1db3

[[Image:1db3.gif|left|200px]]

|PDB= 1db3 |SIZE=350|CAPTION= <scene name='initialview01'>1db3</scene>, resolution 2.3&Aring;

|SITE=

|LIGAND=

|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/GDP-mannose_4,6-dehydratase GDP-mannose 4,6-dehydratase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.1.47 4.2.1.47] </span>

|GENE=

|DOMAIN=

|RELATEDENTRY=

|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1db3 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1db3 OCA], [http://www.ebi.ac.uk/pdbsum/1db3 PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1db3 RCSB]</span>

 

 

 

==Overview==

Background: GDP-mannose 4,6 dehydratase (GMD) catalyzes the conversion of GDP-(D)-mannose to GDP-4-keto, 6-deoxy-(D)-mannose. This is the first and regulatory step in the de novo biosynthesis of GDP-(L)-fucose. Fucose forms part of a number of glycoconjugates, including the ABO blood groups and the selectin ligand sialyl Lewis X. Defects in GDP-fucose metabolism have been linked to leukocyte adhesion deficiency type II (LADII). Results: The structure of the GDP-mannose 4,6 dehydratase apo enzyme has been determined and refined using data to 2.3 A resolution. GMD is a homodimeric protein with each monomer composed of two domains. The larger N-terminal domain binds the NADP(H) cofactor in a classical Rossmann fold and the C-terminal domain harbors the sugar-nucleotide binding site. We have determined the GMD dissociation constants for NADP, NADPH and GDP-mannose. Each GMD monomer binds one cofactor and one substrate molecule, suggesting that both subunits are catalytically competent. GDP-fucose acts as a competitive inhibitor, suggesting that it binds to the same site as GDP-mannose, providing a mechanism for the feedback inhibition of fucose biosynthesis. Conclusions: The X-ray structure of GMD reveals that it is a member of the short-chain dehydrogenase/reductase (SDR) family of proteins. We have modeled the binding of NADP and GDP-mannose to the enzyme and mutated four of the active-site residues to determine their function. The combined modeling and mutagenesis data suggests that at position 133 threonine substitutes serine as part of the serine-tyrosine-lysine catalytic triad common to the SDR family and Glu 135 functions as an active-site base.

 

==About this Structure==

1DB3 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=1DB3 OCA].

 

Structural and kinetic analysis of Escherichia coli GDP-mannose 4,6 dehydratase provides insights into the enzyme's catalytic mechanism and regulation by GDP-fucose., Somoza JR, Menon S, Schmidt H, Joseph-McCarthy D, Dessen A, Stahl ML, Somers WS, Sullivan FX, Structure. 2000 Feb 15;8(2):123-35. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/10673432 10673432]

[[Category: GDP-mannose 4,6-dehydratase]]

[[Category: Single protein]]

[[Category: Menon, S.]]

[[Category: Somers, W S.]]

[[Category: Somoza, J R.]]

[[Category: Sullivan, F X.]]