1gkl: Difference between revisions

BACKGROUND: Degradation of the plant cell wall requires the synergistic, action of a consortium of predominantly modular enzymes. In Clostridiae, these biocatalysts are organized into a supramolecular assembly termed a, "cellulosome." This multienzyme complex possesses, in addition to its, well-described cellulolytic activity, an apparatus specific for xylan, degradation. Cinnamic acid esterases hydrolyze the ferulate groups, involved in the crosslinking of arabinoxylans to lignin and thus play a, key role in the degradation of the plant cell wall in addition to having, promising industrial and medical applications. RESULTS: We have cloned and, overexpressed the feruloyl esterase module from a 5 domain xylanase, Xyn10B from Clostridium thermocellum. The native structure at 1.6 A, resolution has been solved with selenomethionine multiple wavelength, anomalous dispersion and refined to a final R(free) of 17.8%. The, structure of a hydrolytically inactive mutant, S954A, in complex with the, reaction product ferulic acid has been refined at a resolution of 1.4 A, with an R(free) of 16.0%. CONCLUSIONS: The C. thermocellum Xyn10B ferulic, acid esterase displays the alpha/beta-hydrolase fold and possesses a, classical Ser-His-Asp catalytic triad. Ferulate esterases are, characterized by their specificity, and the active center reveals the, binding site for ferulic acid and related compounds. Ferulate binds in a, small surface depression that possesses specificity determinants for both, the methoxy and hydroxyl ring substituents of the substrate. There appears, to be a lack of specificity for the xylan backbone, which may reflect the, intrinsic chemical heterogeneity of the natural substrate.

1GKL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Clostridium_thermocellum Clostridium thermocellum] with CD, FER, GOL and ACY as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Endo-1,4-beta-xylanase Endo-1,4-beta-xylanase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.8 3.2.1.8] Structure known Active Site: FEA. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1GKL OCA].  

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