Chloroplastic glutamine synthetase from Brassica napus.

Detection of a Single Gene Encoding Glutamine Synthetase in Sinapis alba (L.)

Summary Ion-exchange chromatography of glutamine synthetase polypeptides (GS; EC 6.3.1.2) from green leaves and the roots of Sinapis alba yielded identical elution patterns. This is likewise true for GS from etiolated cotyledons. As we have previously demonstrated the identity of GS-enzymes from etiolated and green leaf tissues, the obviously very similar charge properties of GS-proteins indicate the eventual existence of only one type of GS in all mustard plant organs. To further prove this possibility, Southern blot analysis of mustard DNA was carried out using hybridization probes specific to different GS-isoforms. Concluding from the relative strength of the hybridization signals, the G…

Glutamine synthetase from roots of Brassica napus. Nucleotide sequence of a cytosolic isoform.

Purification and Characterization of Glutamine Synthetase Isoenzymes from Leaves and Roots of Brassica napus (L.)

Summary The glutamine synthetase enzymes from leaves (GS2) and roots (GSR) of Brassica napus L. have been purified to homogeneity by the application of a three-stage isolation procedure comprising anion-exchange chromatography, adsorption by hydroxylapatite and gel filtration on Sephacryl 5-300 HR. The isoforms of the enzyme show a differential distribution in leaf and root tissues. Elution profiles of hydroxylapatite chromatography showed a distinct behaviour for GS proteins found in leaves and roots. Denaturing SDS-PAGE and Western blot experiments revealed molecular masses of approximately 43.5 and 40.5 kD for GS2 and GSR subunits, respectively. Moreover, kinetic properties determined us…

Glutamine synthetases of green and etiolated leaves ofSinapis alba : Evidence of the identity of the respective enzyme proteins.

Studies on the glutamine synthetases (GS, EC 6.3.1.2) of green (GS2) and etiolated leaves (GSet) ofSinapis alba L. (cv. Steinacher) revealed striking similarities between the respective enzyme proteins. The enzymes showed corresponding chromatographic properties, both on dimethylaminoethyl-Sephacel and on hydroxylapatite columns. The purified GS proteins were also identical with regard to the molecular weight of their subunits. Isoelectrofocusing of pure GSet yielded two distinct polypeptide bands in the pH 5.6 region of the gels. This pattern corresponded to the two strong bands of GS2. Two charge variants of GS polypeptides could be detected by Western-blot analysis of the soluble protein…