Spectrophotometric identification of 8-hydroxy-5-deazaflavin: NADPH oxidoreductase activity in streptomycetes producing tetracyclines

Abstract Cell-free extracts of vegetative mycelia of Streptomyces aureofaciens and Streptomyces rimosus were found to reduce streptomycete-origin 8-hydroxy-5-deazaisoalloxazine derivatives (SF₄₂₀) using NADPH as a dnor of hydrogen and electrons. 7,8-didemethyl-8-hydroxy-5-deazariboflavin (F₀) also was a substrate, although with a lower reaction rate than that for SF₄₂₀. NADH could not substitute for NADPH. The F₄₂₀-reductase activity was also observed in homogenates of S. aureofaciens spores.     

Unique organization of photosystem II supercomplexes and megacomplexes in Norway spruce

Photosystem II (PSII) complexes are organized into large supercomplexes with variable amounts of light‐harvesting proteins (Lhcb). A typical PSII supercomplex in plants is formed by four trimers of Lhcb proteins (LHCII trimers), which are bound to the PSII core dimer via monomeric antenna proteins. However, the architecture of PSII supercomplexes in Norway spruce[Picea abies (L.) Karst.] is different, most likely due to a lack of two Lhcb proteins, Lhcb6 and Lhcb3. Interestingly, the spruce PSII supercomplex shares similar structural features with its counterpart in the green alga Chlamydomonas reinhardtii [Kou?il et al. (2016) New Phytol. 210 , 808–814]. Here we present a single‐particle electron microscopy study of isolated PSII supercomplexes from Norway spruce that revealed binding of a variable amount of LHCII trimers to the PSII core dimer at positions that have never been observed in any other plant species so far. The largest spruce PSII supercomplex, which was found to bind eight LHCII trimers, is even larger than the current largest known PSII supercomplex from C. reinhardtii. We have also shown that the spruce PSII supercomplexes can form various types of PSII megacomplexes, which were also identified in intact grana membranes. Some of these large PSII supercomplexes and megacomplexes were identified also in Pinus sylvestris, another representative of the Pinaceae family. The structural variability and complexity of LHCII organization in Pinaceae seems to be related to the absence of Lhcb6 and Lhcb3 in this family, and may be beneficial for the optimization of light‐harvesting under varying environmental conditions.     

Effect of tetracycline derivatives and some cations on the activity of anhydrotetracycline oxygenase

Biotechnology Letters - Anhydrotetracycline oxygenase was partially purified on a Sephadex G-25 column and DEAE-cellulose. The purified enzyme was inhibited by tetracycline derivatives added to the...     

Genetic improvement of glucose isomerase production inStreptomyces nigrificans by ultraviolet irradiation

Summary Glucose isomerase activity inStreptomyces nigrificans 3014, a producer of antibiotics of the chromomycin group., increased by 198 % as a result of a two-step improvement procedure including the selection of more active variants among antibiotic-producing isolates from population treated with ultraviolet light.     

Natural killer cell activity in cœliac disease: Effect ofin vitro treatment on effector lymphocytes and/or target lymphoblastoid,myeloid and epithelial cell lines with gliadin

To analyze the possible involvement of natural killer (NK) cell activity in the pathogenetic mechanism of cœliac disease (CD) we measured the spontaneous cytotoxic cell activity of peripheral blood mononuclear cells (PMNC) from patients with CD and from healthy donors. No significant differences were found between the NK cell activity of PMNC from healthy donors and from patients with CD using a standard⁵¹Cr release assay. However, a 30-min treatment of PMNC with gliadin inhibited NK cell activity in patients with CD. On the other hand, a 1-d incubation with gliadin induced cytotoxic cell activity of PMNC against the NK-resistant target cells such as the epithelial HT-29 and the lymphoblastoid RAJI cell lines, suggesting that activation of PMNC by cultivation with gliadin can occur.