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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

Abstract

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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