1qk5
From Proteopedia
(New page: 200px<br /><applet load="1qk5" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qk5, resolution 1.60Å" /> '''TOXOPLASMA GONDII HY...) |
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| - | [[Image:1qk5.gif|left|200px]]<br /><applet load="1qk5" size=" | + | [[Image:1qk5.gif|left|200px]]<br /><applet load="1qk5" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1qk5, resolution 1.60Å" /> | caption="1qk5, resolution 1.60Å" /> | ||
'''TOXOPLASMA GONDII HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE WITH XMP, PYROPHOSPHATE AND TWO MG2+ IONS'''<br /> | '''TOXOPLASMA GONDII HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE WITH XMP, PYROPHOSPHATE AND TWO MG2+ IONS'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The crystal structure of the Toxoplasma gondii hypoxanthine-guanine | + | The crystal structure of the Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-xanthosine 5'-monophosphate (XMP)-pyrophosphate-Mg(2+) ternary complex has been determined at 1. 60 A resolution. This biproduct, post-transition state structure is of a T. gondii HGPRT mutant (Asp150Ala or D150A). The D150A mutant has reduced activity (k(cat) lower by 11-, 296-, and 8.6-fold for hypoxanthine, guanine, and xanthine, respectively) compared to wild-type T. gondii HGPRT. The Michaelis constants for purine bases are altered only slightly, whereas those for alpha-D-5-phosphoribosyl 1-pyrophosphate (PRPP) are lower by approximately 6.5-fold. The ternary complex crystallizes in space group C222(1) (a = 55.21 A, b = 112.25 A, and c = 144.28 A) with two subunits in the asymmetric unit; the HGPRT tetramer is completed by the application of 2-fold crystallographic symmetry. All active sites contain XMP inverted question markbound in a fashion similar to that of the guanosine 5'-monophosphate (GMP) and inosine 5'-monophosphate (IMP) complexes reported in the preceding article [Heroux, A., et al. (1999) Biochemistry 38, 14485-14494] inverted question mark, pyrophosphate, and two Mg(2+) ions. Each Mg(2+) ion is octahedrally coordinated by two terminal pyrophosphate oxygen atoms and several ordered water molecules. This structure shows how HGPRT uses two Mg(2+) ions to orient and activate the pyrophosphate moiety of PRPP for attack by a purine base, and why mutation in humans of the residue corresponding to Asp206, the only HGPRT amino acid that directly contacts the Mg(2+) ions, causes Lesch-Nyhan syndrome (HGPRT(Kinston), D193N). The Leu78-Lys79 peptide bond in the active site adopts the cis configuration, which it must to bind PRPP or pyrophosphate. The contribution of cis-trans isomerization of this peptide bond to the energetics of substrate binding and product release is discussed. A comprehensive description of the HGPRT reaction mechanism is also proposed. |
==About this Structure== | ==About this Structure== | ||
| - | 1QK5 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Toxoplasma_gondii Toxoplasma gondii] with MG, XMP and POP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Hypoxanthine_phosphoribosyltransferase Hypoxanthine phosphoribosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.2.8 2.4.2.8] Full crystallographic information is available from [http:// | + | 1QK5 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Toxoplasma_gondii Toxoplasma gondii] with <scene name='pdbligand=MG:'>MG</scene>, <scene name='pdbligand=XMP:'>XMP</scene> and <scene name='pdbligand=POP:'>POP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Hypoxanthine_phosphoribosyltransferase Hypoxanthine phosphoribosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.2.8 2.4.2.8] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1QK5 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Toxoplasma gondii]] | [[Category: Toxoplasma gondii]] | ||
| - | [[Category: Borhani, D | + | [[Category: Borhani, D W.]] |
| - | [[Category: Davis, R | + | [[Category: Davis, R L.]] |
[[Category: Heroux, A.]] | [[Category: Heroux, A.]] | ||
| - | [[Category: Ross, L | + | [[Category: Ross, L J.]] |
| - | [[Category: White, E | + | [[Category: White, E L.]] |
[[Category: MG]] | [[Category: MG]] | ||
[[Category: POP]] | [[Category: POP]] | ||
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[[Category: transferase]] | [[Category: transferase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:40:32 2008'' |
Revision as of 12:40, 21 February 2008
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TOXOPLASMA GONDII HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE WITH XMP, PYROPHOSPHATE AND TWO MG2+ IONS
Overview
The crystal structure of the Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-xanthosine 5'-monophosphate (XMP)-pyrophosphate-Mg(2+) ternary complex has been determined at 1. 60 A resolution. This biproduct, post-transition state structure is of a T. gondii HGPRT mutant (Asp150Ala or D150A). The D150A mutant has reduced activity (k(cat) lower by 11-, 296-, and 8.6-fold for hypoxanthine, guanine, and xanthine, respectively) compared to wild-type T. gondii HGPRT. The Michaelis constants for purine bases are altered only slightly, whereas those for alpha-D-5-phosphoribosyl 1-pyrophosphate (PRPP) are lower by approximately 6.5-fold. The ternary complex crystallizes in space group C222(1) (a = 55.21 A, b = 112.25 A, and c = 144.28 A) with two subunits in the asymmetric unit; the HGPRT tetramer is completed by the application of 2-fold crystallographic symmetry. All active sites contain XMP inverted question markbound in a fashion similar to that of the guanosine 5'-monophosphate (GMP) and inosine 5'-monophosphate (IMP) complexes reported in the preceding article [Heroux, A., et al. (1999) Biochemistry 38, 14485-14494] inverted question mark, pyrophosphate, and two Mg(2+) ions. Each Mg(2+) ion is octahedrally coordinated by two terminal pyrophosphate oxygen atoms and several ordered water molecules. This structure shows how HGPRT uses two Mg(2+) ions to orient and activate the pyrophosphate moiety of PRPP for attack by a purine base, and why mutation in humans of the residue corresponding to Asp206, the only HGPRT amino acid that directly contacts the Mg(2+) ions, causes Lesch-Nyhan syndrome (HGPRT(Kinston), D193N). The Leu78-Lys79 peptide bond in the active site adopts the cis configuration, which it must to bind PRPP or pyrophosphate. The contribution of cis-trans isomerization of this peptide bond to the energetics of substrate binding and product release is discussed. A comprehensive description of the HGPRT reaction mechanism is also proposed.
About this Structure
1QK5 is a Single protein structure of sequence from Toxoplasma gondii with , and as ligands. Active as Hypoxanthine phosphoribosyltransferase, with EC number 2.4.2.8 Full crystallographic information is available from OCA.
Reference
Crystal structure of Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase with XMP, pyrophosphate, and two Mg(2+) ions bound: insights into the catalytic mechanism., Heroux A, White EL, Ross LJ, Davis RL, Borhani DW, Biochemistry. 1999 Nov 2;38(44):14495-506. PMID:10545171
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