1cqs

<table><tr><td colspan='2'>[[1cqs]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/"bacillus_fluorescens_putidus"_flugge_1886 "bacillus fluorescens putidus" flugge 1886]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1CQS OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1CQS FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=EQU:EQUILENIN'>EQU</scene></td></tr>

<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1opy|1opy]]</td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Steroid_Delta-isomerase Steroid Delta-isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.3.1 5.3.3.1] </span></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=1cqs FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1cqs OCA], [http://pdbe.org/1cqs PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1cqs RCSB], [http://www.ebi.ac.uk/pdbsum/1cqs PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1cqs ProSAT]</span></td></tr>

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== Publication Abstract from PubMed ==

Delta 5-3-ketosteroid isomerase (KSI) catalyzes the allylic isomerization of Delta 5-3-ketosteroids at a rate approaching the diffusion limit by an intramolecular transfer of a proton. Despite the extensive studies on the catalytic mechanism, it still remains controversial whether the catalytic residue Asp-99 donates a hydrogen bond to the steroid or to Tyr-14. To clarify the role of Asp-99 in the catalysis, two single mutants of D99E and D99L and three double mutants of Y14F/D99E, Y14F/D99N, and Y14F/D99L have been prepared by site-directed mutagenesis. The D99E mutant whose side chain at position 99 is longer by an additional methylene group exhibits nearly the same kcat as the wild-type while the D99L mutant exhibits ca. 125-fold lower kcat than that of the wild-type. The mutations made at positions 14 and 99 exert synergistic or partially additive effect on kcat in the double mutants, which is inconsistent with the mechanism based on the hydrogen-bonded catalytic dyad, Asp-99 COOH...Tyr-14 OH...C3-O of the steroid. The crystal structure of D99E/D38N complexed with equilenin, an intermediate analogue, at 1.9 A resolution reveals that the distance between Tyr-14 O eta and Glu-99 O epsilon is ca. 4.2 A, which is beyond the range for a hydrogen bond, and that the distance between Glu-99 O epsilon and C3-O of the steroid is maintained to be ca. 2.4 A, short enough for a hydrogen bond to be formed. Taken together, these results strongly support the idea that Asp-99 contributes to the catalysis by donating a hydrogen bond directly to the intermediate.

Asp-99 donates a hydrogen bond not to Tyr-14 but to the steroid directly in the catalytic mechanism of Delta 5-3-ketosteroid isomerase from Pseudomonas putida biotype B.,Choi G, Ha NC, Kim SW, Kim DH, Park S, Oh BH, Choi KY Biochemistry. 2000 Feb 8;39(5):903-9. PMID:10653633<ref>PMID:10653633</ref>

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

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<div class="pdbe-citations 1cqs" style="background-color:#fffaf0;"></div>

== References ==

<references/>

[[Category: Bacillus fluorescens putidus flugge 1886]]

[[Category: Steroid Delta-isomerase]]

[[Category: Choi, G]]

[[Category: Choi, K Y]]

[[Category: Ha, N C]]

[[Category: Kim, D H]]

[[Category: Kim, S W]]

[[Category: Oh, B H]]

[[Category: Park, S]]

[[Category: Putida lbhb]]