PDBsum entry 1v4g

Ligase

PDB id: 1v4g

Contents

Protein chains

509 a.a.

Waters ×313

References listed in PDB file

Key reference

Title

Crystal structure of gamma-Glutamylcysteine synthetase: insights into the mechanism of catalysis by a key enzyme for glutathione homeostasis.

Authors

T.Hibi, H.Nii, T.Nakatsu, A.Kimura, H.Kato, J.Hiratake, J.Oda.

Ref.

Proc Natl Acad Sci U S A, 2004, 101, 15052-15057. [DOI no: 10.1073/pnas.0403277101]

PubMed id

15477603

Abstract

Gamma-glutamylcysteine synthetase (gammaGCS), a rate-limiting enzyme in glutathione biosynthesis, plays a central role in glutathione homeostasis and is a target for development of potential therapeutic agents against parasites and cancer. We have determined the crystal structures of Escherichia coli gammaGCS unliganded and complexed with a sulfoximine-based transition-state analog inhibitor at resolutions of 2.5 and 2.1 A, respectively. In the crystal structure of the complex, the bound inhibitor is phosphorylated at the sulfoximido nitrogen and is coordinated to three Mg2+ ions. The cysteine-binding site was identified; it is formed inductively at the transition state. In the unliganded structure, an open space exists around the representative cysteine-binding site and is probably responsible for the competitive binding of glutathione. Upon inhibitor binding, the side chains of Tyr-241 and Tyr-300 turn, forming a hydrogen-bonding triad with the carboxyl group of the inhibitor's cysteine moiety, allowing this moiety to fit tightly into the cysteine-binding site with concomitant accommodation of its side chain into a shallow pocket. This movement is caused by a conformational change of a switch loop (residues 240-249). Based on this crystal structure, the cysteine-binding sites of mammalian and parasitic gammaGCSs were predicted by multiple sequence alignment, although no significant sequence identity exists between the E. coli gammaGCS and its eukaryotic homologues. The identification of this cysteine-binding site provides important information for the rational design of novel gammaGCS inhibitors.

Figure 3.
Fig. 3. Stereoview of the residues surrounding the Cys-analog moiety of sulfoximine 2, showing the distances between the ligands. The molecular surface around the Cys-binding site is drawn in white.

Figure 5.
Fig. 5. Superimposition of residues 238-251, including the switch loop. The loop's hinge residues, Gly-240 and Leu-249, are labeled.

Secondary reference #1

Title

Escherichia coli b gamma-Glutamylcysteine synthetase: modification, Purification, Crystallization and preliminary crystallographic analysis.

Authors

T.Hibi, H.Hisada, T.Nakatsu, H.Kato, J.Oda.

Ref.

Acta Crystallogr D Biol Crystallogr, 2002, 58, 316-318. [DOI no: 10.1107/S0907444901019886]

PubMed id

11807262

Figure 2.
Figure 2 The self-rotation function of GCS at angles of (a) 180° and (b) 120°. The data are in the resolution range 10.0-3.0 Å and the integration radius is 30.0 Å.

The above figure is reproduced from the cited reference with permission from the IUCr