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| [[Image:1xys.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1xys| PDB=1xys | SCENE= }} | | {{STRUCTURE_1xys| PDB=1xys | SCENE= }} |
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| '''CATALYTIC CORE OF XYLANASE A E246C MUTANT'''
| | ===CATALYTIC CORE OF XYLANASE A E246C MUTANT=== |
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| ==Overview==
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| BACKGROUND: Sequence alignment suggests that xylanases evolved from two ancestral proteins and therefore can be grouped into two families, designated F and G. Family F enzymes show no sequence similarity with any known structure and their architecture is unknown. Studies of an inactive enzyme-substrate complex will help to elucidate the structural basis of binding and catalysis in the family F xylanases. RESULTS: We have therefore determined the crystal structure of the catalytic domain of a family F enzyme, Pseudomonas fluorescens subsp. cellulosa xylanase A, at 2.5 A resolution and a crystallographic R-factor of 0.20. The structure was solved using an engineered catalytic core in which the nucleophilic glutamate was replaced by a cysteine. As expected, this yielded both high-quality mercurial derivatives and an inactive enzyme which enabled the preparation of the inactive enzyme-substrate complex in the crystal. We show that family F xylanases are eight-fold alpha/beta-barrels (TIM barrels) with two active-site glutamates, one of which is the nucleophile and the other the acid-base. Xylopentaose binds to five subsites A-E with the cleaved bond between subsites D and E. Ca2+ binding, remote from the active-site glutamates, stabilizes the structure and may be involved in the binding of extended substrates. CONCLUSIONS: The architecture of P. fluorescens subsp. cellulosa has been determined crystallographically to be a commonly occurring enzyme fold, the eight-fold alpha/beta-barrel. Xylopentaose binds across the carboxy-terminal end of the alpha/beta-barrel in an active-site cleft which contains the two catalytic glutamates.
| | The line below this paragraph, {{ABSTRACT_PUBMED_7881909}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 7881909 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_7881909}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Family 10 of glycosyl-hydrolase]] | | [[Category: Family 10 of glycosyl-hydrolase]] |
| [[Category: Family f xylanase]] | | [[Category: Family f xylanase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 15:40:39 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 13:25:49 2008'' |
