View source for 1wcq

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

 {{Structure
|PDB= 1wcq |SIZE=350|CAPTION= <scene name='initialview01'>1wcq</scene>, resolution 2.10&Aring;
|SITE= <scene name='pdbsite=AC1:Dan+Binding+Site+For+Chain+C'>AC1</scene>
|LIGAND= <scene name='pdbligand=DAN:2-DEOXY-2,3-DEHYDRO-N-ACETYL-NEURAMINIC+ACID'>DAN</scene>, <scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=NA:SODIUM+ION'>NA</scene>
|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Exo-alpha-sialidase Exo-alpha-sialidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.18 3.2.1.18] </span>
|GENE= 
|DOMAIN=
|RELATEDENTRY=
|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1wcq FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1wcq OCA], [http://www.ebi.ac.uk/pdbsum/1wcq PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1wcq RCSB]</span>
}}

'''MUTAGENESIS OF THE NUCLEOPHILIC TYROSINE IN A BACTERIAL SIALIDASE TO PHENYLALANINE.'''


==Overview==
Mutants of the Micromonospora viridifaciens sialidase, Y370E and Y370F, are catalytically active retaining enzymes that operate by different mechanisms. Previous substitutions with smaller amino acids, including Y370D, yielded inverting sialidases. At least one water molecule can fit into the active-site cavity of this mutant and act as a nucleophile from the face opposite the leaving group (Biochemistry 2003, 42, 12 682). Thus, addition of a CH(2) unit (Asp versus Glu) changes the mechanism from inversion back to retention of configuration. Based on Bronsted beta(lg) values, it is proposed that the Y370E mutant reacts by a double-displacement mechanism (beta(lg) on k(cat)/K(m) -0.36+/-0.04) with Glu370 acting as the nucleophile. However, the Y370F mutant (beta(lg) on k(cat)/K(m) -0.79+/-0.12) reacts via a dissociative transition state. The crystal structure of the Y370F mutant complexed with 2-deoxy-2,3-dehydro-N-acetylneuraminic acid shows no significant active-site perturbation relative to the wild-type enzyme.

==About this Structure==
1WCQ is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Micromonospora_viridifaciens Micromonospora viridifaciens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1WCQ OCA]. 

==Reference==
Two nucleophilic mutants of the Micromonospora viridifaciens sialidase operate with retention of configuration by two different mechanisms., Watson JN, Newstead S, Narine AA, Taylor G, Bennet AJ, Chembiochem. 2005 Nov;6(11):1999-2004. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/16206228 16206228]
[[Category: Exo-alpha-sialidase]]
[[Category: Micromonospora viridifaciens]]
[[Category: Single protein]]
[[Category: Bennet, A J.]]
[[Category: Newstead, S.]]
[[Category: Taylor, G.]]
[[Category: Watson, J N.]]
[[Category: glycosidase]]
[[Category: hydrolase neuraminidase]]
[[Category: micromonospora viridifacien]]
[[Category: sialidase]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Mar 31 00:34:27 2008''