1g4e: Difference between revisions
New page: left|200px<br /><applet load="1g4e" size="450" color="white" frame="true" align="right" spinBox="true" caption="1g4e, resolution 1.60Å" /> '''THIAMIN PHOSPHATE SY... |
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[[Image:1g4e.jpg|left|200px]]<br /><applet load="1g4e" size=" | [[Image:1g4e.jpg|left|200px]]<br /><applet load="1g4e" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1g4e, resolution 1.60Å" /> | caption="1g4e, resolution 1.60Å" /> | ||
'''THIAMIN PHOSPHATE SYNTHASE'''<br /> | '''THIAMIN PHOSPHATE SYNTHASE'''<br /> | ||
==Overview== | ==Overview== | ||
Thiamin phosphate synthase catalyzes the formation of thiamin phosphate | Thiamin phosphate synthase catalyzes the formation of thiamin phosphate from 4-amino-5-(hydroxymethyl)-2-methylpyrimidine pyrophosphate and 5-(hydroxyethyl)-4-methylthiazole phosphate. Several lines of evidence suggest that the reaction proceeds via a dissociative mechanism. The previously determined crystal structure of thiamin phosphate synthase in complex with the reaction products, thiamin phosphate and magnesium pyrophosphate, provided a view of the active site and suggested a number of additional experiments. We report here seven new crystal structures primarily involving crystals of S130A thiamin phosphate synthase soaked in solutions containing substrates or products. We prepared S130A thiamin phosphate synthase with the intent of characterizing the enzyme-substrate complex. Surprisingly, in three thiamin phosphate synthase structures, the active site density cannot be modeled as either substrates or products. For these structures, the best fit to the electron density is provided by a model that consists of independent pyrimidine, pyrophosphate, and thiazole phosphate fragments, consistent with a carbenium ion intermediate. The resulting carbenium ion is likely to be further stabilized by proton transfer from the pyrimidine amino group to the pyrophosphate to give the pyrimidine iminemethide, which we believe is the species that is observed in the crystal structures. | ||
==About this Structure== | ==About this Structure== | ||
1G4E is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis]. Active as [http://en.wikipedia.org/wiki/Thiamine-phosphate_diphosphorylase Thiamine-phosphate diphosphorylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.5.1.3 2.5.1.3] Full crystallographic information is available from [http:// | 1G4E is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis]. Active as [http://en.wikipedia.org/wiki/Thiamine-phosphate_diphosphorylase Thiamine-phosphate diphosphorylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.5.1.3 2.5.1.3] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1G4E OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Thiamine-phosphate diphosphorylase]] | [[Category: Thiamine-phosphate diphosphorylase]] | ||
[[Category: Begley, T | [[Category: Begley, T P.]] | ||
[[Category: Campobasso, N.]] | [[Category: Campobasso, N.]] | ||
[[Category: Chiu, H | [[Category: Chiu, H J.]] | ||
[[Category: Ealick, S | [[Category: Ealick, S E.]] | ||
[[Category: Peapus, D | [[Category: Peapus, D H.]] | ||
[[Category: Reddick, J | [[Category: Reddick, J J.]] | ||
[[Category: thiamin biosynthesis]] | [[Category: thiamin biosynthesis]] | ||
[[Category: tim barrel]] | [[Category: tim barrel]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:46:04 2008'' | ||
Revision as of 13:46, 21 February 2008
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THIAMIN PHOSPHATE SYNTHASE
OverviewOverview
Thiamin phosphate synthase catalyzes the formation of thiamin phosphate from 4-amino-5-(hydroxymethyl)-2-methylpyrimidine pyrophosphate and 5-(hydroxyethyl)-4-methylthiazole phosphate. Several lines of evidence suggest that the reaction proceeds via a dissociative mechanism. The previously determined crystal structure of thiamin phosphate synthase in complex with the reaction products, thiamin phosphate and magnesium pyrophosphate, provided a view of the active site and suggested a number of additional experiments. We report here seven new crystal structures primarily involving crystals of S130A thiamin phosphate synthase soaked in solutions containing substrates or products. We prepared S130A thiamin phosphate synthase with the intent of characterizing the enzyme-substrate complex. Surprisingly, in three thiamin phosphate synthase structures, the active site density cannot be modeled as either substrates or products. For these structures, the best fit to the electron density is provided by a model that consists of independent pyrimidine, pyrophosphate, and thiazole phosphate fragments, consistent with a carbenium ion intermediate. The resulting carbenium ion is likely to be further stabilized by proton transfer from the pyrimidine amino group to the pyrophosphate to give the pyrimidine iminemethide, which we believe is the species that is observed in the crystal structures.
About this StructureAbout this Structure
1G4E is a Single protein structure of sequence from Bacillus subtilis. Active as Thiamine-phosphate diphosphorylase, with EC number 2.5.1.3 Full crystallographic information is available from OCA.
ReferenceReference
Structural characterization of the enzyme-substrate, enzyme-intermediate, and enzyme-product complexes of thiamin phosphate synthase., Peapus DH, Chiu HJ, Campobasso N, Reddick JJ, Begley TP, Ealick SE, Biochemistry. 2001 Aug 28;40(34):10103-14. PMID:11513589
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