We report the identification, functional expression, purification, reconstitution and electrophysiological characterization of an up to now unique prokaryotic potassium ion channel (KcsA

Ceramides draw wide attention as tumor suppressor lipids that act directly on mitochondria to trigger apoptotic cell death. However, molecular details of the underlying mechanism are largely unknown. Using a photoactivatable ceramide probe, we here identify the voltage-dependent anion channels VDAC1 and VDAC2 as mitochondrial ceramide binding proteins. Coarse-grain molecular dynamics simulations reveal that both channels harbor a ceramide binding site on one side of the barrel wall. This site includes a membrane-buried glutamate that mediates direct contact with the ceramide head group. Substitution or chemical modification of this residue abolishes photolabeling of both channels with the ceramide probe. Unlike VDAC1 removal, loss of VDAC2 or replacing its membrane-facing glutamate with glutamine renders human colon cancer cells largely resistant to ceramide-induced apoptosis. Collectively, our data support a role of VDAC2 as direct effector of ceramide-mediated cell death, providing a molecular framework for how ceramides exert their anti-neoplastic activity.

Previous studies have suggested a role for c-fos in cellular differentiation in fetal membranes, haematopoietic cells and teratocarcinoma stem cells. In other cell types, such as fibroblasts, c-fos expression is normally very low, but is rapidly induced by peptide growth factors, implicating c-fos in growth control mechanisms. Here, we show that the TPA (12-O-tetradecanoylphorbol-13-acetate)-induced macrophage-like differentiation of HL60 human promyelocytic precursor cells is accompanied by the induction of both c-fos mRNA and protein within 15 min after treatment, suggesting a functional role for c-fos in this differentiation system. In quiescent terminally differentiated macrophages, expression of c-fos is inducible by the macrophage-specific growth factor colony-stimulating factor-1 (CSF-1). The kinetics of c-fos induction, however, are entirely different from those in growth factor-stimulated fibroblasts, supporting the view that the c-fos gene product may serve different functions in different cell types.

During early stages of growth, Streptomyces reticuli synthesizes a hyphaeassociated, haem-containing enzyme which exhibits catalase and peroxidase activities with broad substrate specificity (CpeB). The purified dimeric enzyme (160 kDa) consists of two identical subunits. Using anti-CpeB antibodies and an expression-as well as a mini-library, the corresponding cpeB gene was identified and sequenced. It encodes a protein of 740 aa with a molecular mass of 81.3 kDa. The deduced protein shares the highest level of amino acid identity with KatG from Caulobacter crescentus and Mycobacterium tuberculosis, and PerA from Bacillus stearothermophilus. Streptomyces lividans transformants carrying cpeB and the upstream-located furs gene with its regulatory region on the bifunctional vector pWHM3 produced low or enhanced levels of CpeB in the presence or absence of Fe ions, respectively. An in-frame deletion of the major part of furs induces increased CpeB synthesis. The data imply that Furs regulates the transcription of cpeB. The deduced Furs protein is rich in histidine residues, contains a putative N-terminally situated helix-turn-helix motif and has a molecular mass of 15.1 kDa. It shares only 29% amino acid identity with the Escherichia coli ferric uptake regulator (Fur) protein, but about 64% with FurA deduced from the genomic sequences of several mycobacteria. The predicted secondary structures of Furs and FurA are highly similar and considerably divergent from those of the E. coli Fur. In contrast to some Gram-negative bacteria, within several mycobacteria an intact furA gene or a furA pseudogene is upstream of a catalase-peroxidase (katG) gene predicted to encode a functional or a non-functional (Mycobacterium leprae) enzyme. Thus the data obtained for Streptomyces reticuli are expected to serve as an additional model to elucidate the regulation of mycobacterial catalase-peroxidase genes.1

The role of memory in visual search has lately become a controversial issue. Horowitz and Wolfe (1998) observed that performance in a visual search task was little affected by whether the stimuli were static or randomly relocated every 111 ms. Because a memory-based mechanism, such as inhibition of return, would be of no use in the dynamic condition, Horowitz and Wolfe concluded that memory is likewise not involved in the static condition. However, Horowitz and Wolfe could not effectively rule out the possibility that observers adopted a different strategy in the dynamic condition than in the static condition. That is, in the dynamic condition observers may have attended to a subregion of the display and waited for the target to appear there (sit-and-wait strategy). This hypothesis is supported by experimental data showing that performance in their dynamic condition does not differ from performance in another dynamic condition in which observers are forced to adopt a sit-and-wait strategy by being presented with a limited region of the display only.

H pylori infection is associated with growth delay, growth retardation, or both in affected children.

Herpes simplex virus (HSV) can perturb the function of dendritic cells (DC). The underlying mechanisms are not defined. In the present study we demonstrate that HSV induces a substantial number of immature DC to undergo apoptosis by a mechanism involving caspase-8. We found strongly enhanced expression of TNF- § and TRAIL but not CD95 ligand after HSV infection. Blocking experiments suggested that these classical death ligands contribute to HSV-induced cell death of immature DC. Because uninfected DC are resistant to the apoptosis-inducing effect of death ligands we searched for a viral "competence-to-die" signal. Further analysis revealed that HSV-infected immature DC down-regulate long cellular FLICE-inhibitory protein (c-FLIP L ) and up-regulate p53 whereas other apoptosis-regulating proteins (e.g. Bcl-2, RIP, FADD) were not affected. Down-regulation of c-FLIP L was not due to diminished gene transcription or reduced mRNA stability because the level of c-FLIP L mRNA was rather increased. Moreover, down-regulation of c-FLIP L could not be blocked by the anti-herpetic drug acyclovir. Finally, the underlying mechanism was also operative in human umbilical vein endothelial cells, which show a similar susceptibility to HSV infection and strength of c-FLIP L expression. These results suggest that HSV targets c-FLIP L protein in immature DC and other infectable cells to disrupt their function.

A field experiment was conducted in which carbon tetrachloride (CT) was found to transform to chloroform (CF) and carbon disulfide (CS2) in a ratio of about 2:1. Subsequent laboratory work was undertaken to better define the conditions required for this product ratio and to investigate its use as a means of distinguishing biologically driven and abiotic transformations in aquifers. The field experiment was conducted to assess the efficacy of a bioremediation scheme for treating CT in groundwater. The test section of the aquifer was taken to sulfate reducing conditions by the periodic addition of acetate from a nutrient injection wall (NIW). Under these conditions, CT was observed to transform completely producing primarily CF and CS2 at a ratio of approximately 2:1. In laboratory columns designed to mimic the field conditions, low-input concentrations of CT (<70 μg/L) resulted in complete dechlorination of the molecule, while higher input concentrations (>400 μg/L) led to the production of CF and CS2 in the same ratio as observed in the field. It was determined that amorphous iron sulfide had precipitated on the sand grains during the column experiments. Stertile laboratory batch experiments were conducted to test CT reactivity with various iron sulfide solids. A narrow ratio of 2:1 ± 0.4 CF to CS2 was only observed for CT reacting with freshly precipitated, amorphous FeS in near pH neutral solutions. The 2:1 ratio may be a useful tool for distinguishing abiotic transformations from biodegradation in sulfate reducing environments where FeS is actively precipitated.