2xr8

Crystal structure of biphenyl dioxygenase from Burkholderia xenovorans LB400

spinqualitylabelsall models 2xr8, resolution 2.49Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2xr8 is a 24 chain structure with sequence from Burkholderia cepacia lb400. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: FE2, FES Activity: Biphenyl 2,3-dioxygenase, with EC number 1.14.12.18 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [BPHE_BURXL] The beta subunit may be responsible for the substrate specificity of the enzyme. Publication Abstract from PubMed The biphenyl dioxygenase of Burkholderia xenovorans LB400 is a multicomponent Rieske-type oxygenase (RO) that catalyzes the dihydroxylation of biphenyl and many polychlorinated biphenyls (PCBs). The structural bases for the substrate specificity of the enzyme's oxygenase component (BphAE(LB400)) are largely unknown. BphAE(p4), a variant previously obtained through directed evolution, transforms several chlorobiphenyls, including 2,6-dichlorobiphenyl, more efficiently than BphAE(LB400) yet differs from the parent oxygenase at only two positions: T335A/F336M. Herein, we compare the structure of BphAE(LB400) and BphAE(p4) and examine the biochemical properties of two BphAE(LB400) variants with single substitutions, T335A or F336M. Our data show that residue 336 contacts the biphenyl and influences the regiospecificity of the reaction, but does not enhance the enzyme's reactivity toward 2,6-dichlorobiphenyl. By contrast, residue 335 did not contact biphenyl, but contributed significantly to expansion of the enzyme's substrate range. Crystal structures indicate that Thr335 imposes constraints through hydrogen bonds and non-bonded contacts to the segment from Val320 to Gln322. These contacts are lost when Thr is replaced by Ala, relieving intramolecular constraints and allowing for significant movement of this segment during binding of 2,6-dichlorobiphenyl, increasing the space available to accommodate the doubly-ortho-chlorinated congener 2,6-dichlorobiphenyl. This study provides important insight about how ROs can expand substrate range through mutations that increase the plasticity and/or mobility of protein segments lining the catalytic cavity. Structural insight into the expanded PCB-degrading abilities of a biphenyl dioxygenase obtained by directed evolution.,Kumar P, Mohammadi M, Viger JF, Barriault D, Gomez-Gil L, Eltis LD, Bolin JT, Sylvestre M J Mol Biol. 2010 Nov 9. PMID:21073881 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Dioxygenase

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