Membrane specializations and endosome maturation in dendritic cells and B cells

Interest in the cell biology of antigen presentation is centered on dendritic cells (DCs) as initiators of the immune response. The ability to examine primary antigen-presenting cells, as opposed to cell lines, has opened a new window for study of antigen processing and peptide acquisition by Class II major histocompatibility complex (MHC) products, especially where intracellular trafficking of peptide-Class-II complexes is concerned. Here, we review the dynamics of Class II MHC-positive intracellular structures in dendritic cells as well as B cells. We focus on the generation of multivesicular bodies, where Class II MHC products acquire antigenic peptide, on the endosomal transport of peptide-loaded Class II MHC to the cell surface and on the importance of Class II MHC localization in membrane microdomains.     

1,2,4-Triazolo mercapto and aminonitriles as potent antifungal agents

A series of 3-mercapto-1,2,4-triazoles mono or disubstituted at 2-, 3- or 4-positions were synthesized and evaluated as antifungal agents. Many of these derivatives exhibit high activity against Candida albicans and Candida tropicalis.     

Characterization of functional oligosaccharide mimics of the Shigella flexneri serotype 2a O-antigen: implications for the development of a chemically defined glycoconjugate vaccine

Protection against reinfection with noncapsulated Gram-negative bacteria, such as Shigella, an enteroinvasive bacterium responsible for bacillary dysentery, is mainly achieved by Abs specific for the O-Ag, the polysaccharide part of the LPS, the major bacterial surface Ag. The use of chemically defined glycoconjugates encompassing oligosaccharides mimicking the protective determinants carried by the O-Ag, thus expected to induce an efficient anti-LPS Ab response, has been considered an alternative to detoxified LPS-protein conjugate vaccines. The aim of this study was to identify such functional oligosaccharide mimics of the S. flexneri serotype 2a O-Ag. Using protective murine mAbs specific for S. flexneri serotype 2a and synthetic oligosaccharides designed to analyze the contribution of each sugar residue of the branched pentasaccharide repeating unit of the O-Ag, we demonstrated that the O-Ag exhibited an immunodominant serotype-specific determinant. We also showed that elongating the oligosaccharide sequence improved Ab recognition. From these antigenicity data, selected synthetic oligosaccharides were assessed for their potential to mimic the O-Ag by analyzing their immunogenicity in mice when coupled to tetanus toxoid via single point attachment. Our results demonstrated that induction of an efficient serotype 2a-specific anti-O-Ag Ab response was dependent on the length of the oligosaccharide sequence. A pentadecasaccharide representing three biological repeating units was identified as a potential candidate for further development of a chemically defined glycoconjugate vaccine against S. flexneri 2a infection.     

Specificity of action on mosquito larvae of Bacillus thuringiensis israelensis toxins encoded by two different genes

Summary A 135 kDa protein gene and two open reading frames (ORF1 and ORF2) have been cloned from a large plasmid of Bacillus thuringiensis israelensis (Bourgouin et al. 1986). The Escherichia coli recombinant clones containing these genes were highly toxic to larvae of Aedes aegypti, Anopheles stephensi and Culex pipiens. From subcloning experiments it was deduced that the 135 kDa polypeptide alone was responsible for the toxic activity on both A. aegypti and An. stephensi larvae. In contrast, the presence of two polypeptides, the 135 kDa protein and the ORF1 product was required for toxicity to C. pipiens larvae. The minimal toxic fragment of the 135 kDa polypeptide has been delineated. The results indicate that a polypeptide of about 65 kDa, corresponding to an amino-terminal part of the 135 kDa protein is sufficient for toxicity. Sequence comparisons indicate that the ORF1 product may correspond to an N-terminal part of a rearranged 130 kDa protein.     

Sur la morphologie externe et interne de Rotorboides granulosa (Heron-Allen & Earland) emendation du genre Rotorboides Sellier de Civrieux, 1977 (Foraminiferida)

Discorbis valvulata granulosa HERON-ALLEN and EARLAND, which has been found by the present authorsin the recent deposits of Watamu beach (Kenya), is the type-species of the genus RotorboidesSELLIER de CIVRIEUX, 1977. The study of this species has permitted to describe in detail its outer and inner morphology, to discuss its previous assignments (Discorbis, Rotorbinella) and to emend the genus Rotorboides.     

Contribution à l'étude de la microfaune des récifs messiniens d'Oranie Occidentale (Algérie)

Benthonic Foraminifera and Ostracoda from the reefal Messinian of Western Oranie (Algeria) belong partly to species already known in the mediterranean Tortonian and Pliocene and partly as far as Ostracoda are concerned to new species. These last ones are perhaps in connection with the reef facies they could characterized all around the Mediterranean Sea.     

Respective role of the 42- and 51-kDa components of the Bacillus sphaericus toxin overexpressed in Bacillus thuringiensis

Abstract The 42- and 51-kDa protein genes of Bacillus sphaericus 1593 have been subcloned independently downstream from the cytA gene promoter of Bacillus thuringiensis serovar israelensis and introduced into a non-mosquitocidal strain of Bacillus thuringiensis . Consequently, each protein was overproduced and accumulated as inclusion bodies which were purified. For the first time, the 42-kDa protein inclusions alone were found to be toxic to Culex pipiens larvae (LC₅₀ at 48 h 300 ng ml⁻¹); in contrast, the 51-kDa protein inclusions were not. Moreover, a synergistic effect between these two components was observed.     

The Doubly Phosphorylated Form of HPr, HPr(Ser-P)(His～P), Is Abundant in Exponentially Growing Cells of Streptococcus thermophilus and Phosphorylates the Lactose Transporter LacS as Efficiently as HPr(His～P)

In Streptococcus thermophilus, lactose is taken up by LacS, a transporter that comprises a membrane translocator domain and a hydrophilic regulatory domain homologous to the IIA proteins and protein domains of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The IIA domain of LacS (IIA^LacS) possesses a histidine residue that can be phosphorylated by HPr(His~P), a protein component of the PTS. However, determination of the cellular levels of the different forms of HPr, namely, HPr, HPr(His~P), HPr(Ser-P), and HPr(Ser-P)(His~P), in exponentially lactose-growing cells revealed that the doubly phosphorylated form of HPr represented 75% and 25% of the total HPr in S. thermophilus ATCC 19258 and S. thermophilus SMQ-301, respectively. Experiments conducted with [³²P]PEP and purified recombinant S. thermophilus ATCC 19258 proteins (EI, HPr, and IIA^LacS) showed that IIA^LacS was reversibly phosphorylated by HPr(Ser-P)(His~P) at a rate similar to that measured with HPr(His~P). Sequence analysis of the IIA^LacS protein domains from several S. thermophilus strains indicated that they can be divided into two groups on the basis of their amino acid sequences. The amino acid sequence of IIA^LacS from group I, to which strain 19258 belongs, differed from that of group II at 11 to 12 positions. To ascertain whether IIA^LacS from group II could also be phosphorylated by HPr(His~P) and HPr(Ser-P)(His~P), in vitro phosphorylation experiments were conducted with purified proteins from Streptococcus salivarius ATCC 25975, which possesses a IIA^LacS very similar to group II S. thermophilus IIA^LacS. The results indicated that S. salivarius IIA^LacS was phosphorylated by HPr(Ser-P)(His~P) at a higher rate than that observed with HPr(His~P). Our results suggest that the reversible phosphorylation of IIA^LacS in S. thermophilus is accomplished by HPr(Ser-P)(His~P) as well as by HPr(His~P).     

Reactive complexes in myoglobin and nitric oxide synthase

In this overview some of our crystallographic and spectroscopic studies on reactive complexes in myoglobin and nitric oxide synthase are summarised. Myoglobin and nitric oxide synthase are both haemoproteins with some similar reaction intermediates. For myoglobin we have studied different intermediates generated in the reaction with hydrogen peroxide by X-ray diffraction, single-crystal microspectrophotometry, electron paramagnetic resonance spectroscopy, Mössbauer spectroscopy, resonance Raman spectroscopy and quantum refinement. Several of these myoglobin states are quite susceptible to radiation-induced changes during crystallographic data collection, and we have observed a radiation-induced change of the ferric resting myoglobin to aqua ferrous myoglobin, of myoglobin compound II to a proposed intermediate H, and of myoglobin compound III to peroxy myoglobin. For the myoglobin compound II/ intermediate H we observe a single-bonded Fe^IV-O species, which is probably protonated. The long Fe-O bond seen in the crystal structure can be supported by the observation of a new ¹⁸O-sensitive resonance Raman mode at 687 cm⁻¹. For nitric oxide synthase we detected with cryobiochemical methods in electron paramagnetic resonance spectra the first biopterin radical serving as electron donor to the ferrous-oxy complex, and that biopterin serves as a proton donor as well, in addition we could observe formation of the Fe(NO) complex with a amino-pterin cofactor capable to form a reactive radical.