Intermembrane electron transport in the absence of added water-soluble carriers.

Electron transport from untreated to mersalyzed microsomal vesicles at the level of NADH-cytochrome b5 reductase or cytochrome b5 has been demonstrated in the absence of added water-soluble electron carriers. A similar effect was shown in the systems "intact mitochondria - mersalyzed microsomes" and "mersalyzed mtiochondria - untreated microsomes". No measurable electron transport between intact and mersalyzed particles of inner mitochondrial membrane was found. The obtained data suggest that the capability to carry out intermembrane electron transfer is specific for NADH-cytochrome b5 reductase and/or cytochrome b5, localized in microsomal and outer mitochondrial membranes.     

Intermembrane transport and antioxidant action of alpha-tocopherol in liposomes

Studies were made of the ability of alpha-tocopherol, incorporated into unilamellar liposomes from saturated or unsaturated phospholipids (donor liposomes) to inhibit the accumulation of lipid peroxidation (LPO) products in unilamellar liposomes from rat cerebral cortex lipids (acceptor liposomes) in the presence of LPO inducer (Fe + ascorbate). With the molar alpha-tocopherol: phospholipids rations from 1:1000 to 1:100 in donor liposomes, obtained through sonication of lipid dispersions, alpha-tocopherol was incorporated into both monolayers of liposomes and was distributed in monomeric form without forming clusters. Based on the dependencies of LPO inhibition on the alpha-tocopherol concentrations, we chose the ones that completely prevented the accumulation of LPO products in donor liposomes. Under these conditions LPO inhibition in mixtures of donor and acceptors liposomes was fully determined by the antioxidant effect of alpha-tocopherol in acceptor liposomes due to its intermembrane transfer. The efficiency of the "intermembrane" antioxidant action of alpha-tocopherol increased in the course of preincubation of donor and acceptor liposomes (up to 60 min) and this increase was more pronounced when the donor liposomes contained unsaturated phospholipids. Evidence was obtained that the intermembrane transfer of alpha-tocopherol did not result from the fusion of donor and acceptor liposomes during preincubation.     

Protein carriers of the electron transport chain of non-photosynthesizing mutants of Chlamydomonas reinhardii]

The amounts of ferredoxin, plastocyanin, ferredoxin-NADP-reductase were determined by electrophoresis and differential spectroscopy. The cytochrome levels in the chloroplasts of non-photosynthesizing mutants Chlamydomonas reinhardii were determined both in active and inactive photosystems. It was shown that the loss of PS-1 activity did not affect the amount and activity of the electron carriers. The disturbances of the donor side of PS-2 in the mutants were accompanied by a loss of the reaction center activity and by a decrease of cytochrome b599. The amounts of other protein components in the mutants with inactive PS-2 remained unchanged. The disturbances in the cytochrome c553 content presumably blocked the electron transfer between the photosystems but did not affect the activity of the reaction centers of PS and the levels of other carriers of the chloroplast electron transport chain.     

Modulation of photosynthetic electron transport in the absence of terminal electron acceptors: characterization of the rbcL deletion mutant of tobacco

Tobacco rbcL deletion mutant, which lacks the key enzyme Rubisco for photosynthetic carbon assimilation, was characterized with respect to thylakoid functional properties and protein composition. The Delta rbcL plants showed an enhanced capacity for dissipation of light energy by non-photochemical quenching which was accompanied by low photochemical quenching and low overall photosynthetic electron transport rate. Flash-induced fluorescence relaxation and thermoluminescence measurements revealed a slow electron transfer and decreased redox gap between Q(A) and Q(B), whereas the donor side function of the Photosystem II (PSII) complex was not affected. The 77 K fluorescence emission spectrum of Delta rbcL plant thylakoids implied a presence of free light harvesting complexes. Mutant plants also had a low amount of photooxidisible P700 and an increased ratio of PSII to Photosystem I (PSI). On the other hand, an elevated level of plastid terminal oxidase and the lack of F0 'dark rise' in fluorescence measurements suggest an enhanced plastid terminal oxidase-mediated electron flow to O2 in Delta rbcL thylakoids. Modified electron transfer routes together with flexible dissipation of excitation energy through PSII probably have a crucial role in protection of PSI from irreversible protein damage in the Delta rbcL mutant under growth conditions. This protective capacity was rapidly exceeded in Delta rbcL mutant when the light level was elevated resulting in severe degradation of PSI complexes.     

Survival of Gd- allele carriers in the absence of malaria

Viability of children in families in which one or both parents had glucose-6-phosphate dehydrogenase deficiency was studied. 159 couples from three districts of the Shekin region of the Azerbaijan SSR were examined. The data were obtained by the half-quality method of fluorescent spots. Four types of marriages were defined using the results of the screening programme. The number of pregnancies and their outcome were analyzed. Elimination of pregnancies in marriages where one or both parents were carriers for Gd- allele, was reliably increased in the antenatal period. This was established under conditions of the absence of selection for hetero- and hemizygotes for this allele in the districts examined. The highest value of elimination of pregnancies was noted in marriages in which both parents were Gd- allele carriers.     

Modulation of photosynthetic electron transport in the absence of terminal electron acceptors: Characterization of the rbcL deletion mutant of tobacco

Tobacco rbcL deletion mutant, which lacks the key enzyme Rubisco for photosynthetic carbon assimilation, was characterized with respect to thylakoid functional properties and protein composition. The ΔrbcL plants showed an enhanced capacity for dissipation of light energy by non-photochemical quenching which was accompanied by low photochemical quenching and low overall photosynthetic electron transport rate. Flash-induced fluorescence relaxation and thermoluminescence measurements revealed a slow electron transfer and decreased redox gap between Q_A and Q_B, whereas the donor side function of the Photosystem II (PSII) complex was not affected. The 77 K fluorescence emission spectrum of ΔrbcL plant thylakoids implied a presence of free light harvesting complexes. Mutant plants also had a low amount of photooxidisible P700 and an increased ratio of PSII to Photosystem I (PSI). On the other hand, an elevated level of plastid terminal oxidase and the lack of F₀ ‘dark rise’ in fluorescence measurements suggest an enhanced plastid terminal oxidase-mediated electron flow to O₂ in ΔrbcL thylakoids. Modified electron transfer routes together with flexible dissipation of excitation energy through PSII probably have a crucial role in protection of PSI from irreversible protein damage in the ΔrbcL mutant under growth conditions. This protective capacity was rapidly exceeded in ΔrbcL mutant when the light level was elevated resulting in severe degradation of PSI complexes.     

Calcium stimualtion of protein kinase C in the absence of added phospholipids

The activity of protein kinase C as isolated and described by Inoue, M., Kishimoto, A., Takai, Y., and Nishizuka, Y. (1977) J. Biol. Chem. $\text{252}$, 7610–7616, can be markedly stimulated by Ca²⁺ in the presence of 4 mM Mg²⁺. This Ca²⁺ dependency does not require the presence of phospholipids or exogenous calmodulin. The increase in activity in the presence of Ca²⁺ is blocked by fluphenazine in the presence of 30 mM 2-mercaptoethanol. These results suggest that a calmodulin-like moiety may be a subunit of prokinase C.     

Morphogenesis of post-Golgi transport carriers

The trans-Golgi network (TGN) is one of the main, if not the main, sorting stations in the process of intracellular protein trafficking. It is therefore of central importance to understand how the key players in the TGN-based sorting and delivery process, the post-Golgi carriers (PGCs), form and function. Over the last few years, modern morphological approaches have generated new insights into the questions of PGC biogenesis, structure and dynamics. Here, we present a view by which the “lifecycle” of a PGC consists of several distinct stages: the formation of TGN tubular export domains (where different cargoes are segregated from each other and from the Golgi enzymes); the docking of these tubular domains onto molecular motors and their extrusion towards the cell periphery along microtubules; the fission of the forming PGC from the donor membrane; and the delivery of the newly formed PGC to its specific acceptor organelle. It is now important to add the many molecular machineries that have been described as operating at the TGN to this “morphofunctional map” of the TGN export process.     

Cross-linked protein complex exhibiting asymmetric oxidation activities in the absence of added cofactor

A protein complex (PC) suspension exhibits asymmetric biooxidation activities in the absence of any added cofactor such as NAD(P)⁺ or FAD. It can be extracted from pea protein (PP)‐gel (PP encapsulated with Ca²⁺ alginate gel and aerated in air for several hours) using hot water by rotary shaking and powdered by the following three steps: (1) forming precipitates from the suspension using 30% (w/v) aqueous (NH₄)₂SO₄, (2) crosslinking the precipitates with 0.25% (v/v) GA, and (3) preparing the cross‐linked powder by freeze‐drying. The cross‐linked PC (CLPC) performed asymmetric oxidation of the toward (R)‐isomers of rac‐ 1 and rac ‐2 in 50 mM glycine–NaOH (pH 9.0) buffer/DMSO cosolvent [2.07% (v/v)] with high enantioselectivity; thus, the (S)‐isomers can be obtained in greater than 99% ee from the corresponding rac‐p‐substituted naphthyl methyl carbinol (rac‐ 1 and rac ‐2 ). The CLPC activity was not only competitively inhibited by addition of either 1.0 mM ZnCl₂ or a chelating agent such as 1.0 mM EDTA but also denatured by pretreatments: autoclaving at 121°C (20 min) or using 6.0 M guanidine–HCl containing 50 mM DTT. These results indicated that the PC catalytic process may utilize an electron transfer system incorporating a redox cation (e.g., Fe²⁺ ? Fe³⁺ or Zn). Therefore, the newly introduced CLPC can asymmetrically oxidize the substrates without the addition of any cofactor resulting in a low‐cost organic method. Overall, our results show that the CLPC is an easily prepared, low‐cost reagent that can function under mild conditions and afford stereoselectivity, regioselectivity, and substrate specificity. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 953–961, 2012     

Periplasmic electron carriers and photo-induced electron transfer in the photosynthetic bacterium Ectothiorhodospira sp.

A detailed analysis of the periplasmic electron carriers of the photosynthetic bacterium Ectothiorhodospira sp. has been performed. Two low mid-point redox potential electron carriers, cytochrome c′ and cytochrome c, are detected. A high potential iron–sulfur protein is the only high mid-point redox potential electron transfer component present in the periplasm. Analysis of light-induced absorption changes shows that this high potential iron–sulfur protein acts in vivo as efficient electron donor to the photo-oxidized high potential heme of the Ectothiorhodospira sp. reaction center. This revised version was published online in June 2006 with corrections to the Cover Date.