PDBsum entry 1j4b

Ligase

PDB id: 1j4b

Contents

Protein chain

432 a.a. *

Waters ×96

* Residue conservation analysis

PDB id:

1j4b

Name:

Ligase

Title:

Recombinant mouse-muscle adenylosuccinate synthetase

Structure:

Adenylosuccinate synthetase. Chain: a. Synonym: adss1. Engineered: yes

Source:

Mus musculus. House mouse. Organism_taxid: 10090. Tissue: muscle. Cellular_location: cytoplasm. Gene: adss1. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Biol. unit:

Dimer (from PDB file)

Resolution:

2.50Å R-factor: 0.207 R-free: 0.272

Authors:

C.V.Iancu,T.Borza,J.Y.Choe,H.J.Fromm,R.B.Honzatko

Key ref:

C.V.Iancu et al. (2001). Recombinant mouse muscle adenylosuccinate synthetase: overexpression, kinetics, and crystal structure. J Biol Chem, 276, 42146-42152. PubMed id: 11560929 DOI: 10.1074/jbc.M106294200

Date:

07-Sep-01 Release date: 21-Nov-01

Protein chain

P28650  (PURA1_MOUSE) -  Adenylosuccinate synthetase isozyme 1 from Mus musculus

Seq: 457 a.a.

Struc: 432 a.a.

Enzyme reactions

• Enzyme class: E.C.6.3.4.4 - adenylosuccinate synthase.
• Pathway: AMP and GMP Biosynthesis
• Reaction: IMP + L-aspartate + GTP = N₆-(1,2-dicarboxyethyl)-AMP + GDP + phosphate + 2 H⁺

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1074/jbc.M106294200

J Biol Chem 276:42146-42152 (2001)

PubMed id: 11560929

Recombinant mouse muscle adenylosuccinate synthetase: overexpression, kinetics, and crystal structure.

C.V.Iancu, T.Borza, J.Y.Choe, H.J.Fromm, R.B.Honzatko.

ABSTRACT

Vertebrates possess two isozymes of adenylosuccinate synthetase. The acidic isozyme is similar to the synthetase from bacteria and plants, being involved in the de novo biosynthesis of AMP, whereas the basic isozyme participates in the purine nucleotide cycle. Reported here is the first instance of overexpression and crystal structure determination of a basic isozyme of adenylosuccinate synthetase. The recombinant mouse muscle enzyme purified to homogeneity in milligram quantities exhibits a specific activity comparable with that of the rat muscle enzyme isolated from tissue and K(m) parameters for GTP, IMP, and l-aspartate (12, 45, and 140 microm, respectively) similar to those of the enzyme from Escherichia coli. The mouse muscle and E. coli enzymes have similar polypeptide folds, differing primarily in the conformation of loops, involved in substrate recognition and stabilization of the transition state. Residues 65-68 of the muscle isozyme adopt a conformation not observed in any previous synthetase structure. In its new conformation, segment 65-68 forms intramolecular hydrogen bonds with residues essential for the recognition of IMP and, in fact, sterically excludes IMP from the active site. Observed differences in ligand recognition among adenylosuccinate synthetases may be due in part to conformational variations in the IMP pocket of the ligand-free enzymes.

Selected figure(s)

Figure 3.
Fig. 3. Subunit interface of mouse muscle adenylosuccinate synthetase. Top panel, overview of the subunits in the dimer as viewed down its molecular 2-fold axis. Bottom panel, a more detailed presentation of side chain interactions. The viewing orientation is the same for the top and bottom panels. This figure was drawn by MOLSCRIPT (47).

Figure 4.
Fig. 4. Stereoview of segment 65-68 of the mouse muscle synthetase. Top panel, residues 65-68 and associated omit electron density contoured at 1 with a cut-off radius of 1 Å. Middle and bottom panels, conformational differences between residues 65-68 of the mouse muscle synthetase (bold lines) and corresponding residues of the ligand-free (middle panel) and ligated (bottom panel) E. coli enzyme. The dashed lines represent donor-acceptor interactions.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2001, 276, 42146-42152) copyright 2001.

Figures were selected by an automated process.