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Curr Opin Struct Biol. 2008 Dec;18(6):673-81. doi: 10.1016/ Epub 2008 Nov 27.

Arginine and nitrogen storage.

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Instituto de Biomedicina de Valencia-Consejo Superior de Investigaciones Cientificas (IBV-CSIC) and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Jaime Roig 11, Valencia 46010, Spain.


When nitrogen is abundant, prokaryotic and eukaryotic oxygen-producing photosynthetic organisms store nitrogen as arginine, by relieving feedback inhibition of the arginine biosynthesis controlling enzyme, N-acetylglutamate kinase (NAGK). The signalling protein PII, an ancient and widely distributed nitrogen/carbon/ADP/ATP sensor, mediates feedback inhibition relief of NAGK by binding to this enzyme. PII phosphorylation or PII binding of ADP or 2-oxoglutarate prevents PII-NAGK complex formation. Crystal structures of NAGK, cyanobacterial and plant PII and corresponding PII-NAGK complexes have been recently determined. In these complexes, two polar PII trimers sandwich one ring-like NAGK hexamer. Each PII subunit contacts one NAGK subunit, triggering a symmetry-restricted narrowing of the NAGK ring, with concomitant adoption by the arginine sites of a low-affinity conformation.

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