Genes for elongation factor EF-1 alpha in the brine shrimp Artemia |
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Authors: | Nicholas M Shaw Roy W Harding |
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Institution: | Radiation Biology Laboratory, Smithsonian Institution, 12441 Parklawn Drive, Rockville, MD 20852-1773, USA |
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Abstract: | Neurospora crassa had a heat-stable (up to 95 degrees C), soluble cyclic nucleotide phosphodiesterase (PDE). Both unheated and heat-stable PDE activities were inhibited by micromolar concentrations of Ca2+. This inhibition was reversed by EGTA or EDTA in molar excess of the Ca2+ concentration. Calmodulin was not involved in the Ca2+ inhibition, nor was Ca2+ inhibition of the heat-stable PDE due to cleavage inactivation of the enzyme by a Ca2+-stimulated protease. In addition to Ca2+, several other cations inhibited the activity of the heat-stable enzyme. Cyclic AMP and cGMP, but not 2'3' cAMP were substrates for both unheated and heat-stable PDEs. This is the first report of a PDE which is inhibited by micromolar concentrations of Ca2+. |
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Keywords: | Cyclic nucleotide phosphodiesterase Heat stability PMSF phenylmethylsulfonyl fluoride EGTA TLC thin-layer chromatography |
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