2rht
From Proteopedia
OCA (Talk | contribs)
(New page: 200px<br /><applet load="2rht" size="350" color="white" frame="true" align="right" spinBox="true" caption="2rht, resolution 1.700Å" /> '''Crystal Structure o...)
Next diff →
Revision as of 09:24, 23 January 2008
|
Crystal Structure of the S112A mutant of a C-C hydrolase, BphD from Burkholderia xenovorans LB400, in complex with 3-Cl HOPDA
Overview
The microbial degradation of polychlorinated biphenyls (PCBs) by the, biphenyl catabolic (Bph) pathway is limited in part by the pathway's, fourth enzyme, BphD. BphD catalyzes an unusual carbon-carbon bond, hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA), in, which the substrate is subject to histidine-mediated enol-keto, tautomerization prior to hydrolysis. Chlorinated HOPDAs such as 3-Cl HOPDA, inhibit BphD. Here we report that BphD preferentially hydrolyzed a series, of 3-substituted HOPDAs in the order H > F > Cl > Me, suggesting that, catalysis is affected by steric, not electronic, determinants. Transient, state kinetic studies performed using WT BphD and the hydrolysis-defective, S112A variant indicated that large 3-substituents inhibited, His-265-catalyzed tautomerization by 5 orders of magnitude. Structural, analyses of S112A:3-Cl HOPDA and S112A:3,10-diF HOPDA complexes revealed a, nonproductive binding mode in which the plane defined by the C atoms of, HOPDA's dienoate moiety is nearly orthogonal to that of the proposed keto, tautomer observed in the S112A:HOPDA complex. Moreover, in the 3-Cl HOPDA, complex, the 2-hydroxo group is moved by 3.6 A from its position near the, catalytic His-265 to hydrogen bond with Arg-190 and access of His-265 is, blocked by the 3-Cl substituent. Nonproductive binding may be stabilized, by interactions involving the 3-substituent with non-polar side chains., Solvent molecules have poor access to C6 in the S112A:3-Cl HOPDA, structure, more consistent with hydrolysis occurring via an acyl-enzyme, than a gem-diol intermediate. These results provide insight into, engineering BphD for PCB degradation.
About this Structure
2RHT is a Single protein structure of sequence from Burkholderia xenovorans with , and as ligands. Full crystallographic information is available from OCA.
Reference
The molecular basis for inhibition of BphD, a C-C bond hydrolase involved in polychlorinated biphenyls degradation: Large 3-substituents prevent tautomerization., Bhowmik S, Horsman GP, Bolin JT, Eltis LD, J Biol Chem. 2007 Oct 11;. PMID:17932031
Page seeded by OCA on Wed Jan 23 11:24:29 2008
