2qm6
From Proteopedia
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'''Crystal Structure of Helicobacter Pylori Gamma-Glutamyltranspeptidase in Complex with Glutamate''' | '''Crystal Structure of Helicobacter Pylori Gamma-Glutamyltranspeptidase in Complex with Glutamate''' | ||
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[[Category: Boanca, G.]] | [[Category: Boanca, G.]] | ||
[[Category: Sand, A.]] | [[Category: Sand, A.]] | ||
| - | [[Category: | + | [[Category: Glutamyltranspeptidase]] |
| - | [[Category: | + | [[Category: Ntn-hydrolase]] |
| - | [[Category: | + | [[Category: Transferase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 15:11:31 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 12:11, 4 May 2008
Crystal Structure of Helicobacter Pylori Gamma-Glutamyltranspeptidase in Complex with Glutamate
Overview
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.
About this Structure
2QM6 is a Protein complex structure of sequences from Helicobacter pylori. Full crystallographic information is available from OCA.
Reference
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., Morrow AL, Williams K, Sand A, Boanca G, Barycki JJ, Biochemistry. 2007 Nov 20;46(46):13407-14. Epub 2007 Oct 26. PMID:17960917 Page seeded by OCA on Sun May 4 15:11:31 2008
