondary structure of sea anemone cytolysins in soluble and membrane bound form by infrared spectroscopy.

Attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) was used to investigate the secondary structure of two pore-forming cytolysins from the sea anemone Stichodactyla helianthus and their interaction with lipid membranes. Frequency component analysis of the amide I' band indicated that these peptides are composed predominantly of beta structure, comprising 44-50% beta-sheet, 18-20% beta-turn, 12-15% alpha-helix, and 19-22% random coil. Upon interaction with lipid membranes a slight increase in the alpha-helical and beta-sheet structures was observed with a concomitant decrease of the unordered structure. Polarisation experiments indicated that both toxins had some disordering effect on the lipid layers. The dichroic ratio of the alpha-helical component of the membrane-bound toxin was 3.0-3.3, indicating that this element was oriented with an angle of 38 degrees-42 degrees with respect to the normal to the plane of the crystal surface, thus resulting almost parallel to the mean direction of the lipid chains.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Determination of soluble and membrane protein structure by Fourier transform infrared spectroscopy. II. Experimental aspects, side chain structure, and H/D exchange.

Journal ArticleReviewinfo:eu-repo/semantics/publishe

Polarized Attenuated Total Reflection Infrared Spectroscopy as a tool the structure and orientation of amphipathic peptides in a lipid bilayer

info:eu-repo/semantics/publishe

Diphtheria Toxin - lipid interactions: Fusion of lipid vesicles at low pH

info:eu-repo/semantics/publishe