Aging affects expression of 70-kDa heat shock proteins in Drosophila.
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We examined the effect of cellular aging on adult mortality and hsp70 gene expression in Drosophila melanogaster under thermal stress. The results showed that flies exposed to 37 degrees C for various time intervals had reduced survival rate with age. The level of hsp70 mRNA increases in flies up to 23-28 days of age, but then declines as they get older. When flies are shifted to 25 degrees C after 30 min of heat stress, the time-dependent decrease in hsp70 mRNA levels occurs more rapidly in young flies than in old ones. The hsp70 mRNA present during this recovery period is translated into protein, and senescent flies continue to synthesize this protein for up to 5 h after heat shock. The prolonged expression of hsp70 RNA during recovery from heat shock was also observed in young flies fed canavanine, an arginine analogue. These data suggest that in old insects, the accumulation of conformationally altered proteins plays a role in the regulation of hsp70 RNA expression. These results are discussed in relation to the finding that old flies are more sensitive to thermal stress than young ones. (+info)
Quality control of a transcriptional regulator by SUMO-targeted degradation.
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PCNA monoubiquitylation and DNA polymerase eta ubiquitin-binding domain are required to prevent 8-oxoguanine-induced mutagenesis in Saccharomyces cerevisiae.
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L-Arginine kinase from tobacco hornworm, Manduca sexta (L.). Purification, properties, and interaction with L-canavanine.
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Arginine kinase (adenosine 5'-triphosphate: L-arginine phosphotransferase, EC 2.7.3.3) was purified from the larvae of the tobacco hornworm, Manduca sexta (L). This enzyme catalyzes the production of L-phosphoarginine, which is the principal reserve of high energy phosphate compounds in insect muscle. The enzyme also phosphorylates L-canavanine, a guanidinooxy analogue of arginine which severely disrupts all developmental stages of this insect. Evaluations of certain kinetic and thermodynamic parameters of the reactions with arginine and canavanine suggest that reactions known to be much more sensitive to canavanine, such as protein synthesis or genome expression, rather than phosphagen formation and function account for the pronounced toxicity of canavanine in this insect. Sedimentation equilibrium and electrophoresis on polyacrylamide gels containing sodium dodecyl sulfate indicate that this insect enzyme has a molecular weight of about 40,000. This value is consistent with molecular weights of arginine kinases of non-insect arthropods. Its amino acid composition is also very similar to that of other arthropod arginine kinases. Km values for the enzyme are: L-arginine, 0.5 mM; Mg-ATP, 2.5 mM; L-canavanine, 22 mM; L-phosphoarginine, 0.7 mM; Mg-ADP, 0.45 mM; and L-phosphocanavanine, 27 mM. Turnover numbers (expressed as moles of product per min per mol of enzyme) are: L-arginine, 8,320; L-canavanine, 1,635; L-phosphoarginine, 25,875; and L-phosphocanavanine, 3,040. The apparent equilibrium constants at 37 degrees for phosphagen formation are 0.44 with arginine and 0.1 with canavanine. A procedure for L-phosphocanavanine synthesis is also presented. (+info)
Plant insecticide L-canavanine repels Drosophila via the insect orphan GPCR DmX.
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C-terminal flap endonuclease (rad27) mutations: lethal interactions with a DNA ligase I mutation (cdc9-p) and suppression by proliferating cell nuclear antigen (POL30) in Saccharomyces cerevisiae.
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The reciprocal relationship between heme oxygenase and nitric oxide synthase in the organs of lipopolysaccharide-treated rodents.
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The production of nitric oxide (NO) by inducible NO synthase (NOS) and carbon monoxide (CO) by inducible heme oxygenase (HO) contributes greatly to endotoxemia. Reciprocal relationships have been proposed between the NO/NOS and CO/HO systems. However, the interaction between these systems during endotoxemia is unclear, and it is unknown whether the interactive behavior differs among organs. Using endotoxic rats, we studied the effects of the inducible NOS (iNOS) inhibitor L-canavanine (CAN), and the HO inhibitor zinc protoporphyrin (ZPP) on gene expression and protein levels of iNOS, endothelial NOS (eNOS), inducible HO (HO-1), and constitutive HO (HO-2) in the brain, lung, heart, liver and kidney tissue. Intravenous injection of LPS significantly increased iNOS and HO-1 gene expression in all organs. The effects of LPS on eNOS gene expression differed among organs, with increased expression in the liver and kidney, and no change in the lung, brain and heart. ZPP administration down-regulated the LPS-induced increase in HO-1 expression and produced a further increase in iNOS expression in all organs. These data suggest that the CO/HO system modifies the NO/NOS system in endotoxic organs, and that there were only minor organ-specific behaviors in terms of the relationship between these systems in the organs examined. (+info)