1lbm
From Proteopedia
(New page: 200px<br /><applet load="1lbm" size="450" color="white" frame="true" align="right" spinBox="true" caption="1lbm, resolution 2.8Å" /> '''CRYSTAL STRUCTURE OF ...) |
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| - | [[Image:1lbm.gif|left|200px]]<br /><applet load="1lbm" size=" | + | [[Image:1lbm.gif|left|200px]]<br /><applet load="1lbm" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1lbm, resolution 2.8Å" /> | caption="1lbm, resolution 2.8Å" /> | ||
'''CRYSTAL STRUCTURE OF PHOSPHORIBOSYL ANTHRANILATE ISOMERASE (PRAI) IN COMPLEX WITH REDUCED 1-(O-CARBOXYPHENYLAMINO)-1-DEOXYRIBULOSE 5-PHOSPHATE (RCDRP)'''<br /> | '''CRYSTAL STRUCTURE OF PHOSPHORIBOSYL ANTHRANILATE ISOMERASE (PRAI) IN COMPLEX WITH REDUCED 1-(O-CARBOXYPHENYLAMINO)-1-DEOXYRIBULOSE 5-PHOSPHATE (RCDRP)'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The enzymes | + | The enzymes N'-[(5'-phosphoribosyl)formimino]-5-aminoimidazole-4-carboxamide ribonucleotide isomerase (HisA) and phosphoribosylanthranilate isomerase (TrpF) are sugar isomerases that are involved in histidine and tryptophan biosynthesis, respectively. Both enzymes have the (betaalpha)(8)-barrel fold and catalyze Amadori rearrangements of a thermolabile aminoaldose into the corresponding aminoketose. To identify those amino acids that are essential for catalysis, conserved residues at the active sites of both HisA and TrpF from the hyperthermophile Thermotoga maritima were replaced by site-directed mutagenesis, and the purified variants were investigated by steady-state enzyme kinetics. Aspartate 8, aspartate 127, and threonine 164 appeared to be important for the HisA reaction, whereas cysteine 7 and aspartate 126 appeared to be important for the TrpF reaction. On the basis of these results and the X-ray structure of a complex between TrpF and a bound product analogue, a reaction mechanism involving general acid-base catalysis and a Schiff base intermediate is proposed for both enzymes. A comparison of the HisA and TrpF enzymes from T. maritima and Escherichia coli showed that, at the physiological temperatures of 80 and 37 degrees C, respectively, the enzymes from the hyperthermophile have significantly higher catalytic efficiencies than the corresponding enzymes from mesophiles. These results suggest that HisA and TrpF have similar chemical reaction mechanisms and use the same strategy to prevent the loss of their thermolabile substrates. |
==About this Structure== | ==About this Structure== | ||
| - | 1LBM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermotoga_maritima Thermotoga maritima] with 137 as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Phosphoribosylanthranilate_isomerase Phosphoribosylanthranilate isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.1.24 5.3.1.24] Full crystallographic information is available from [http:// | + | 1LBM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermotoga_maritima Thermotoga maritima] with <scene name='pdbligand=137:'>137</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Phosphoribosylanthranilate_isomerase Phosphoribosylanthranilate isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.1.24 5.3.1.24] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1LBM OCA]. |
==Reference== | ==Reference== | ||
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[[Category: tryptophan biosynthesis]] | [[Category: tryptophan biosynthesis]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:43:26 2008'' |
Revision as of 11:43, 21 February 2008
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CRYSTAL STRUCTURE OF PHOSPHORIBOSYL ANTHRANILATE ISOMERASE (PRAI) IN COMPLEX WITH REDUCED 1-(O-CARBOXYPHENYLAMINO)-1-DEOXYRIBULOSE 5-PHOSPHATE (RCDRP)
Overview
The enzymes N'-[(5'-phosphoribosyl)formimino]-5-aminoimidazole-4-carboxamide ribonucleotide isomerase (HisA) and phosphoribosylanthranilate isomerase (TrpF) are sugar isomerases that are involved in histidine and tryptophan biosynthesis, respectively. Both enzymes have the (betaalpha)(8)-barrel fold and catalyze Amadori rearrangements of a thermolabile aminoaldose into the corresponding aminoketose. To identify those amino acids that are essential for catalysis, conserved residues at the active sites of both HisA and TrpF from the hyperthermophile Thermotoga maritima were replaced by site-directed mutagenesis, and the purified variants were investigated by steady-state enzyme kinetics. Aspartate 8, aspartate 127, and threonine 164 appeared to be important for the HisA reaction, whereas cysteine 7 and aspartate 126 appeared to be important for the TrpF reaction. On the basis of these results and the X-ray structure of a complex between TrpF and a bound product analogue, a reaction mechanism involving general acid-base catalysis and a Schiff base intermediate is proposed for both enzymes. A comparison of the HisA and TrpF enzymes from T. maritima and Escherichia coli showed that, at the physiological temperatures of 80 and 37 degrees C, respectively, the enzymes from the hyperthermophile have significantly higher catalytic efficiencies than the corresponding enzymes from mesophiles. These results suggest that HisA and TrpF have similar chemical reaction mechanisms and use the same strategy to prevent the loss of their thermolabile substrates.
About this Structure
1LBM is a Single protein structure of sequence from Thermotoga maritima with as ligand. Active as Phosphoribosylanthranilate isomerase, with EC number 5.3.1.24 Full crystallographic information is available from OCA.
Reference
Two (betaalpha)(8)-barrel enzymes of histidine and tryptophan biosynthesis have similar reaction mechanisms and common strategies for protecting their labile substrates., Henn-Sax M, Thoma R, Schmidt S, Hennig M, Kirschner K, Sterner R, Biochemistry. 2002 Oct 8;41(40):12032-42. PMID:12356303
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