Instability of bacteriophage Mu transposase and the role of host Hfl protein

The activity of the transposase of bacteriophage Mu is unstable, requiring the protein to be synthesized throughout the lytic cycle (Pato and Reich, 1982). Using Western blot analysis, we analysed the stability of the transposase protein during the lytic cycle and found that it, too, is unstable. The instability of the protein is observed both in the presence and the absence of Mu DNA replication, and is independent of other Mu-encoded proteins and the transposase binding sites at the Mu genome ends. Stability of the protein is enhanced in host strains mutated at the hfl locus; however, stability of the transposase activity is not enhanced in these strains, suggesting that functional inactivation of the protein is not simply a result of its proteolysis.     

Partial characterization of cell wall from a flocculent strain ofKluyveromyces marxianus

Summary Cell walls from aKluyveromyces marxianus either non flocculent or flocculent strain were isolated and analysed for protein, carbohydrates and phosphate content. Alkaline extract of proteins were analysed by SDS-PAGE. The results revealed a higher protein content in the cell walls from the flocculent strain. Electrophoresis of the cell wall proteins of the flocculent strain showed an extra peptide with an apparent molecular weight of 37 KDa which is absent fom non-flocculent cells. The involvement of this protein in cell adhesion during flocculation is discussed.     

Unusual DNA structures at the integration site of an HIV provirus

Supercoiled pHXBc2 DNA (containing the genome of the human immunodeficiency virus type 1 and human sequences) migrated more slowly than linear DNA in native and ethidium bromide agarose gel electrophoresis at 4.5 volts/cm, suggesting the presence of unusual DNA structures. S1 nuclease analysis of pHXBc2 revealed two S1 hypersensitive sites. Site I was located within a 25 bp direct repeat in host DNA 0.6 kB upstream from the 5' LTR. Site II was mapped 0.2 kB upstream from the vif gene start site. Sequence analysis showed that Site I sequences could assume different unusual DNA structures, whereas sequences at Site II could assume either slipped or H-DNA forms. Unusual DNA structures in host DNA may be associated with active chromatin regions and may favor proviral integration.     

Molecular analysis of the nuclear organellar genotype of somatic hybrid plants between tomato (Lycopersicon esculentum) and Lycopersicon chilense

Summary Somatic hybrid plants were recovered following fusion of leaf mesophyll protoplasts isolated from tomato (Lycopersicon esculentum) cultivar UC82 with protoplasts isolated from suspension cultured cells of L. chilense, LA 1959. Iodoacetate was used to select against the growth of unfused tomato protoplasts. Two somatic hybrids were recovered in a population of 16 regenerants. No tomato regenerants were recovered; all of the non-hybrid regenerants were L. chilense. The L. chilense protoplast regenerants were tetraploid. The hybrid nature of the plants was verified using species-specific restriction fragment length polymorphisms for the nuclear, chloroplast and mitochondrial genomes. The somatic hybrids had inherited the chloroplast DNA of the tomato parent, and portions of the mitochondrial DNA of the L. chilense parent. The somatic hybrids formed flowers and developed seedless fruit.     

Lipotropha dorci n. sp. [Neogregarinida], parasite des larves deDorcus parallelipipedus L. [Coleopt. scarab.]

Résumé Des larves deDorcus parallelipipedus L. provenant de Saint-Hilaire-de-Brethmas (Gard) dans la région méditerranéenne de France et récoltées dans des troncs décomposés de chataigniers, se sont révélées intensément parasitées par des Grégarines appartenant à l'ordre desNeogregarinida. Nous étudions leur localisation dans le tissu adipeux, leur cycle, l'action pathogène sur l'h?te et discutons leur place systématique.

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Summary Lipotropha dorci n. sp. (Neogregarinida) is a parasite developing inDorcus parallelepipedus. The parasite is situated only in the fat body which can be destroyed completely by its activity. The life cycle ofLipotropha includes only one type of schizogony with 3–4 μ long merozo?ts, the spherical uninucleate gametocytes are gathered in pairs and form 23 μ long gametokysts. These give rise to 11 to 12 μ long sporocysts with a thick, non ornamented envelope, gathered round rests of cytoplasma. The size of these different stages enables to distinguishLipotropha dorci from the already described species:Lipotropha macrospora Keilin andLipotropha microspora Keilin.

     

Characterization of amber mutations in bacteriophage Mu transposase: a functional analysis of the protein

We have characterized a series of amber mutations in the A gene of bacteriophage Mu encoding the phage transposase. We tested different activities of these mutant proteins either in a sup0 strain or in different sup bacteria. In conjunction with the results described in the accompanying paper by Bétermier et al. (1989) we find that the C-terminus of the protein is not absolutely essential for global transposase function, but is essential for phage growth. Specific binding to Mu ends is defined by a more central domain. Our results also reinforce the previous findings (Bétermier et al., 1987) that more than one protein may be specified by the A gene.     

Through-bond electron-transfer interaction in proteins

A model for the through-bond electronic interaction between electron donor and acceptor in proteins is developed. We use a one-electron Hamiltonian, write the Dyson's equation in site representation and solve it by using a Green's function formalism with some renormalization ideas. An expression for Tab which describes the exponential decay with distance bond per bond is obtained. Covalent, non-covalent and convergent pathways are considered and no periodic approximation is needed.     

Interfacial and micellar behavior of glucose lipid

Summary Glucose lipid of notable surfactant properties was produced by using hydrocarbon assimilating bacterium of the bacterial strain MM1. Its surface active properties were notable in spite of ,-hydrophilic and bulky molecule. The critical micelle concentration (cmc) was small (0.165 M); surface and interfacial tension for hexadecane at 0.1 % (pH 7.35) solution, 24.6 and 13.3 mN/m, respectively. The emulsifying action was excellent and comparable to those of rhamnolipids. The micelle has the outer radius. 28.5 Å and inner core, 6.7 Å on the basis of the concentric spherical shell model by means of the small angle X-ray solution scattering measurement.Dedicated to Professor Fritz Wagner on the occasion of his 65th birthday.     

CX3CL1 induces cell migration and invasion through ICAM-1 expression in oral squamous cell carcinoma cells

Human oral squamous cell carcinoma (OSCC) has been associated with a relatively low survival rate over the years and is characterized by a poor prognosis. C-X3-C motif chemokine ligand 1 (CX3CL1) has been involved in advanced migratory cells. Overexpressed CX3CL1 promotes several cellular responses related to cancer metastasis, including cell movement, migration and invasion in tumour cells. However, CX3CL1 controls the migration ability, and its molecular mechanism in OSCC remains unknown. The present study confirmed that CX3CL1 increased cell movement, migration and invasion. The CX3CL1-induced cell motility is upregulated through intercellular adhesion molecule-1 (ICAM-1) expression in OSCC cells. These effects were significantly suppressed when OSCC cells were pre-treated with CX3CR1 monoclonal antibody (mAb) and small-interfering RNA (siRNA). The CX3CL1-CX3CR1 axis activates promoted PLCβ/PKCα/c-Src phosphorylation. Furthermore, CX3CL1 enhanced activator protein-1 (AP-1) activity. The CX3CR1 mAb and PLCβ, PKCα, c-Src inhibitors reduced CX3CL1-induced c-Jun phosphorylation, c-Jun translocation into the nucleus and c-Jun binding to the ICAM-1 promoter. The present results reveal that CX3CL1 induces the migration of OSCC cells by promoting ICAM-1 expression through the CX3CR1 and the PLCβ/PKCα/c-Src signal pathway, suggesting that CX3CL1-CX3CR1-mediated signalling is correlated with tumour motility and appealed to be a precursor for prognosis in human OSCC.     

Calorific values of Chlorella vulgaris (Trebouxiophyceae) as a function of different phosphorus concentrations

Quantification of the calorific content of microalgae is critical in studies of energy flow, trophic partitioning, plant/herbivore interactions in aquaculture and biomass production for biofuels. We investigated the calorific value and biochemical composition of Chlorella vulgaris at different phosphorus (P) concentrations (6.0 × 10^?7, 2.3 × 10^?6 and 2.3 × 10^?4 mol L^?1 P). As expected, the control (2.3 × 10^?4 mol L^?1 P) supported better growth than P limited treatments. Biomolecules like total carbohydrates and lipids accumulated under P limitation, which significantly correlated with high calorific values. Lipid class composition showed that triacylglycerols were the most accumulated under P limited conditions. The calorific value reported under control conditions (13.78 kJ g^?1) was less than those obtained under P limitation (30.47–33.07 kJ g^?1). The highest calorific value with less growth retardation was obtained at 2.3 × 10^?6 mol L^?1 P.