1a9y: Difference between revisions

Revision as of 10:01, 2 May 2008

UDP-GALACTOSE 4-EPIMERASE MUTANT S124A/Y149F COMPLEXED WITH UDP-GLUCOSE

OverviewOverview

UDP-galactose 4-epimerase catalyzes the interconversion of UDP-galactose and UDP-glucose during normal galactose metabolism. Within recent years the enzyme from Escherichia coli has been studied extensively by both biochemical and X-ray crystallographic techniques. One of several key features in the catalytic mechanism of the enzyme involves the putative rotation of a 4'-ketopyranose intermediate within the active site region. The mode of binding of UDP-glucose to epimerase is well understood on the basis of previous high-resolution X-ray crystallographic investigations from this laboratory with an enzyme/NADH/UDP-glucose abortive complex. Attempts to prepare an enzyme/NADH/UDP-galactose abortive complex always failed, however, in that UDP-glucose rather than UDP-galactose was observed binding in the active site. In an effort to prepare an abortive complex with UDP-galactose, a site-directed mutant protein was constructed in which Ser 124 and Tyr 149, known to play critical roles in catalysis, were substituted with alanine and phenylalanine residues, respectively. With this double mutant it was possible to crystallize and solve the three-dimensional structures of reduced epimerase in the presence of UDP-glucose or UDP-galactose to high resolution. This study represents the first direct observation of UDP-galactose binding to epimerase and lends strong structural support for a catalytic mechanism in which there is free rotation of a 4'-ketopyranose intermediate within the active site cleft of the enzyme.

About this StructureAbout this Structure

1A9Y is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

ReferenceReference

Dramatic differences in the binding of UDP-galactose and UDP-glucose to UDP-galactose 4-epimerase from Escherichia coli., Thoden JB, Holden HM, Biochemistry. 1998 Aug 18;37(33):11469-77. PMID:9708982 Page seeded by OCA on Fri May 2 10:01:46 2008

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OCA

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 [[Image:1a9y.gif|left|200px]]
- {{Structure
+<!--
-|PDB= 1a9y |SIZE=350|CAPTION= <scene name='initialview01'>1a9y</scene>, resolution 1.8&Aring;
+The line below this paragraph, containing "STRUCTURE_1a9y", creates the "Structure Box" on the page.
-|SITE=
+You may change the PDB parameter (which sets the PDB file loaded into the applet)
-|LIGAND= <scene name='pdbligand=NA:SODIUM+ION'>NA</scene>, <scene name='pdbligand=NAD:NICOTINAMIDE-ADENINE-DINUCLEOTIDE'>NAD</scene>, <scene name='pdbligand=UPG:URIDINE-5&#39;-DIPHOSPHATE-GLUCOSE'>UPG</scene>
+or the SCENE parameter (which sets the initial scene displayed when the page is loaded),
-|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/UDP-glucose_4-epimerase UDP-glucose 4-epimerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.1.3.2 5.1.3.2] </span>
+or leave the SCENE parameter empty for the default display.
-|GENE=
+-->
-|DOMAIN=
+{{STRUCTURE_1a9y|  PDB=1a9y  |  SCENE=  }}
-|RELATEDENTRY=
-|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1a9y FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1a9y OCA], [http://www.ebi.ac.uk/pdbsum/1a9y PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1a9y RCSB]</span>
-}}
 '''UDP-GALACTOSE 4-EPIMERASE MUTANT S124A/Y149F COMPLEXED WITH UDP-GLUCOSE'''
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 [[Category: Holden, H M.]]
 [[Category: Thoden, J B.]]
-[[Category: dehydrogenase]]
+[[Category: Dehydrogenase]]
-[[Category: epimerase]]
+[[Category: Epimerase]]
-[[Category: galactose metabolism]]
+[[Category: Galactose metabolism]]
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May  2 10:01:46 2008''
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Mar 30 18:36:18 2008''