1xg4
From Proteopedia
(New page: 200px<br /><applet load="1xg4" size="450" color="white" frame="true" align="right" spinBox="true" caption="1xg4, resolution 1.6Å" /> '''Crystal Structure of ...) |
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| - | [[Image:1xg4.gif|left|200px]]<br /><applet load="1xg4" size=" | + | [[Image:1xg4.gif|left|200px]]<br /><applet load="1xg4" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1xg4, resolution 1.6Å" /> | caption="1xg4, resolution 1.6Å" /> | ||
'''Crystal Structure of the C123S 2-Methylisocitrate Lyase Mutant from Escherichia coli in complex with the inhibitor isocitrate'''<br /> | '''Crystal Structure of the C123S 2-Methylisocitrate Lyase Mutant from Escherichia coli in complex with the inhibitor isocitrate'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Two crystal structures of the C123S mutant of 2-methylisocitrate lyase | + | Two crystal structures of the C123S mutant of 2-methylisocitrate lyase have been determined, one with the bound reaction products, Mg(2+)-pyruvate and succinate, and the second with a bound Mg(2+)-(2R,3S)-isocitrate inhibitor. Comparison with the structure of the wild-type enzyme in the unbound state reveals that the enzyme undergoes a conformational transition that sequesters the ligand from solvent, as previously observed for two other enzyme superfamily members, isocitrate lyase and phosphoenolpyruvate mutase. The binding modes reveal the determinants of substrate specificity and stereoselectivity, and the stringent specificity is verified in solution using various potential substrates. A model of bound 2-methylisocitrate has been developed based on the experimentally determined structures. We propose a catalytic mechanism involving an alpha-carboxy-carbanion intermediate/transition state, which is consistent with previous stereochemical experiments showing inversion of configuration at the C(3) of 2-methylisocitrate. Structure-based sequence analysis and phylogenic tree construction reveal determinants of substrate specificity, highlight nodes of divergence of families, and predict enzyme families with new functions. |
==About this Structure== | ==About this Structure== | ||
| - | 1XG4 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 MG and ICT as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Methylisocitrate_lyase Methylisocitrate lyase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.3.30 4.1.3.30] Full crystallographic information is available from [http:// | + | 1XG4 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=MG:'>MG</scene> and <scene name='pdbligand=ICT:'>ICT</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Methylisocitrate_lyase Methylisocitrate lyase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.3.30 4.1.3.30] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XG4 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: isocitrate lyase superfamily]] | [[Category: isocitrate lyase superfamily]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:54:24 2008'' |
Revision as of 13:54, 21 February 2008
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Crystal Structure of the C123S 2-Methylisocitrate Lyase Mutant from Escherichia coli in complex with the inhibitor isocitrate
Overview
Two crystal structures of the C123S mutant of 2-methylisocitrate lyase have been determined, one with the bound reaction products, Mg(2+)-pyruvate and succinate, and the second with a bound Mg(2+)-(2R,3S)-isocitrate inhibitor. Comparison with the structure of the wild-type enzyme in the unbound state reveals that the enzyme undergoes a conformational transition that sequesters the ligand from solvent, as previously observed for two other enzyme superfamily members, isocitrate lyase and phosphoenolpyruvate mutase. The binding modes reveal the determinants of substrate specificity and stereoselectivity, and the stringent specificity is verified in solution using various potential substrates. A model of bound 2-methylisocitrate has been developed based on the experimentally determined structures. We propose a catalytic mechanism involving an alpha-carboxy-carbanion intermediate/transition state, which is consistent with previous stereochemical experiments showing inversion of configuration at the C(3) of 2-methylisocitrate. Structure-based sequence analysis and phylogenic tree construction reveal determinants of substrate specificity, highlight nodes of divergence of families, and predict enzyme families with new functions.
About this Structure
1XG4 is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Methylisocitrate lyase, with EC number 4.1.3.30 Full crystallographic information is available from OCA.
Reference
Crystal structures of 2-methylisocitrate lyase in complex with product and with isocitrate inhibitor provide insight into lyase substrate specificity, catalysis and evolution., Liu S, Lu Z, Han Y, Melamud E, Dunaway-Mariano D, Herzberg O, Biochemistry. 2005 Mar 1;44(8):2949-62. PMID:15723538
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