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| {{STRUCTURE_1g66| PDB=1g66 | SCENE= }} | | {{STRUCTURE_1g66| PDB=1g66 | SCENE= }} |
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| '''ACETYLXYLAN ESTERASE AT 0.90 ANGSTROM RESOLUTION'''
| | ===ACETYLXYLAN ESTERASE AT 0.90 ANGSTROM RESOLUTION=== |
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| ==Overview==
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| Acetylxylan esterase (AXEII; 207 amino acids) from Penicillium purpurogenum has substrate specificities toward acetate esters of d-xylopyranose residues in xylan and belongs to a new class of alpha/beta hydrolases. The crystal structure of AXEII has been determined by single isomorphous replacement and anomalous scattering, and refined at 0.90- and 1.10-A resolutions with data collected at 85 K and 295 K, respectively. The tertiary structure consists of a doubly wound alpha/beta sandwich, having a central six-stranded parallel beta-sheet flanked by two parallel alpha-helices on each side. The catalytic residues Ser(90), His(187), and Asp(175) are located at the C-terminal end of the sheet, an exposed region of the molecule. The serine and histidine side chains in the 295 K structure show the frequently observed conformations in which Ser(90) is trans and the hydroxyl group is in the plane of the imidazole ring of His(187). However, the structure at 85 K displays an additional conformation in which Ser(90) side-chain hydroxyl is away from the plane of the imidazole ring of His(187). The His(187) side chain forms a hydrogen bond with a sulfate ion and adopts an altered conformation. The only other known hydrolase that has a similar tertiary structure is Fusarium solani cutinase. The exposed nature of the catalytic triad suggests that AXEII is a pure esterase, i.e. an alpha/beta hydrolase with specificity for nonlipidic polar substrates.
| | The line below this paragraph, {{ABSTRACT_PUBMED_11134051}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11134051 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11134051}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Ultra-high resolution]] | | [[Category: Ultra-high resolution]] |
| [[Category: Xylan]] | | [[Category: Xylan]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 17:11:16 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 04:35:17 2008'' |
