1z9a

<StructureSection load='1z9a' size='340' side='right' caption='[[1z9a]], [[Resolution|resolution]] 2.40&Aring;' scene=''>

<table><tr><td colspan='2'>[[1z9a]] is a 4 chain structure with sequence from [http://en.wikipedia.org/wiki/Candida_tenuis Candida tenuis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1Z9A OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1Z9A FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=NAD:NICOTINAMIDE-ADENINE-DINUCLEOTIDE'>NAD</scene></td></tr>

<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">XYL1, XYLR ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=45596 Candida tenuis])</td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1z9a FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1z9a OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1z9a RCSB], [http://www.ebi.ac.uk/pdbsum/1z9a PDBsum]</span></td></tr>

[[http://www.uniprot.org/uniprot/XYL1_CANTE XYL1_CANTE]] Reduces D-xylose into xylitol. Has a preference for NADPH, but can also utilize NADH as cosubstrate.

<scriptWhenChecked>select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/z9/1z9a_consurf.spt"</scriptWhenChecked>

</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/chain_selection.php?pdb_ID=2ata ConSurf].

<div style="background-color:#fffaf0;">

== Publication Abstract from PubMed ==

Little is known about how substrates bind to CtXR (Candida tenuis xylose reductase; AKR2B5) and other members of the AKR (aldo-keto reductase) protein superfamily. Modelling of xylose into the active site of CtXR suggested that Trp23, Asp50 and Asn309 are the main components of pentose-specific substrate-binding recognition. Kinetic consequences of site-directed substitutions of these residues are reported. The mutants W23F and W23Y catalysed NADH-dependent reduction of xylose with only 4 and 1% of the wild-type efficiency (kcat/K(m)) respectively, but improved the wild-type selectivity for utilization of ketones, relative to xylose, by factors of 156 and 471 respectively. Comparison of multiple sequence alignment with reported specificities of AKR members emphasizes a conserved role of Trp23 in determining aldehyde-versus-ketone substrate selectivity. D50A showed 31 and 18% of the wild-type catalytic-centre activities for xylose reduction and xylitol oxidation respectively, consistent with a decrease in the rates of the chemical steps caused by the mutation, but no change in the apparent substrate binding constants and the pattern of substrate specificities. The 30-fold preference of the wild-type for D-galactose compared with 2-deoxy-D-galactose was lost completely in N309A and N309D mutants. Comparison of the 2.4 A (1 A=0.1 nm) X-ray crystal structure of mutant N309D bound to NAD+ with the previous structure of the wild-type holoenzyme reveals no major structural perturbations. The results suggest that replacement of Asn309 with alanine or aspartic acid disrupts the function of the original side chain in donating a hydrogen atom for bonding with the substrate C-2(R) hydroxy group, thus causing a loss of transition-state stabilization energy of 8-9 kJ/mol.

Probing the substrate binding site of Candida tenuis xylose reductase (AKR2B5) with site-directed mutagenesis.,Kratzer R, Leitgeb S, Wilson DK, Nidetzky B Biochem J. 2006 Jan 1;393(Pt 1):51-8. PMID:16336198<ref>PMID:16336198</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Candida tenuis]]

[[Category: Kratzer, R]]

[[Category: Leitgeb, S]]

[[Category: Nidetzky, B]]

[[Category: Wilson, D K]]

[[Category: Xylose reductase]]