1hxq
From Proteopedia
(New page: 200px<br /><applet load="1hxq" size="450" color="white" frame="true" align="right" spinBox="true" caption="1hxq, resolution 1.86Å" /> '''THE STRUCTURE OF NUC...) |
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| - | [[Image:1hxq.gif|left|200px]]<br /><applet load="1hxq" size=" | + | [[Image:1hxq.gif|left|200px]]<br /><applet load="1hxq" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1hxq, resolution 1.86Å" /> | caption="1hxq, resolution 1.86Å" /> | ||
'''THE STRUCTURE OF NUCLEOTIDYLATED GALACTOSE-1-PHOSPHATE URIDYLYLTRANSFERASE FROM ESCHERICHIA COLI AT 1.86 ANGSTROMS RESOLUTION'''<br /> | '''THE STRUCTURE OF NUCLEOTIDYLATED GALACTOSE-1-PHOSPHATE URIDYLYLTRANSFERASE FROM ESCHERICHIA COLI AT 1.86 ANGSTROMS RESOLUTION'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Galactose-1-phosphate uridylyltransferase catalyzes the reaction of | + | Galactose-1-phosphate uridylyltransferase catalyzes the reaction of UDP-glucose with galactose 1-phosphate to form UDP-galactose and glucose 1-phosphate during normal cellular metabolism. The reaction proceeds through a double displacement mechanism characterized by the formation of a stable nucleotidylated histidine intermediate. This paper describes the preparation of the uridylyl-enzyme complex on the crystalline enzyme from Escherichia coli and its subsequent structure determination by X-ray crystallography. The refined structure has an R-factor of 19.6% (data between 65 and 1.86 A resolution) and reveals modest conformational changes at the active site compared to the inactive UMP/UDP-enzyme complex reported previously [Wedekind, J.E., Frey, P.A., & Rayment, I. (1995) Biochemistry 34, 11049-11061]. In particular, positions of the respective UMP alpha-phosphoryl groups differ by approximately 4 A. Well-defined electron density for the nucleotidylated imidazole supports the existence of a covalent bond between N epsilon 2 of the nucleophile and the alpha-phosphorus of UMP. A hydrogen bond that is conserved in both complexes between His 166 N delta 1 and the carbonyl O of His 164 serves to properly orient the nucleophile and electrostatically stabilize the positively charged imidazolium that results from nucleotidylation. Hydrogen bonds from side-chain Gln 168 to the nonbridging phosphoryl oxygens of the nucleotidyl intermediate appear crucial for the formation and reaction of the uridylyl-enzyme complex as well. The significance of the latter interaction is underscored by the fact that the predominant cause of the metabolic disease galactosemia is the mutation of the corresponding Gln (Gln 188 in humans) to Arg. A comparison to other phosphohistidyl enzymes is described, as well as a revised model for the mechanism of the uridylyltransferase. |
==About this Structure== | ==About this Structure== | ||
| - | 1HXQ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with ZN, FE and U5P as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/UDP-glucose--hexose-1-phosphate_uridylyltransferase UDP-glucose--hexose-1-phosphate uridylyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.12 2.7.7.12] Full crystallographic information is available from [http:// | + | 1HXQ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=ZN:'>ZN</scene>, <scene name='pdbligand=FE:'>FE</scene> and <scene name='pdbligand=U5P:'>U5P</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/UDP-glucose--hexose-1-phosphate_uridylyltransferase UDP-glucose--hexose-1-phosphate uridylyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.12 2.7.7.12] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1HXQ OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: UDP-glucose--hexose-1-phosphate uridylyltransferase]] | [[Category: UDP-glucose--hexose-1-phosphate uridylyltransferase]] | ||
| - | [[Category: Frey, P | + | [[Category: Frey, P A.]] |
[[Category: Rayment, I.]] | [[Category: Rayment, I.]] | ||
| - | [[Category: Wedekind, J | + | [[Category: Wedekind, J E.]] |
[[Category: FE]] | [[Category: FE]] | ||
[[Category: U5P]] | [[Category: U5P]] | ||
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[[Category: reaction intermediate]] | [[Category: reaction intermediate]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:05:53 2008'' |
Revision as of 11:05, 21 February 2008
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THE STRUCTURE OF NUCLEOTIDYLATED GALACTOSE-1-PHOSPHATE URIDYLYLTRANSFERASE FROM ESCHERICHIA COLI AT 1.86 ANGSTROMS RESOLUTION
Overview
Galactose-1-phosphate uridylyltransferase catalyzes the reaction of UDP-glucose with galactose 1-phosphate to form UDP-galactose and glucose 1-phosphate during normal cellular metabolism. The reaction proceeds through a double displacement mechanism characterized by the formation of a stable nucleotidylated histidine intermediate. This paper describes the preparation of the uridylyl-enzyme complex on the crystalline enzyme from Escherichia coli and its subsequent structure determination by X-ray crystallography. The refined structure has an R-factor of 19.6% (data between 65 and 1.86 A resolution) and reveals modest conformational changes at the active site compared to the inactive UMP/UDP-enzyme complex reported previously [Wedekind, J.E., Frey, P.A., & Rayment, I. (1995) Biochemistry 34, 11049-11061]. In particular, positions of the respective UMP alpha-phosphoryl groups differ by approximately 4 A. Well-defined electron density for the nucleotidylated imidazole supports the existence of a covalent bond between N epsilon 2 of the nucleophile and the alpha-phosphorus of UMP. A hydrogen bond that is conserved in both complexes between His 166 N delta 1 and the carbonyl O of His 164 serves to properly orient the nucleophile and electrostatically stabilize the positively charged imidazolium that results from nucleotidylation. Hydrogen bonds from side-chain Gln 168 to the nonbridging phosphoryl oxygens of the nucleotidyl intermediate appear crucial for the formation and reaction of the uridylyl-enzyme complex as well. The significance of the latter interaction is underscored by the fact that the predominant cause of the metabolic disease galactosemia is the mutation of the corresponding Gln (Gln 188 in humans) to Arg. A comparison to other phosphohistidyl enzymes is described, as well as a revised model for the mechanism of the uridylyltransferase.
About this Structure
1HXQ is a Single protein structure of sequence from Escherichia coli with , and as ligands. Active as UDP-glucose--hexose-1-phosphate uridylyltransferase, with EC number 2.7.7.12 Full crystallographic information is available from OCA.
Reference
The structure of nucleotidylated histidine-166 of galactose-1-phosphate uridylyltransferase provides insight into phosphoryl group transfer., Wedekind JE, Frey PA, Rayment I, Biochemistry. 1996 Sep 10;35(36):11560-9. PMID:8794735
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