Dissociation by NH4Cl treatment of the enzymic activities of glutamine synthetase II from Rhizobium leguminosarum biovar viceae

Abstract

Glutamine synthetase I1 (GSII) was purified to homogeneity from Rhizobium leguminosarum biovar viceae and characterized.-The Sequence of 26 m i n o acid?esidues from the amino-terminal end bf the protein showed high similarity with the sequence of GSII from Bradyrhizobium japonicum or from Rhizobium meliloti. Non-denaturing PAGE showed that GSII, either in crude extracts or in the pure state, was a mixture of an octamer and a tetramer and that under specific conditions the octamerltetramer ratio could be modified in either direction. The pure enzyme was used to raise an antiserum which was highly specific. Addition of NH4CI to a bacterial culture derepressed for GSII caused a specific decrease in transferase activity, faster than the one observed when the amount of immunoreactive material was measured by different methods. On the other hand, biosynthetic activity, measured as the rate of ADP or glutamine formation, paralleled the rate of decrease in immunoreactive material. A partially purified enzyme preparation retained this dissociation of kinetic parameters, strongly suggesting a post-translational modification. These findings are discussed with respect to the possible role of GSII in the Rhizobium-legume symbiosis.

Molecular Identification and Characterization of Cytosolic Isoforms of Glutamine Synthetase in Maize Roots

“…In this case, the change has been attributed to regulation at both the transcriptional and the post-translational level. In Rhizobium leguminosarum biovar viceae, the addition of ammonia to the culture medium decreases the transferase activity of GSII, a eukaryotic type of GS, by a post-translational manner (41). In this study, we found that GSr was more heat-labile than GS1 (Fig.…”

Genetic and biochemical characterization of the two glutamine synthetases GSI and GSII of the phosphinothricyl-alanyl-alanine producer, Stveptomyces viridochromogenes Tu494

“…No reactivation was observed after SVPDE treatment. This result suggested that GSII is not regulated by adenylylation, but it does not exclude the possibility of another type of post-translational regulation as has been suggested for Rhizobium leguminosarurn GSII (Manco et al, 1992).…”

Key Role of Bacterial NH 4 + Metabolism in Rhizobium-Plant Symbiosis

“…The expression of the glnII gene is activated under N deficiency (for a review, see reference 54) and requires an upstream activating sequence (140). When R. leguminosarum is switched to an NH 4 ϩ -containing medium, glnII transcription is 10-fold repressed, but GSII activity and the GSII protein become undetectable (103,140). That this is due to a posttranscriptional control mechanism of glnII expression has recently been demonstrated (172,183).…”

“…Regulation of GSI concentration and activity (adenylylation) is similar in other rhizobial species (for a review, see reference 116). GSII, encoded by the glnII gene, is a heat-sensitive (relative to GSI) octameric enzyme (103). The expression of the glnII gene is activated under N deficiency (for a review, see reference 54) and requires an upstream activating sequence (140).…”