2QM6

Crystal Structure of Helicobacter Pylori Gamma-Glutamyltranspeptidase in Complex with Glutamate

Summary for 2QM6

• Entry DOI: 10.2210/pdb2qm6/pdb
• Related: 2NQO 2QMC
• Descriptor: Gamma-glutamyltranspeptidase, GLUTAMIC ACID, ... (4 entities in total)
• Functional Keywords: ntn-hydrolase, glutamyltranspeptidase, transferase
• Biological source: Helicobacter pylori; More
• Total number of polymer chains: 4
• Total formula weight: 122269.39

Authors

Barycki, J.J.,Sand, A.,Boanca, G. (deposition date: 2007-07-14, release date: 2008-02-12, Last modification date: 2023-08-30)

Primary citation

Morrow, A.L.,Williams, K.,Sand, A.,Boanca, G.,Barycki, J.J.
Characterization of Helicobacter pylori gamma-glutamyltranspeptidase reveals the molecular basis for substrate specificity and a critical role for the tyrosine 433-containing loop in catalysis.
Biochemistry, 46:13407-13414, 2007

PubMed Abstract: Helicobacter pylori gamma-glutamyltranspeptidase (HpGT) is a member of the N-terminal nucleophile hydrolase superfamily. It is translated as an inactive 60 kDa polypeptide precursor that undergoes intramolecular autocatalytic cleavage to generate a fully active heterodimer composed of a 40 kDa and a 20 kDa subunit. The resultant N-terminus, Thr 380, has been shown to be the catalytic nucleophile in both autoprocessing and enzymatic reactions. Once processed, HpGT catalyzes the hydrolysis of the gamma-glutamyl bond in glutathione and its conjugates. To facilitate the determination of physiologically relevant substrates for the enzyme, crystal structures of HpGT in complex with glutamate (1.6 A, Rfactor = 16.7%, Rfree = 19.0%) and an inactive HpGT mutant, T380A, in complex with S-(nitrobenzyl)glutathione (1.55 A, Rfactor = 18.7%, Rfree = 21.8%) have been determined. Residues that comprise the gamma-glutamyl binding site are primarily located in the 20 kDa subunit and make numerous hydrogen bonds with the alpha-amino and alpha-carboxylate groups of the substrate. In contrast, a single hydrogen bond occurs between the T380A mutant and the remainder of the ligand. Lack of specific coordination beyond the gamma-glutamyl moiety may account for the substrate binding permissiveness of the enzyme. Structural analysis was combined with site-directed mutagenesis of residues involved in maintaining the conformation of a loop region that covers the gamma-glutamyl binding site. Results provide evidence that access to this buried site may occur through conformational changes in the Tyr 433-containing loop, as disruption of the intricate hydrogen-bond network responsible for optimal placement of Tyr 433 significantly diminishes catalytic activity.

PubMed: 17960917
DOI: 10.1021/bi701599e

Experimental method

X-RAY DIFFRACTION (1.6 Å)