PDBsum entry 1ajs

Aminotransferase

PDB id: 1ajs

Contents

Protein chains

412 a.a. *

Ligands

PLA

Waters ×331

* Residue conservation analysis

PDB id:

1ajs

Name:

Aminotransferase

Title:

Refinement and comparison of the crystal structures of pig cytosolic aspartate aminotransferase and its complex with 2-methylaspartate

Structure:

Aspartate aminotransferase. Chain: a. Other_details: the coenzyme pyridoxal 5'-phosphate in subunit a forms a schiff base with the substrate analog 2-methylaspartate, and forms the external aldimine. But due to crystal lattice packings the coenzyme in subunit b is still in the internal aldimine with the side chain of lys 258.. Aspartate aminotransferase. Chain: b.

Source:

Sus scrofa. Pig. Organism_taxid: 9823. Organism_taxid: 9823

Biol. unit:

Dimer (from PDB file)

Resolution:

1.60Å R-factor: 0.173

Authors:

S.Rhee,M.M.Silva,C.C.Hyde,P.H.Rogers,C.M.Metzler,D.E.Metzler,A.Arnone

Key ref:

S.Rhee et al. (1997). Refinement and comparisons of the crystal structures of pig cytosolic aspartate aminotransferase and its complex with 2-methylaspartate. J Biol Chem, 272, 17293-17302. PubMed id: 9211866 DOI: 10.1074/jbc.272.28.17293

Date:

08-May-97 Release date: 20-Aug-97

Protein chains

P00503  (AATC_PIG) -  Aspartate aminotransferase, cytoplasmic from Sus scrofa

Seq: 413 a.a.

Struc: 412 a.a.*

* PDB and UniProt seqs differ at 3 residue positions (black crosses)

Enzyme reactions

• Enzyme class 1: E.C.2.6.1.1 - aspartate transaminase.
• Reaction: L-aspartate + 2-oxoglutarate = oxaloacetate + L-glutamate
• Cofactor: Pyridoxal 5'-phosphate

Pyridoxal 5'-phosphate (Bound ligand (Het Group name = PLA) matches with 57.69% similarity)

• Enzyme class 2: E.C.2.6.1.3 - cysteine transaminase.
• Reaction: L-cysteine + 2-oxoglutarate = 2-oxo-3-sulfanylpropanoate + L-glutamate
• Cofactor: Pyridoxal 5'-phosphate

Pyridoxal 5'-phosphate (Bound ligand (Het Group name = PLA) matches with 57.69% similarity)

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

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

reference

DOI no: 10.1074/jbc.272.28.17293

J Biol Chem 272:17293-17302 (1997)

PubMed id: 9211866

Refinement and comparisons of the crystal structures of pig cytosolic aspartate aminotransferase and its complex with 2-methylaspartate.

S.Rhee, M.M.Silva, C.C.Hyde, P.H.Rogers, C.M.Metzler, D.E.Metzler, A.Arnone.

ABSTRACT

Two high resolution crystal structures of cytosolic aspartate aminotransferase from pig heart provide additional insights into the stereochemical mechanism for ligand-induced conformational changes in this enzyme. Structures of the homodimeric native structure and its complex with the substrate analog 2-methylaspartate have been refined, respectively, with 1.74-A x-ray diffraction data to an R value of 0.170, and with 1.6-A data to an R value of 0.173. In the presence of 2-methylaspartate, one of the subunits (subunit 1) shows a ligand-induced conformational change that involves a large movement of the small domain (residues 12-49 and 327-412) to produce a "closed" conformation. No such transition is observed in the other subunit (subunit 2), because crystal lattice contacts lock it in an "open" conformation like that adopted by subunit 1 in the absence of substrate. By comparing the open and closed forms of cAspAT, we propose a stereochemical mechanism for the open-to-closed transition that involves the electrostatic neutralization of two active site arginine residues by the negative charges of the incoming substrate, a large change in the backbone (phi,psi) conformational angles of two key glycine residues, and the entropy-driven burial of a stretch of hydrophobic residues on the N-terminal helix. The calculated free energy for the burial of this "hydrophobic plug" appears to be sufficient to serve as the driving force for domain closure.

Selected figure(s)

Figure 8.
Fig. 8. Atom labeling convention and definition of torsional angles for the internal aldimine.

Figure 9.
Fig. 9. Changes in the solvent-accessible surface area of subunit 1 residues (A) and subunit 2 residues (B) that are associated^ with the open-to-closed transition in subunit 1.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (1997, 272, 17293-17302) copyright 1997.

Figures were selected by an automated process.