Broadened Substrate Specificity of 3-Hydroxyethyl Bacteriochlorophyllide a Dehydrogenase (BchC) Indicates a New Route for the Biosynthesis of Bacteriochlorophyll a

Bacteriochlorophyll a biosynthesis requires formation of a 3-hydroxyethyl group on pyrrole ring A that gets subsequently converted into a 3-acetyl group by 3-vinyl bacteriochlorophyllide a hydratase (BchF) followed by 3-hydroxyethyl bacteriochlorophyllide a dehydrogenase (BchC). Heterologous overproduction of Chlorobaculum tepidum BchF revealed an integral transmembrane protein that was efficiently isolated by detergent solubilization. Recombinant C. tepidum BchC was purified as a soluble protein-NAD⁺ complex. Substrate recognition of BchC was investigated using six artificial substrate molecules. Modification of the isocyclic E ring, omission of the central magnesium ion, zinc as an alternative metal ion, and a non-reduced B ring system were tolerated by BchC. According to this broadened in vitro activity, the chlorin 3-hydroxyethyl chlorophyllide a was newly identified as a natural substrate of BchC in a reconstituted pathway consisting of dark-operative protochlorophyllide oxidoreductase, BchF, and BchC. The established reaction sequence would allow for an additional new branching point for the synthesis of bacteriochlorophyll a. Biochemical and site-directed mutagenesis analyses revealed, in contrast to theoretical predictions, a zinc-independent BchC catalysis that requires NAD⁺ as a cofactor. Based on these results, we are designating a new medium-chain dehydrogenase/reductase family (MDR057 BchC) as theoretically proposed from a recent bioinformatics analysis.     

Food quantity–quality co‐limitation: Interactive effects of dietary carbon and essential lipid supply on population growth of a freshwater rotifer

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Tyrosine kinase and cooperative TGFbeta signaling in the reproductive organs of Schistosoma mansoni

Drug-induced suppression of female schistosome sexual maturation is an auspicious strategy to combat schistosomiasis since the eggs are the causative agent. The establishment of drug targets requires knowledge about the molecular mechanisms that regulate the development of the female reproductive organs, which include vitellarium and ovary. This review summarizes recent studies suggesting tyrosine kinases as important factors for the regulation of female gonad development. In this context, especially cytoplasmatic tyrosine kinases of the Src class seem to play dominant roles. Moreover, experimental data and theoretical concepts are provided supporting a crosstalk between tyrosine kinase and TGFbeta signaling in the production of vitellocytes. Finally, we take advantage from the schistosome genome project to propose a model for the regulation of vitelline-cell production and differentiation.     

New Streptococcus pneumoniae clones in deceased wild chimpanzees

In wild chimpanzees in the Ta? National Park, C?te d'Ivoire, sudden deaths which were preceded by respiratory problems had been observed since 1999. Two new clones of Streptococcus pneumoniae were identified in deceased apes on the basis of multilocus sequence typing analysis and ply, lytA, and pbp2x sequences. The findings suggest that virulent S. pneumoniae occurs in populations of wild chimpanzees with the potential to cause infections similar to those observed in humans.     

Mono-ADP-ribosylation sites of human CD73 inhibit its adenosine-generating enzymatic activity

Purinergic Signalling - CD73-derived adenosine plays a major role in damage-induced tissue responses by inhibiting inflammation. Damage-associated stimuli, such as hypoxia and mechanical stress,...     

Expression of the Stem Cell Factor Nestin in Malignant Pleural Mesothelioma Is Associated with Poor Prognosis

Background

The epithelioid and sarcomatoid histologic variants of malignant pleural mesothelioma (MPM) can be considered as E- and M-parts of the epithelial-mesenchymal transition (EMT) axis; the biphasic being an intermediate. EMT is associated with an increase of stem cell (SC) traits. We correlated the neural crest SC marker nestin and the EMT marker periostin with histology, type of neo-adjuvant chemotherapy (CT) and overall survival (OS) of MPM patients.

Patients and Methods

Tumor tissues of a historic cohort 1 (320 patients) and an intended induction chemotherapy followed by extrapleural pneumonectomy (EPP) cohort 2 (145 patients) were immunohistochemically H-scored (intensity of immunoreactivity multiplied by frequency of stained cells). Paired chemo-naïve biopsies and -treated surgical specimens were available for 105/145 patients. CT included platinum/gemcitabine (Pla/Gem) or platinum/pemetrexed (Pla/Pem).

Results

Expression of any cytosolic nestin progressively increased from epithelioid to biphasic to sarcomatoid MPM in cohort 1, whereas the diagnostic markers calretinin and podoplanin decreased. In cohort 2, Pla/Pem CT increased the expression level of nestin in comparison to Pla/Gem, whereas the opposite was found for periostin. In Pla/Pem treated patients, nestin was higher in biphasic MPM compared to epithelioid. In addition to non-epithelioid histology, any expression of nestin in chemo-naïve biopsies (median overall survival: 22 vs. 17 months) and chemo-treated surgical specimens (18 vs. 12 months) as well as high periostin in biopsies (23 vs. 15 months) were associated with poor prognosis. In the multivariate survival analysis, any nestin expression in chemo-naïve biopsies proved to be an independent prognosticator against histology. In both pre- and post-CT situations, the combination of nestin or periostin expression with non-epithelioid histology was particularly/ dismal (all p-values <0.05).

Conclusions

The SC marker nestin and the EMT marker periostin allow for further prognostic stratification among histologic variants of MPM. Their expression level is influenced by neo-adjuvant chemotherapy.     

Effect of GTP and Ca2+ on inositol 1,4,5-trisphosphate induced Ca2+ release from permeabilized rat exocrine pancreatic acinar cells

The effects of Ca2+ and GTP on the release of Ca2+ from the inositol 1,4,5-trisphosphate (IP3) sensitive Ca2+ compartment were investigated with digitonin permeabilized rat pancreatic acinar cells. The amount of Ca2+ released due to IP3 directly correlated with the amount of stored Ca2+ and was found to be inversely proportional to the medium free Ca2+ concentration. Ca2+ release induced by 0.18 microM IP3 was half maximally inhibited at 0.5 microM free Ca2+, i.e. at concentrations observed in the cytosol of pancreatic acinar cells. GTP did not cause Ca2+ release on its own, but a single addition of GTP (20 microM) abolished the apparent desensitization of the Ca2+ release which was observed during repeated IP3 applications. This effect of GTP was reversible. GTP gamma S could not replace GTP. Desensitization still occurred when GTP gamma S was added prior to GTP. The reported data indicate that GTP, stored Ca2+ and cytosolic free Ca2+ modulate the IP3 induced Ca2+ release.