1e77
From Proteopedia
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==Overview== | ==Overview== | ||
| - | The role of Asp-177 in the His-Asp catalytic dyad of glucose 6-phosphate | + | The role of Asp-177 in the His-Asp catalytic dyad of glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides has been investigated by a structural and functional characterization of the D177N mutant enzyme. Its three-dimensional structure has been determined by X-ray cryocrystallography in the presence of NAD(+) and in the presence of glucose 6-phosphate plus NADPH. The structure of a glucose 6-phosphate complex of a mutant (Q365C) with normal enzyme activity has also been determined and substrate binding compared. To understand the effect of Asp-177 on the ionization properties of the catalytic base His-240, the pH dependence of kinetic parameters has been determined for the D177N mutant and compared to that of the wild-type enzyme. The structures give details of glucose 6-phosphate binding and show that replacement of the Asp-177 of the catalytic dyad with asparagine does not affect the overall structure of glucose 6-phosphate dehydrogenase. Additionally, the evidence suggests that the productive tautomer of His-240 in the D177N mutant enzyme is stabilized by a hydrogen bond with Asn-177; hence, the mutation does not affect tautomer stabilization. We conclude, therefore, that the absence of a negatively charged aspartate at 177 accounts for the decrease in catalytic activity at pH 7.8. Structural analysis suggests that the pH dependence of the kinetic parameters of D177N glucose 6-phosphate dehydrogenase results from an ionized water molecule replacing the missing negative charge of the mutated Asp-177 at high pH. Glucose 6-phosphate binding orders and orients His-178 in the D177N-glucose 6-phosphate-NADPH ternary complex and appears to be necessary to form this water-binding site. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Leuconostoc mesenteroides]] | [[Category: Leuconostoc mesenteroides]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Adams, M | + | [[Category: Adams, M J.]] |
[[Category: Gover, S.]] | [[Category: Gover, S.]] | ||
[[Category: Vandeputte-Rutten, L.]] | [[Category: Vandeputte-Rutten, L.]] | ||
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[[Category: oxidoreductase (choh(d) - nad(p))]] | [[Category: oxidoreductase (choh(d) - nad(p))]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:24:38 2008'' |
Revision as of 10:24, 21 February 2008
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COMPLEX OF ACTIVE MUTANT (Q365->C) OF GLUCOSE 6-PHOSPHATE DEHYDROGENASE FROM LEUCONOSTOC MESENTEROIDES WITH SUBSTRATE
Overview
The role of Asp-177 in the His-Asp catalytic dyad of glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides has been investigated by a structural and functional characterization of the D177N mutant enzyme. Its three-dimensional structure has been determined by X-ray cryocrystallography in the presence of NAD(+) and in the presence of glucose 6-phosphate plus NADPH. The structure of a glucose 6-phosphate complex of a mutant (Q365C) with normal enzyme activity has also been determined and substrate binding compared. To understand the effect of Asp-177 on the ionization properties of the catalytic base His-240, the pH dependence of kinetic parameters has been determined for the D177N mutant and compared to that of the wild-type enzyme. The structures give details of glucose 6-phosphate binding and show that replacement of the Asp-177 of the catalytic dyad with asparagine does not affect the overall structure of glucose 6-phosphate dehydrogenase. Additionally, the evidence suggests that the productive tautomer of His-240 in the D177N mutant enzyme is stabilized by a hydrogen bond with Asn-177; hence, the mutation does not affect tautomer stabilization. We conclude, therefore, that the absence of a negatively charged aspartate at 177 accounts for the decrease in catalytic activity at pH 7.8. Structural analysis suggests that the pH dependence of the kinetic parameters of D177N glucose 6-phosphate dehydrogenase results from an ionized water molecule replacing the missing negative charge of the mutated Asp-177 at high pH. Glucose 6-phosphate binding orders and orients His-178 in the D177N-glucose 6-phosphate-NADPH ternary complex and appears to be necessary to form this water-binding site.
About this Structure
1E77 is a Single protein structure of sequence from Leuconostoc mesenteroides with and as ligands. Active as Glucose-6-phosphate 1-dehydrogenase, with EC number 1.1.1.49 Known structural/functional Sites: and . Full crystallographic information is available from OCA.
Reference
An examination of the role of asp-177 in the His-Asp catalytic dyad of Leuconostoc mesenteroides glucose 6-phosphate dehydrogenase: X-ray structure and pH dependence of kinetic parameters of the D177N mutant enzyme., Cosgrove MS, Gover S, Naylor CE, Vandeputte-Rutten L, Adams MJ, Levy HR, Biochemistry. 2000 Dec 12;39(49):15002-11. PMID:11106478
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