PDBsum entry 2gwd

Ligase

PDB id: 2gwd

Contents

Protein chain

436 a.a. *

Ligands

ACT ×5

GLU

Metals

_MG

Waters ×245

* Residue conservation analysis

PDB id:

2gwd

Name:

Ligase

Title:

Crystal structure of plant glutamate cysteine ligase in complex with mg2+ and l-glutamate

Structure:

Glutamate cysteine ligase. Chain: a. Fragment: glutamate cysteine ligase. Synonym: gamma-glutamylcysteine synthetase, gamma-ecs, gcs. Engineered: yes

Source:

Brassica juncea. Organism_taxid: 3707. Gene: gsh1. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.09Å R-factor: 0.178 R-free: 0.227

Authors:

M.Hothorn,A.Wachter,R.Gromes,T.Stuwe,T.Rausch,K.Scheffzek

Key ref:

M.Hothorn et al. (2006). Structural basis for the redox control of plant glutamate cysteine ligase. J Biol Chem, 281, 27557-27565. PubMed id: 16766527 DOI: 10.1074/jbc.M602770200

Date:

04-May-06 Release date: 20-Jun-06

Protein chain

O23736  (GSH1_BRAJU) -  Glutamate--cysteine ligase, chloroplastic from Brassica juncea

Seq: 514 a.a.

Struc: 436 a.a.

Enzyme reactions

• Enzyme class: E.C.6.3.2.2 - glutamate--cysteine ligase.
• Reaction: L-cysteine + L-glutamate + ATP = gamma-L-glutamyl-L-cysteine + ADP + phosphate + H⁺

L-cysteine + L-glutamate + ATP (Bound ligand (Het Group name = GLU) corresponds exactly) = gamma-L-glutamyl-L-cysteine + ADP + phosphate + H(+)

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

reference

DOI no: 10.1074/jbc.M602770200

J Biol Chem 281:27557-27565 (2006)

PubMed id: 16766527

Structural basis for the redox control of plant glutamate cysteine ligase.

M.Hothorn, A.Wachter, R.Gromes, T.Stuwe, T.Rausch, K.Scheffzek.

ABSTRACT

Glutathione (GSH) plays a crucial role in plant metabolism and stress response. The rate-limiting step in the biosynthesis of GSH is catalyzed by glutamate cysteine ligase (GCL) the activity of which is tightly regulated. The regulation of plant GCLs is poorly understood. The crystal structure of substrate-bound GCL from Brassica juncea at 2.1-A resolution reveals a plant-unique regulatory mechanism based on two intramolecular redox-sensitive disulfide bonds. Reduction of one disulfide bond allows a beta-hairpin motif to shield the active site of B. juncea GCL, thereby preventing the access of substrates. Reduction of the second disulfide bond reversibly controls dimer to monomer transition of B. juncea GCL that is associated with a significant inactivation of the enzyme. These regulatory events provide a molecular link between high GSH levels in the plant cell and associated down-regulation of its biosynthesis. Furthermore, known mutations in the Arabidopsis GCL gene affect residues in the close proximity of the active site and thus explain the decreased GSH levels in mutant plants. In particular, the mutation in rax1-1 plants causes impaired binding of cysteine.

Selected figure(s)

Figure 1.
FIGURE 1. Plant GCL shows unique structural features. Front and side views of BjGCL shown in ribbon representation. The central -sheet is depicted in dark blue, the N- and C-terminal helical regions in light blue, and the plant unique arms in dark and light green, respectively. The L-glutamate bound in the active site is represented in bond representation along with the Mg^2+ ion (in cyan). The two disulfide bridges CC1 and CC2 are highlighted in yellow; the -hairpin module is shown in red.

Figure 2.
FIGURE 2. Substrate binding in plant GCL. A, close-up view of the glutamate binding site with the inhibitor BSO (in yellow; sulfur depicted in magenta) in bond representation and including the final 2F[obs] - F[calc] electron density map contoured at 1.5 . Residues reaching from the central -sheet (in blue) to coordinate the Mg^2+ ion (in cyan) are depicted in blue. Residues contributed by the helical arms are shown in light green. B, schematic representation of the inhibitor BSO binding to BjGCL. The LigPlot diagram (50) summarizes key interactions between the BSO ligand and active site residues. Yellow lines, BSO ligand; green lines, BjGCL residues; semicircles with radiating lines; atoms or residues involved in hydrophobic contacts between protein and ligand. C, stereo close-up view of the plant GCL cysteine binding pocket formed by mostly hydrophobic residues (in blue) around the aliphatic side chain of BSO (in light gray). The corresponding secondary structure elements and residues in E. coli GCL (PDB-ID: 1VA6) are shown in orange. D, known mutations in the Arabidopsis GCL gene are in proximity of the substrate binding sites in plant GCL. BjGCL in ribbon representation is shown with BSO and ADP (modeled) in bonds representation (in yellow). Small spheres indicate the positions of residues affected in AtGCL mutant plants (in magenta). Enlarged versions provide models on how the affected residues in rax1-1 and rml1 mutants may interact with GCL substrates. The rax1-1 arginine residue (Arg^220) is shown in a modeled rotamer configuration bringing its guanidinium group in close proximity to the terminal methyl of BSO that corresponds to the sulfhydryl group of cysteine (in green). Interactions are highlighted by dotted lines (in magenta).

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2006, 281, 27557-27565) copyright 2006.

Figures were selected by an automated process.