The Crystal Structure of N-Acetyl-L-glutamate Synthase from Neisseria gonorrhoeae Provides Insights into Mechanisms of Catalysis and Regulation

• Published in: The Journal of biological chemistry Vol. 283; no. 11; pp. 7176 - 7184
• Main Authors: Shi, Dashuang, Sagar, Vatsala, Jin, Zhongmin, Yu, Xiaolin, Caldovic, Ljubica, Morizono, Hiroki, Allewell, Norma M., Tuchman, Mendel
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 14-03-2008; American Society for Biochemistry and Molecular Biology
• Subjects: 08 HYDROGEN; Acetyltransferases - chemistry; Allosteric Site; AMINO ACIDS; Amino-Acid N-Acetyltransferase - chemistry; ARGININE; Arginine - chemistry; ATOMS; CATALYSIS; CRYSTAL STRUCTURE; Crystallography, X-Ray; Cysteine - chemistry; DIMERS; ENZYMES; FUNCTIONS; HEIGHT; HYDROGEN; INTERACTIONS; Leucine - chemistry; MATERIALS SCIENCE; Models, Biological; Molecular Conformation; MONOMERS; Neisseria gonorrhoeae; Neisseria gonorrhoeae - enzymology; NITROGEN; PHOSPHOTRANSFERASES; Protein Binding; Protein Structure, Tertiary; PROTEINS; REGULATIONS; RESIDUES; RESOLUTION; RINGS; Serine - chemistry; Stereoisomerism; SYMMETRY
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M707678200

The crystal structures of N-acetylglutamate synthase (NAGS) in the arginine biosynthetic pathway of Neisseria gonorrhoeae complexed with acetyl-CoA and with CoA plus N-acetylglutamate have been determined at 2.5- and 2.6-Å resolution, respectively. The monomer consists of two separately folded domains, an amino acid kinase (AAK) domain and an N-acetyltransferase (NAT) domain connected through a 10-Å linker. The monomers assemble into a hexameric ring that consists of a trimer of dimers with 32-point symmetry, inner and outer ring diameters of 20 and 100Å, respectively, and a height of 110Å. Each AAK domain interacts with the cognate domains of two adjacent monomers across two 2-fold symmetry axes and with the NAT domain from a second monomer of the adjacent dimer in the ring. The catalytic sites are located within the NAT domains. Three active site residues, Arg316, Arg425, and Ser427, anchor N-acetylglutamate in a position at the active site to form hydrogen bond interactions to the main chain nitrogen atoms of Cys356 and Leu314, and hydrophobic interactions to the side chains of Leu313 and Leu314. The mode of binding of acetyl-CoA and CoA is similar to other NAT family proteins. The AAK domain, although catalytically inactive, appears to bind arginine. This is the first reported crystal structure of any NAGS, and it provides insights into the catalytic function and arginine regulation of NAGS enzymes.