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21.
S Abe S Araki M Satake N Fujiwara K Kon S Ando 《The Journal of biological chemistry》1991,266(15):9939-9943
A phosphonoglycosphingolipid, named F-21, was found in the nervous system of Aplysia kurodai by two-dimensional thin-layer chromatography (Abe, S., Araki, S., and Satake, M. (1986) Biomed. Res. (Tokyo) 7, 47-51). F-21 was isolated from the nervous tissue of Aplysia in this study, and its chemical structure was characterized as follows, where 2-AEP is 2-aminoethylphosphonate. (Formula; see text) The major aliphatic components of the ceramide portion were palmitic acid (75%), stearic acid (22%), octadeca-4-sphingenine (43%), and anteisononadeca-4-sphingenine (54%). Some information on the steric interactions in the sugar moiety was obtained by NMR spectroscopy. The ring protons of the internal galactose, H1, H3, and H4 and the H3 of the side chain galactose were shifted, as compared to the corresponding protons of dephosphonylated F-21. This may indicate the interactions between the 2-AEP residue of N-acetylgalactosamine and the internal galactose and between the N-acetyl group of N-acetylgalactosamine and the side chain galactose, implying a sterically restricted and unique structure that may relate to some biological functions of F-21. 相似文献
22.
T Araki J Funatsu M Kuramoto H Konno T Torikata 《The Journal of biological chemistry》1992,267(28):19944-19947
The complete amino acid sequence of acidic chitinase from yam (Dioscorea japonica) aerial tubers was determined. The protein is composed of a single polypeptide chain of 250 amino acid residues and has a calculated molecular mass of 27,890 Da. There is an NH2-terminal domain, a hinge region, and a main structure, typical for class I chitinases (Shinshi, H., Neuhaus, J.-M., Ryals, J., and Meins, F., Jr. (1990) Plant Mol. Biol. 14, 357-368). We have obtained the first evidence for an acidic class I chitinase. Comparison with sequences of other class I chitinases revealed approximately 40% sequence similarity, a value lower than that for other class I chitinases (70-80%). We assume that there is a local conformational change in the molecule; cysteine residues that probably form disulfide bonds are completely conserved, with the exception of Cys-178. The difference in structure between this chitinase and other basic class I chitinases suggests that acidic and basic isoforms should be grouped into subclasses; this protein is an ethylene- or a pathogen-independent chitinase produced by a gene that is inherent in the tuber. 相似文献
23.
T Araki 《Journal of general microbiology》1992,138(10):2075-2082
In the psychrophilic bacterium Vibrio sp. strain ANT-300, the rate of protein degradation in vivo, measured at fixed temperatures, increased with elevation of the growth temperature. A shift in growth temperature induced a marked increase in this rate. Dialysed cell-free extracts hydrolysed exogenous insulin, globin and casein (in decreasing order of activity) but did not hydrolyse exogenous cytochrome c. Cells contained at least seven protease separated by DEAE-Sephacel chromatography, one of which was an ATP-dependent serine protease. The ATP-dependent proteolytic activity in extracts of cells incubated for 3 h at 16 degrees C after a shift-up from 0 degrees C increased to a level 36% and 17% higher than that of cells grown at 0 degrees C and 13 degrees C, respectively. A shift-down to 0 degrees C from 13 degrees C induced only a slight increase in the proteolytic activity. Extracts of all cells, whether exposed to temperature shifts or not, showed the same temperature dependence with respect to both ATP-dependent and ATP-independent protease activity. In all the extracts these proteases also exhibited the same heat lability. The ATP-dependent protease was inactivated by incubation at temperatures above 25 degrees C. There was an increase in ATP-independent protease activity during incubation at temperatures between 25 and 30 degrees C, but a decrease at 35 degrees C and higher. These results suggest that the marked increases in proteolysis in vivo, caused by a shift in temperature, may result not only from increases in levels of ATP-dependent serine protease(s) but also from increases in the susceptibility of proteins to degradation. 相似文献
24.
25.
Takako Sakai Jun Imamura 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,84(7-8):923-929
Summary We have investigated the fate of the mitochondrial genomes of cybrids derived from donor-recipient protoplast fusion between X-irradiated Raphanus sativus (cms line) and iodoacetamide-treated Brassica napus cv. Westar. Two out of ten fusion products were male-sterile with the diploid chromosome number of B. napus. The mitochondrial (mt) genomes of the cybrids and their progeny were further analyzed by DNA-DNA hybridizaion using the pea mitochondrial ATPase subunit gene (atpA) as a probe. One cybrid, 18-3, had a 3.0 kb fragment characteristic of B. napus and a 2.0 kb non-parental fragment when the BamHI-digested DNA was hybridized with the probe. In the first-backcrossed progeny of this cybrid, the hybridization pattern was not stably inherited. A 4.0 kb radish fragment, not detectable in the cybrid, appeared in one of the BC1 generation siblings, and the 2.0 kb non-parental fragment was lost in another. The hybridization patterns in BC1 progeny siblings of cybrid 12-9 were also varied. The alteration of mtDNA in the cybrid progeny continued to the BC2 generation. There was no clear evidence of a heteroplasmic state or of sub-stoichiometric molecules in the mt genome of cybrid 18-3. A possible cause of the observed alteration in the mt genome is discussed. 相似文献
26.
S Shinozawa Y Gomita Y Araki 《Physiological chemistry and physics and medical NMR》1991,23(2):101-106
The effects of Aclarubicin (aclacinomycin A; ACM) and Doxorubicin (adriamycin; ADM) on oxidative phosphorylation in rat liver mitochondria were studied in vitro. The state 3 oxygen uptake of mitochondria was reduced by only 2% by 20 microM of ADM, while the same concentration of ACM caused a 67% reduction. When 20 microM of ADM acted on state 4a oxygen uptake of mitochondria, only a slight decrease in state 3, state 4b, dinitrophenol-stimulated respiration and the respiratory control index was observed. In contrast 20 microM of ACM caused significant inhibition of all the above factors when compared with the controls. It was concluded that ACM has strong inhibitory action on the mitochondrial electron transfer system in vitro, and that one can expect functional failure of mitochondria to occur clinically during adverse response to the administration of this drug. 相似文献
27.
28.
Shant M. Mahserejian Jared P. Scripture Ava J. Mauro Elizabeth J. Lawrence Erin M. Jonasson Kristopher S. Murray Jun Li Melissa Gardner Mark Alber Marija Zanic Holly V. Goodson 《Molecular biology of the cell》2022,33(3)
Microtubules (MTs) are cytoskeletal fibers that undergo dynamic instability (DI), a remarkable process involving phases of growth and shortening separated by stochastic transitions called catastrophe and rescue. Dissecting DI mechanism(s) requires first characterizing and quantifying these dynamics, a subjective process that often ignores complexity in MT behavior. We present a Statistical Tool for Automated Dynamic Instability Analysis (STADIA) that identifies and quantifies not only growth and shortening, but also a category of intermediate behaviors that we term “stutters.” During stutters, the rate of MT length change tends to be smaller in magnitude than during typical growth or shortening phases. Quantifying stutters and other behaviors with STADIA demonstrates that stutters precede most catastrophes in our in vitro experiments and dimer-scale MT simulations, suggesting that stutters are mechanistically involved in catastrophes. Related to this idea, we show that the anticatastrophe factor CLASP2γ works by promoting the return of stuttering MTs to growth. STADIA enables more comprehensive and data-driven analysis of MT dynamics compared with previous methods. The treatment of stutters as distinct and quantifiable DI behaviors provides new opportunities for analyzing mechanisms of MT dynamics and their regulation by binding proteins. 相似文献
29.
Methylation protects miRNAs and siRNAs from a 3'-end uridylation activity in Arabidopsis 总被引:5,自引:0,他引:5
Small RNAs of 21-25 nucleotides (nt), including small interfering RNAs (siRNAs) and microRNAs (miRNAs), act as guide RNAs to silence target-gene expression in a sequence-specific manner. In addition to a Dicer homolog, DCL1, the biogenesis of miRNAs in Arabidopsis requires another protein, HEN1. miRNAs are reduced in abundance and increased in size in hen1 mutants. We found that HEN1 is a miRNA methyltransferase that adds a methyl group to the 3'-most nucleotide of miRNAs, but the role of miRNA methylation was unknown. Here, we show that siRNAs from sense transgenes, hairpin transgenes, and transposons or repeat sequences, as well as a new class of siRNAs known as trans-acting siRNAs, are also methylated in vivo by HEN1. In addition, we show that the size increase of small RNAs in the hen1-1 mutant is due to the addition of one to five U residues to the 3' ends of the small RNAs. Therefore, a novel uridylation activity targets the 3' ends of unmethylated miRNAs and siRNAs in hen1 mutants. We conclude that 3'-end methylation is a common step in miRNA and siRNA metabolism and likely protects the 3' ends of the small RNAs from the uridylation activity. 相似文献
30.
Inhibition of mitochondrial complex I improves glucose metabolism independently of AMPK activation 下载免费PDF全文
Wo‐Lin Hou Jun Yin Miriayi Alimujiang Xue‐Ying Yu Li‐Gen Ai Yu‐qian Bao Fang Liu Wei‐Ping Jia 《Journal of cellular and molecular medicine》2018,22(2):1316-1328
Accumulating evidences showed metformin and berberine, well‐known glucose‐lowering agents, were able to inhibit mitochondrial electron transport chain at complex I. In this study, we aimed to explore the antihyperglycaemic effect of complex I inhibition. Rotenone, amobarbital and gene silence of NDUFA13 were used to inhibit complex I. Intraperitoneal glucose tolerance test and insulin tolerance test were performed in db/db mice. Lactate release and glucose consumption were measured to investigate glucose metabolism in HepG2 hepatocytes and C2C12 myotubes. Glucose output was measured in primary hepatocytes. Compound C and adenoviruses expressing dominant negative AMP‐activated protein kinase (AMPK) α1/2 were exploited to inactivate AMPK pathway. Cellular NAD+/NADH ratio was assayed to evaluate energy transforming and redox state. Rotenone ameliorated hyperglycaemia and insulin resistance in db/db mice. It induced glucose consumption and glycolysis and reduced hepatic glucose output. Rotenone also activated AMPK. Furthermore, it remained effective with AMPK inactivation. The enhanced glycolysis and repressed gluconeogenesis correlated with a reduction in cellular NAD+/NADH ratio, which resulted from complex I suppression. Amobarbital, another representative complex I inhibitor, stimulated glucose consumption and decreased hepatic glucose output in vitro, too. Similar changes were observed while expression of NDUFA13, a subunit of complex I, was knocked down with gene silencing. These findings reveal mitochondrial complex I emerges as a key drug target for diabetes treatment. Inhibition of complex I improves glucose homoeostasis via non‐AMPK pathway, which may relate to the suppression of the cellular NAD+/NADH ratio. 相似文献