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Evidence of covalent modification of glutamine synthetase in the purple sulfur bacterium Thiocapsa roseopersicina

Ruslan N. Ivanovsky , Emir-Asan A. Khatipov
DOI: http://dx.doi.org/10.1111/j.1574-6968.1994.tb07153.x 115-119 First published online: 1 September 1994


It was shown that glutamine synthetase of purple sulfur bacterium Thiocapsa roseopersicina is regulated by covalent modification. This conclusion is made on the basis of results showing that: (i) incubation of cells under conditions of nitrogen deprivation in the light lead to an increase of glutamine synthetase activity; (ii) addition of ammonium to nitrogen-starved cell suspensions caused a rapid decrease of glutamine synthetase activity; (iii) inhibition of glutamine synthetase by feedback modifiers was higher in ammonium-treated cells than in those starved for a nitrogen source; (iv) treatment of purified glutamine synthetase and cell-free extracts with phosphodiesterase was accompanied by an increase of glutamine synthetase activity, indicating the cleavage of modifying residues covalently bound to glutamine synthetase molecules.

Key words
  • Glutamine synthetase
  • Adenylylation
  • Purple sulfur bacteria
  • Thiocapsa roseopersicina

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