PubMed · 6786341
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
M W Adams, L E Mortenson, J S Chen. 1980. Hydrogenase.. https://doi.org/10.1016/0304-4173(80)90007-5
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The mechanism by which nitric-oxide (NO) production increases during hypoxia is unknown. To explore the effect of hypoxia upon endothelial nitric-oxide synthase (ecNOS) activity and expression, we exposed bovine aortic endothelial cells (BAEC) to hypoxia (1% O2) for 0-24 h and measured levels of ecNOS mRNA, protein, and activity. The amount of ecNOS mRNA increases to more than twice the basal level after 6 h of hypoxia. Incubation of BAEC with actinomycin D during hypoxia prevents this increase, demonstrating that higher levels of mRNA observed during hypoxia are due to increased synthesis, not to increased stability of ecNOS mRNA. Levels of ecNOS protein increase throughout 24 h of hypoxia to more than twice normoxic levels. Although ecNOS expression increases within 2 h of hypoxia, total activity remains unchanged. To explore the transcriptional regulation of ecNOS, we constructed a reporter plasmid containing the ecNOS promoter region upstream of the luc gene and transfected this reporter plasmid into BAEC. In this system, hypoxia induces a linear increase over time in the expression of luciferase driven by the ecNOS promoter. It is concluded that hypoxia induces an increase in transcription of ecNOS in endothelial cells, activating the regulatory region of ecNOS by undefined transcription factors.
The decomposition of S-nitrosoglutathione (GSNO) in the presence of Cu2+ and glutathione (GSH) was studied by stopped-flow/rapid-scan spectroscopy. Reduction of Cu2+ by GSH and subsequent formation of a GS-*Cu+ complex occurred within 200 ms, with the amount of complex formed depending on the GSH-to-Cu2+ ratio. The rate of GSNO decomposition at a fixed concentration of Cu2+ increased linearly with the concentration of GSH at low GSH-to-Cu2+ ratios (< or = 0.2), but sharply declined at higher ratios. The same pattern was observed for the rate of NO. release, measured with an NO.-sensitive electrode. GSNO decomposition and NO. release in the presence of GSH and/or Cu2+ were completely inhibited by the Cu+ chelator neocuproine, but unaffected by the Cu2+ chelator cuprizone. Ascorbate and cysteine, which will reduce Cu2+ but have little or no affinity for Cu+, also stimulated GSNO decomposition in the presence of Cu2+, but did not inhibit it at higher concentrations. It is concluded that the homolytic cleavage of GSNO is efficiently catalyzed by Cu+ and that the GS-*Cu+ complex is catalytically inactive. By determining the anaerobic GSNO decomposition rates in the presence of varying concentrations of Cu+ a value of 4 x 10(3)M(-1) x s(-1) was derived for the apparent Cu+-GSNO association rate constant.
The FNR protein of Escherichia coli is a redox-responsive transcription regulator that activates and represses a family of genes required for anaerobic and aerobic metabolism. Reconstitution of wild-type FNR by anaerobic treatment with ferrous ions, cysteine and the NifS protein of Azotobacter vinelandii leads to the incorporation of two [4Fe-4S]2+ clusters per FNR dimer. The UV-visible spectrum of reconstituted FNR has a broad absorbance at 420 nm. The clusters are EPR silent under anaerobic conditions but are degraded to [3Fe-4S]+ by limited oxidation with air, and completely lost on prolonged air exposure. The association of FNR with the iron-sulphur clusters is confirmed by CD spectroscopy. Incorporation of the [4Fe-4S]2+ clusters increases site-specific DNA binding about 7-fold compared with apo-FNR. Anaerobic transcription activation and repression in vitro likewise depends on the presence of the iron-sulphur cluster, and its inactivation under aerobic conditions provides a demonstration in vitro of the FNR-mediated aerobic-anaerobic transcriptional switch.