5a8d

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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The truncated carbohydrate-active enzyme belonging to family 43 glycoside hydrolase from Clostridium thermocellum (CtGH43) is an alpha-L-arabinofuranosidase that in combination with endoxylanase leads to complete breakdown of L-arabinosyl-substituted xylans. The recombinant enzyme CtGH43 from C. thermocellum was overexpressed in Escherichia coli and purified by immobilized metal-ion affinity chromatography. The recombinant CtGH43 has a molecular mass of 35.86 kDa. Preliminary structural characterization was carried out on CtGH43 crystallized from different conditions, which gave either cube-shaped or brick-shaped crystals. These diffracted to a resolution of 1.65 A for the cubic form and 1.1 A for the monoclinic form. Molecular replacement was used to solve the CtGH43 structure.
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The recent division of the large glycoside hydrolase family 43 (GH43) into subfamilies offers a renewed opportunity to develop structure-function studies aimed at clarifying the molecular determinants of substrate specificity in carbohydrate-degrading enzymes. alpha-L-Arabinofuranosidases (EC 3.2.1.55) remove arabinose side chains from heteropolysaccharides such as xylan and arabinan. However, there is some evidence suggesting that arabinofuranosidases are substrate-specific, being unable to display a debranching activity on different polysaccharides. Here, the structure of Clostridium thermocellum arabinofuranosidase 43A (CtAbf43A), which has been shown to act in the removal of arabinose side chains from arabinoxylan but not from pectic arabinan, is reported. CtAbf43A belongs to GH43 subfamily 16, the members of which have a restricted capacity to attack xylans. The crystal structure of CtAbf43A comprises a five-bladed beta-propeller fold typical of GH43 enzymes. CtAbf43A displays a highly compact architecture compatible with its high thermostability. Analysis of CtAbf43A along with the other member of GH43 subfamily 16 with known structure, the Bacillus subtilis arabinofuranosidase BsAXH-m2,3, suggests that the specificity of subfamily 16 for arabinoxylan is conferred by a long surface substrate-binding cleft that is complementary to the xylan backbone. The lack of a curved-shaped carbohydrate-interacting platform precludes GH43 subfamily 16 enzymes from interacting with the nonlinear arabinan scaffold and therefore from deconstructing this polysaccharide.
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Crystallization and preliminary X-ray crystallographic analysis of a novel alpha-L-arabinofuranosidase (CtGH43) from Clostridium thermocellum ATCC 27405.,Goyal A, Ahmed S, Fontes CM, Najmudin S Acta Crystallogr F Struct Biol Commun. 2014 May;70(Pt 5):616-8. doi:, 10.1107/S2053230X14006402. Epub 2014 Apr 15. PMID:24817722<ref>PMID:24817722</ref>
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Molecular determinants of substrate specificity revealed by the structure of Clostridium thermocellum arabinofuranosidase 43A from glycosyl hydrolase family 43 subfamily 16.,Goyal A, Ahmed S, Sharma K, Gupta V, Bule P, Alves VD, Fontes CM, Najmudin S Acta Crystallogr D Struct Biol. 2016 Dec 1;72(Pt 12):1281-1289. Epub 2016 Nov 29. PMID:27917828<ref>PMID:27917828</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 06:55, 9 March 2017

The high resolution structure of a novel alpha-L-arabinofuranosidase (CtGH43) from Clostridium thermocellum ATCC 27405

5a8d, resolution 1.65Å

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