3cox: Difference between revisions

[[Image:3cox.gif|left|200px]]<br /><applet load="3cox" size="350" color="white" frame="true" align="right" spinBox="true"  

Cholesterol oxidase from Brevibacterium sterolicum is a flavin-dependent enzyme that catalyzes the oxidation and isomerization of 3 beta-hydroxy steroids with a double bond at delta 5-delta 6 of the steroid ring backbone. The crystal structure of the free enzyme in the absence of a steroid substrate has previously been determined. In this paper we report the crystal structure of the complex of cholesterol oxidase with the steroid substrate dehydroisoandrosterone, refined at 1.8-A resolution. The final crystallographic R-value is 15.7% for all reflections between 10.0- and 1.8-A resolution. The steroid is buried within the protein in an internal cavity which, in the free enzyme crystal structure, was occupied by a lattice of water molecules. The conformations of a number of side chains lining the active-site cavity have changed in order to accommodate the steroid substrate. A loop region of the structure between residues 70 and 90 differs significantly between the substrate-free and substrate-bound forms of the enzyme, presumably to facilitate binding of the steroid. The hydroxyl group of the steroid substrate is hydrogen-bonded to both the flavin ring system of the FAD cofactor and a bound water molecule. FAD-dependent cholesterol oxidase shares significant structural homology with another flavoenzyme, glucose oxidase, suggesting that it might also be a member of the glucose-methanol-choline (GMC) oxidoreductase family. Although there is only limited sequence homology, a superposition of these two structures reveals a conserved histidine residue within hydrogen-bonding distance of the active-site water molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

3COX is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Brevibacterium_sterolicum Brevibacterium sterolicum] with <scene name='pdbligand=FAD:'>FAD</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure supersedes the now removed PDB entry 1COX. Active as [http://en.wikipedia.org/wiki/Cholesterol_oxidase Cholesterol oxidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.1.3.6 1.1.3.6] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3COX OCA].  

[[Category: Blow, D M.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 19:08:49 2008''