A Medicago truncatula Homoglutathione Synthetase Is Derived from Glutathione Synthetase by Gene Duplication1 (original) (raw)

The structures of cytosolic and plastid-located glutamine synthetases from Medicago truncatula reveal a common and dynamic architecture

Acta Crystallographica Section D Biological Crystallography, 2014

The first step of nitrogen assimilation in higher plants, the energy-driven incorporation of ammonia into glutamate, is catalyzed by glutamine synthetase. This central process yields the readily metabolizable glutamine, which in turn is at the basis of all subsequent biosynthesis of nitrogenous compounds. The essential role performed by glutamine synthetase makes it a prime target for herbicidal compounds, but also a suitable intervention point for the improvement of crop yields. Although the majority of crop plants are dicotyledonous, little is known about the structural organization of glutamine synthetase in these organisms and about the functional differences between the different isoforms. Here, the structural characterization of two glutamine synthetase isoforms from the model legumeMedicago truncatulais reported: the crystallographic structure of cytoplasmic GSII-1a and an electron cryomicroscopy reconstruction of plastid-located GSII-2a. Together, these structural models unv...