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51.
Stefano Ferrari Vittorio Moret Noris Siliprandi 《Molecular and cellular biochemistry》1990,97(1):9-16
Summary Incubation of rat liver mitochondria in the presence of either [32P] Pi or
32
y
-P] ATP resulted in a phosphorylation of four proteins with Mr 50, 47, 44 and 36 kDa, respectively. The endogenous phosphorylation of these proteins in the presence of [32P] Pi was markedly influenced by the osmolarity of the incubation medium and differentially affected by various effectors of mitochondrial functions, such as Ca2+, oligomycin, FCCP, arsenite and dichloroacetate. In particular, the 36 kDa protein, unlike the other proteins, appears to be phosphorylated also by direct incorporation of [32P], independently of respiratory chain-linked ATP synthesis. The four proteins, located in the mitoplasts, seem to be phosphorylated by diiferent protein kinases, as suggested by the observation that the endogenous phosphorylation of 36 kDa protein resulted selectively increased by addition of exogenous protein kinases, such as casein kinases S and TS. A tentative identification of these phosphorylatable protein is discussed. 相似文献
52.
Summary The biosynthesis of rhodanese was studied in human hepatoma cell lines by immunoblotting and pulselabeling experiments using polyclonal antibodies raised against the bovine liver enzyme. Rhodanese, partially purified from human liver, showed an apparent molecular weight of 33,000 daltons, coincident with that of rhodanese from Hep 3B cells. After pulse labeling of Hep 3B cells both at 37°C and 25°C, rhodanese in the cytosol fraction exhibited the same molecular weight as the enzyme isolated from the particulate fraction containing mitochondria. Moreover, newly synthesized rhodanese from total Hep 3B RNA translation products showed the same electrophoretic mobility as rhodanese from Hep 3B cells. These results suggest that rhodanese, unlike most mitochondrial proteins, is not synthesized as a higher molecular weight precursor. 相似文献
53.
Gordon M. Wahler Dennis E. Coyle Nicholas Sperelakis 《Molecular and cellular biochemistry》1990,93(1):69-76
Platelet-activating factor (PAF) has been implicated as one of the mediators of cardiac anaphylaxis. This phospholipid has been shown to have numerous effects on a variety of tissues, including the heart. Among these effects are alterations in the resting potential and generation of arrhythmias at very low concentrations. This suggests that PAF may modulate the activity of the background, inwardly-rectifying potassium current (IK1). Thus, the effects of PAF on IK1 were examined at the single channel level. Ventricular cells were isolated from adult guinea pig hearts and single channel currents recorded from cell-attached patches. PAF had substantial effects on the single channel currents at sub-nanomolar concentrations (10–11 to 10–10 M). PAF initially caused flickering of the channels, followed by a gradual prolonged depression of channel activity. Since these potassium channels play a major role in determining the resting potential and excitability of the cardiac cell, the effects of PAF on IK1 may play a major role in the deleterious electrophysiological actions of PAF on the heart.Abbreviations IK1
Inwardly-rectifying background potassium current
- Lyso-PAF
Lyso-platelet-activating factor
- PAF
Platelet-activating factor 相似文献
54.
Vicente Corbatón Patricio Fernández-Silva Manuel J. López-Pérez Dr. Julio Montoya 《Neurochemical research》1990,15(7):711-717
We have isolated RNA from sheep brain synaptosomes and mitochondria separated by an aqueous two-phase system composed of dextran and poly(ethylene glycol). RNA was fractionated through oligo(dT)-cellulose columns and analyzed by electrophoresis through agarose slab gels containing methylmercuric hydroxide and stained with ethidium bromide. The electrophoretic patterns of the poly(A)-containing RNA fraction from synaptosomes and mitochondria are very similar although some high molecular weight RNA species, clearly visible in the synaptosomal fraction, are scarcely detected in the mitochondrial preparations. The electrophoretic analysis of a cleaner RNA preparation from digitonin-treated free mitochondria (mitoplasts) showed that all the poly (A)-RNA species of the synaptosomal preparation are also present in mitoplast. These results strongly suggest that all the discrete poly(A)-RNA species identified in brain synaptosomes are of mitochondrial origin. 相似文献
55.
Robert S. Aronstam Michael W. Edwards John W. Daly X. Albuquerque 《Neurochemical research》1988,13(2):171-176
The interactions of eight piperidine derivatives with nicotinic receptor complexes fromTorpedo californica electric organ were studied using [125I]alpha-bungarotoxin ([125I]BGT) as a probe for the acetylcholine binding site and [3H]perhydrohistrionicotoxin ([3H]H12-HTX) as a probe for a site associated with the receptor-gated ion channel.Cis- andtrans-2-methyl-6-n-undecanyl piperidines (MUP), major constituents of fire ant venom, had a high-affinity for [3H]H12-HTX binding sites (Ki=0.08–0.24 M), but had no affect on receptor binding. MUP affinity for [3H]H12-HTX binding sites was approximately doubled in the presence of 1 M carbamylcholine. Introduction of a 2-hydroxyl group to the undecanyl side channel had little effect on activity of the alkaloid. The analog 2,6- (but not 3,5-) dimethylpiperidine was a moderately active inhibitor of [3H]H12-HTX binding (K
i-8.8 M). 2-Methylpiperidine was considerably less active (K
i=600 M), although it was more potent than either 3- or 4-methylpiperidine. The affinities of 2,6-dimethylpiperidine and 2-methylpiperidine for [3H]H12-HTX binding sites were decreased in the presence of 1 M carbamylcholine. Carbamylcholine affinity for the receptor was increased by up to 7 fold in the presence of 10 and 32 M MUP, but was decreased in the presence of 2,6-dimethylpiperidine and 2-methylpiperidine. Thecis- andtrans-isomers of MUP were equipotent in producing each of its effects. In these actions, MUP resembles a variety of other compounds derived from 2,6-disubstituted piperidines, including histrionicotoxins, gephyrotoxins and pumiliotoxins. These studies establish the importance of alkyl substitutions in theortho position of the piperidine ring in conferring ion channel specificity, and the importance of substantial alkyl side chains in conferring the ability of channel blockers to stabilize the nicotinic receptor complex in high affinity, desensitized conformations. 相似文献
56.
Magdalena T. Tosteson Michael P. Caulfield Jay J. Levy Michael Rosenblatt Daniel C. Tosteson 《Bioscience reports》1988,8(2):173-183
We have used the chemically synthesized sequence of pre-pro-parathyroid hormone and several of its analogues to test the notion that the capacity of amphipathic peptides to aggregate in membranes and form ion-permeable channels correlates with their ability to function as signal sequences for secreted proteins. We found that pre-pro-parathyroid hormone (the signal sequence and pro-region of parathyroid hormone (M)), as well as some of its analogues, forms aggregates of monomers which are ion-permeable. The ion-permeable aggregates (2–3 monomers) formed by (M) are voltage-dependent and are more permeable for cations than for anions. The compounds which formed ion channels in bilayers also acted as potential signal sequences. We conclude that the ability of peptides to form ion-permeable pathways in bilayers may be correlated to their ability to function as signal peptides. 相似文献
57.
Paul B. M. Joyce David F. Spencer Linda Bonen Michael W. Gray 《Plant molecular biology》1988,10(3):251-262
We have begun a systematic search for potential tRNA genes in wheat mtDNA, and present here the sequences of regions of the wheat mitochondrial genome that encode genes for tRNAAsp (anticodon GUC), tRNAPro (UGG), tRNATyr (GUA), and two tRNAsSer (UGA and GCU). These genes are all solitary, not immediately adjacent to other tRNA or known protein coding genes. Each of the encoded tRNAs can assume a secondary structure that conforms to the standard cloverleaf model, and that displays none of the structural aberrations peculiar to some of the corresponding mitochondrial tRNAs from other eukaryotes. The wheat mitochondrial tRNA sequences are, on average, substantially more similar to their eubacterial and chloroplast counterparts than to their homologues in fungal and animal mitochondria. However, an analysis of regions 150 nucleotides upstream and 100 nucleotides downstream of the tRNA coding regions has revealed no obvious conserved sequences that resemble the promoter and terminator motifs that regulate the expression of eubacterial and some chloroplast tRNA genes. When restriction digests of wheat mtDNA are probed with 32P-labelled wheat mitochondrial tRNAs, <20 hybridizing bands are detected, whether enzymes with 4 bp or 6 bp recognition sites are used. This suggests that the wheat mitochondrial genome, despite its large size, may carry a relatively small number of tRNA genes. 相似文献
58.
Bradley C. Hyman 《Journal of nematology》1988,20(4):523-531
The mitochondrial genome of animal cells is currently under intense investigation by molecular, evolutionary, and population biologists. This review summarizes the available information on the molecular biology of nematode mitochondrial DNA and explains how the fundamental knowledge obtained from these basic studies may be applied to nematode systematics, evolution, and diagnostics. 相似文献
59.
Maitotoxin-Evoked γ-Aminobutyric Acid Release Is Due Not Only to the Opening of Calcium Channels 总被引:1,自引:1,他引:0
The effects of maitotoxin (MTX) on endogenous amino acid release were tested on highly purified striatal neurons differentiated in primary culture. MTX induced a large and concentration-dependent release of gamma-aminobutyric acid (GABA). This effect was abolished when experiments were performed in the absence of external Ca2+, and restored when Ca2+ ions were added after removing the MTX-containing Ca2+-free solution. MTX-induced amino acid release was not affected by 1 microM nifedipine and only slightly inhibited by 1 mM Co2+. MTX also induced a massive accumulation of 45Ca2+ in the neurons which, in contrast to the MTX-evoked GABA release, was totally blocked in the presence of 1 mM Co2+. Whereas 500 nM tetrodotoxin was without significant effect, MTX-evoked GABA release was dependent on the presence of external Na+ and sensitive to nipecotic acid, a GABA uptake inhibitor. It is concluded that, on striatal neurons, MTX induced Na+ influx only in the presence of external Ca2+. The increase in cytoplasmic Na+ ions then triggers the release of GABA. 相似文献
60.
A field study with barley was conducted in 1984 and 1985 to provide data on uptake rates of N, P, K and Mg and their variation as the growing season progressed. Two varieties were grown: Galt in 1984 and Otal in 1985. Soil fertility was maintained at or near optimum conditions. Samples were obtained approximately every 10 days for shoot dry weight, nutrient content and root length measurements. The approximate method (Williams, 1948) traditionally used for calculating uptake rates was found to be invalid for most of the nutrients studied. The method used for measuring uptake rates was the functional approach proposed by Hunt (1973). Inflow,i.e. uptake rate per unit root length, of plant nutrients, decreased with time. However, maximum uptake rates measured in kg ha–1d–1 occurred at about 50 days from sowing because of increasing root length density with time. Inflow or uptake rates were low in 1985 because of moisture deficiency, and grain yield (0.89 t ha–1) was severely depressed. This study demonstrated that Hunt's method is superior and more advantageous than the traditional, approximate method. 相似文献