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Structural and functional analysis of the PII nitrogen sensor in maritime pine

N-acetyl-L-glutamate kinase (NAGK) is a key enzyme for arginine and polyamine formation in plants, and hence for nitrogen metabolism. PII proteins act as sensors of the N/C status and control NAGK and other target proteins in response to ATP/ADP and 2-oxoglutarate levels. NAGK is inhibited by arginine itself. We investigate here the structure-function relationships of two novel PII proteins from Pinus pinaster (maritime pine), termed PpPIIa and PpPIIb. Three-dimensional modelling, bacterial expression and enzymatic studies were conducted to investigate the regulation and formation of NAGK-PII complexes. The interaction between PpPIIa/PpPIIb and PpNAGK is enhanced by high levels of glutamine and contributes to relieve the feedback inhibition of PpNAGK by arginine. Moreover, the two PII transcripts show different abundance during embryogenesis and germination. The potential roles of both PII proteins are integrated in the regulation of nitrogen metabolism.

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Structural model of a dimer PpPIIa-NAGK. PpPIIa ligands: Mg2+ (green), ATP (red) and glutamine (violet). A molecule of N-acetylglutamate is shown at the active site of NAGK (dark blue).

Original Paper:

Llebrés, M.T., Pascual, M.B., Valle, C., de la Torre, F.N., Valderrama-Martin, J.M., Gómez, L., Avila, C., Cánovas, F.M. 2020. Structural and Functional Characteristics of Two Molecular Variants of the Nitrogen Sensor PII in Maritime Pine. Frontiers in Plant Science 11, 823. DOI: 10.3389/fpls.2020.00823

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