2V5H

Controlling the storage of nitrogen as arginine: the complex of PII and acetylglutamate kinase from Synechococcus elongatus PCC 7942

Summary for 2V5H

• Entry DOI: 10.2210/pdb2v5h/pdb
• Related: 1QY7 2JJ4
• Descriptor: ACETYLGLUTAMATE KINASE, NITROGEN REGULATORY PROTEIN P-II, N-ACETYL-L-GLUTAMATE, ... (7 entities in total)
• Functional Keywords: amino-acid biosynthesis, transcription regulation, transferase, cyanobacteria, transcription, n-acetyl-l-glutamate kinase, pii signal protein, nucleotide-binding, acetylglutamate, phosphorylation, amino acid kinase, glnb, kinase, trimer, hexamer, atp-binding, arginine inhibition, arginine biosynthesis
• Biological source: SYNECHOCOCCUS ELONGATUS; More
• Cellular location: Cytoplasm : Q6V1L5
• Total number of polymer chains: 12
• Total formula weight: 282988.18

Authors

Llacer, J.L.,Marco-Marin, C.,Gil-Ortiz, F.,Fita, I.,Rubio, V. (deposition date: 2007-07-04, release date: 2007-10-16, Last modification date: 2023-12-13)

Primary citation

Llacer, J.L.,Contreras, A.,Forchhammer, K.,Marco-Marin, C.,Gil-Ortiz, F.,Maldonado, R.,Fita, I.,Rubio, V.
The Crystal Structure of the Complex of Pii and Acetylglutamate Kinase Reveals How Pii Controls the Storage of Nitrogen as Arginine.
Proc.Natl.Acad.Sci.USA, 104:17644-, 2007

PubMed Abstract: Photosynthetic organisms can store nitrogen by synthesizing arginine, and, therefore, feedback inhibition of arginine synthesis must be relieved in these organisms when nitrogen is abundant. This relief is accomplished by the binding of the PII signal transduction protein to acetylglutamate kinase (NAGK), the controlling enzyme of arginine synthesis. Here, we describe the crystal structure of the complex between NAGK and PII of Synechococcus elongatus, at 2.75-A resolution. We prove the physiological relevance of the observed interactions by site-directed mutagenesis and functional studies. The complex consists of two polar PII trimers sandwiching one ring-like hexameric NAGK (a trimer of dimers) with the threefold axes of these molecules aligned. The binding of PII favors a narrow ring conformation of the NAGK hexamer that is associated with arginine sites having low affinity for this inhibitor. Each PII subunit contacts one NAGK subunit only. The contacts map in the inner circumference of the NAGK ring and involve two surfaces of the PII subunit. One surface is on the PII body and interacts with the C-domain of the NAGK subunit, helping widen the arginine site found on the other side of this domain. The other surface is at the distal region of a protruding large loop (T-loop) that presents a novel compact shape. This loop is inserted in the interdomain crevice of the NAGK subunit, contacting mainly the N-domain, and playing key roles in anchoring PII on NAGK, in activating NAGK, and in complex formation regulation by MgATP, ADP, 2-oxoglutarate, and by phosphorylation of serine-49.

PubMed: 17959776
DOI: 10.1073/PNAS.0705987104

Experimental method

X-RAY DIFFRACTION (2.75 Å)