Regulation of nitrogenase levels in Anabaena sp. ATCC 33047 and other filamentous cyanobacteria |
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Authors: | Juan L Ramos Francisco Madueño Miguel G Guerrero |
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Institution: | (1) Departamento de Bioquímica, Facultad de Biología y C.S.I.C., Apartado 1095, E-41080 Sevilla, Spain;(2) Present address: Departement de Biochimie Médicale, Centre Médical Universitaire, 1211 Genève 4, Switzerland |
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Abstract: | Incubation in the dark of photoautotrophically grown N2-fixing heterocystous cyanobacteria leads to a loss of nitrogenase activity. Original levels of nitrogenase activity are rapidly regained upon re-illumination of the filaments, in a process dependent on de novo protein synthesis. Ammonia, acting indirectly through some of its metabolic derivatives, inhibits the light-promoted development of nitrogenase activity in filaments of Anabaena sp. ATCC 33047 and several other cyanobacteria containing mature heterocysts. The ammonia-mediated control system is also operative in N2-fixing filaments in the absence of any added source of combined nitrogen, with the ammonia resulting from N2-fixation already partially inhibiting full expression of nitrogenase. High nitrogenase levels, about two-fold higher than those in normal N2-fixing Anabaena sp. ATCC 33047, are found in cell suspensions which have been treated with the glutamine synthetase inhibitor l-methionine-d,l-sulfoximine or subjected to nitrogen starvation. Filaments treated in either way are insensitive to the ammonia-promoted inhibition of nitrogenase development, although this insensitivity is only transitory for the nitrogen-starved filaments, which become ammonia-sensitive once they regain their normal nitrogen status.Abbreviations Chl
chlorophyll
- EDTA
ethylenediaminetetraacetic acid
- MSX
l-methionine-d,l-sulfoximine |
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Keywords: | Ammonia Anabaena Cyanobacteria Nitrogen fixation Nitrogenase Nostoc |
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