1kvs

[[Image:1kvs.gif|left|200px]]

|PDB= 1kvs |SIZE=350|CAPTION= <scene name='initialview01'>1kvs</scene>, resolution 2.15&Aring;

|SITE=

|LIGAND= <scene name='pdbligand=NA:SODIUM+ION'>NA</scene>, <scene name='pdbligand=NAD:NICOTINAMIDE-ADENINE-DINUCLEOTIDE'>NAD</scene>, <scene name='pdbligand=PEG:DI(HYDROXYETHYL)ETHER'>PEG</scene>, <scene name='pdbligand=UPG:URIDINE-5&#39;-DIPHOSPHATE-GLUCOSE'>UPG</scene>

|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>

|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1kvs FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1kvs OCA], [http://www.ebi.ac.uk/pdbsum/1kvs PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1kvs RCSB]</span>

 

 

==Overview==

UDP-galactose 4-epimerase plays a critical role in sugar metabolism by catalyzing the interconversion of UDP-galactose and UDP-glucose. Originally, it was assumed that the enzyme contained a "traditional" catalytic base that served to abstract a proton from the 4'-hydroxyl group of the UDP-glucose or UDP-galactose substrates during the course of the reaction. However, recent high-resolution X-ray crystallographic analyses of the protein from Escherichia coli have demonstrated the lack of an aspartate, a glutamate, or a histidine residue properly oriented within the active site cleft for serving such a functional role. Rather, the X-ray crystallographic investigation of the epimerase.NADH.UDP-glucose abortive complex from this laboratory has shown that both Ser 124 and Tyr 149 are located within hydrogen bonding distance to the 4'- and 3'-hydroxyl groups of the sugar, respectively. To test the structural role of Ser 124 in the reaction mechanism of epimerase, three site-directed mutant proteins, namely S124A, S124T, and S124V, were constructed and crystals of the S124A.NADH.UDP, S124A.NADH.UDP-glucose, S124T. NADH.UDP-glucose, and S124V.NADH.UDP-glucose complexes were grown. All of the crystals employed in this investigation belonged to the space group P3221 with the following unit cell dimensions: a = b = 83.8 A, c = 108.4 A, and one subunit per asymmetric unit. X-ray data sets were collected to at least 2.15 A resolution, and each protein model was subsequently refined to an R value of lower than 19.0% for all measured X-ray data. The investigations described here demonstrate that the decreases in enzymatic activities observed for these mutant proteins are due to the loss of a properly positioned hydroxyl group at position 124 and not to major tertiary and quaternary structural perturbations. In addition, these structures demonstrate the importance of a hydroxyl group at position 124 in stabilizing the anti conformation of the nicotinamide ring as observed in the previous structural analysis of the epimerase.NADH. UDP complex.

 

1KVS is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KVS OCA].

 

Molecular structures of the S124A, S124T, and S124V site-directed mutants of UDP-galactose 4-epimerase from Escherichia coli., Thoden JB, Gulick AM, Holden HM, Biochemistry. 1997 Sep 2;36(35):10685-95. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/9271499 9271499]

[[Category: Single protein]]

[[Category: UDP-glucose 4-epimerase]]

[[Category: Gulick, A.]]

[[Category: Holden, H M.]]

[[Category: Thoden, J B.]]