2rd5

From Proteopedia

Revision as of 16:46, 21 February 2008

Structural basis for the regulation of N-acetylglutamate kinase by PII in Arabidopsis thaliana

Overview

PII is a highly conserved regulatory protein found in organisms across the three domains of life. In cyanobacteria and plants, PII relieves the feedback inhibition of the rate-limiting step in arginine biosynthesis catalyzed by N-acetylglutamate kinase (NAGK). To understand the molecular structural basis of enzyme regulation by PII, we have determined a 2.5-A resolution crystal structure of a complex formed between two homotrimers of PII and a single hexamer of NAGK from Arabidopsis thaliana bound to the metabolites N-acetylglutamate, ADP, ATP, and arginine. In PII, the T-loop and Trp(22) at the start of the alpha1-helix, which are both adjacent to the ATP-binding site of PII, contact two beta-strands as well as the ends of two central helices (alphaE and alphaG) in NAGK, the opposing ends of which form major portions of the ATP and N-acetylglutamate substrate-binding sites. The binding of Mg(2+).ATP to PII stabilizes a conformation of the T-loop that favors interactions with both open and closed conformations of NAGK. Interactions between PII and NAGK appear to limit the degree of opening and closing of the active-site cleft in opposition to a domain-separating inhibitory effect exerted by arginine, thus explaining the stimulatory effect of PII on the kinetics of arginine-inhibited NAGK.

About this Structure

2RD5 is a Protein complex structure of sequences from Arabidopsis thaliana with , , , and as ligands. Active as Acetylglutamate kinase, with EC number 2.7.2.8 Full crystallographic information is available from OCA.

Reference

Structural basis for the regulation of N-acetylglutamate kinase by PII in Arabidopsis thaliana., Mizuno Y, Moorhead GB, Ng KK, J Biol Chem. 2007 Dec 7;282(49):35733-40. Epub 2007 Oct 3. PMID:17913711

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