| Popis: |
SUMMARYThe enzyme glutamine synthetase (EC 6.3.1.2) is mainly responsible for the incorporation of inorganic nitrogen into organic molecules in plants. In the present work, a new pineGS1(PpGS1b.2) gene was identified, showing a high sequence identity with theGS1b.1gene previously characterized in conifers. Phylogenetic analysis revealed that the presence ofPpGS1b.2is restricted to the generaPinusandPiceaand is not found in other conifers. Gene expression data suggest a putative role ofPpGS1b.2in plant development, similar to otherGS1bgenes from angiosperms, suggesting evolutionary convergence. The characterization of GS1b.1 and GS1b.2 at the structural, physicochemical, and kinetic levels has shown differences even though they have high sequence homology. Alterations in the kinetic characteristics produced by the site-directed mutagenesis approach carried out in this work strongly suggest an implication of amino acids at positions 264 and 267 in the active center of pine GS1b.1 and GS1b.2. Therefore, the amino acid differences between GS1b.1 and GS1b.2 would support the functioning of both enzymes to meet distinct plant needs. |
