1e5n
From Proteopedia
(New page: 200px<br /><applet load="1e5n" size="450" color="white" frame="true" align="right" spinBox="true" caption="1e5n, resolution 3.2Å" /> '''E246C MUTANT OF P FLU...) |
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| - | [[Image:1e5n.jpg|left|200px]]<br /><applet load="1e5n" size=" | + | [[Image:1e5n.jpg|left|200px]]<br /><applet load="1e5n" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1e5n, resolution 3.2Å" /> | caption="1e5n, resolution 3.2Å" /> | ||
'''E246C MUTANT OF P FLUORESCENS SUBSP. CELLULOSA XYLANASE A IN COMPLEX WITH XYLOPENTAOSE'''<br /> | '''E246C MUTANT OF P FLUORESCENS SUBSP. CELLULOSA XYLANASE A IN COMPLEX WITH XYLOPENTAOSE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The structure of the complex between a catalytically compromised family 10 | + | The structure of the complex between a catalytically compromised family 10 xylanase and a xylopentaose substrate has been determined by X-ray crystallography and refined to 3.2 A resolution. The substrate binds at the C-terminal end of the eightfold betaalpha-barrel of Pseudomonas fluorescens subsp. cellulosa xylanase A and occupies substrate binding subsites -1 to +4. Crystal contacts are shown to prevent the expected mode of binding from subsite -2 to +3, because of steric hindrance to subsite -2. The loss of accessible surface at individual subsites on binding of xylopentaose parallels well previously reported experimental measurements of individual subsites binding energies, decreasing going from subsite +2 to +4. Nine conserved residues contribute to subsite -1, including three tryptophan residues forming an aromatic cage around the xylosyl residue at this subsite. One of these, Trp 313, is the single residue contributing most lost accessible surface to subsite -1, and goes from a highly mobile to a well-defined conformation on binding of the substrate. A comparison of xylanase A with C. fimi CEX around the +1 subsite suggests that a flatter and less polar surface is responsible for the better catalytic properties of CEX on aryl substrates. The view of catalysis that emerges from combining this with previously published work is the following: (1) xylan is recognized and bound by the xylanase as a left-handed threefold helix; (2) the xylosyl residue at subsite -1 is distorted and pulled down toward the catalytic residues, and the glycosidic bond is strained and broken to form the enzyme-substrate covalent intermediate; (3) the intermediate is attacked by an activated water molecule, following the classic retaining glycosyl hydrolase mechanism. |
==About this Structure== | ==About this Structure== | ||
| - | 1E5N is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_fluorescens Pseudomonas fluorescens] with CA as [http://en.wikipedia.org/wiki/ligand ligand]. 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] Full crystallographic information is available from [http:// | + | 1E5N is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_fluorescens Pseudomonas fluorescens] with <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. 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] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1E5N OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Pseudomonas fluorescens]] | [[Category: Pseudomonas fluorescens]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Harris, G | + | [[Category: Harris, G W.]] |
| - | [[Category: Jenkins, J | + | [[Category: Jenkins, J A.]] |
| - | [[Category: Leggio, L | + | [[Category: Leggio, L Lo.]] |
| - | [[Category: Pickersgill, R | + | [[Category: Pickersgill, R W.]] |
[[Category: CA]] | [[Category: CA]] | ||
[[Category: family 10]] | [[Category: family 10]] | ||
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[[Category: xylan degradation]] | [[Category: xylan degradation]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:24:06 2008'' |
Revision as of 10:24, 21 February 2008
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E246C MUTANT OF P FLUORESCENS SUBSP. CELLULOSA XYLANASE A IN COMPLEX WITH XYLOPENTAOSE
Overview
The structure of the complex between a catalytically compromised family 10 xylanase and a xylopentaose substrate has been determined by X-ray crystallography and refined to 3.2 A resolution. The substrate binds at the C-terminal end of the eightfold betaalpha-barrel of Pseudomonas fluorescens subsp. cellulosa xylanase A and occupies substrate binding subsites -1 to +4. Crystal contacts are shown to prevent the expected mode of binding from subsite -2 to +3, because of steric hindrance to subsite -2. The loss of accessible surface at individual subsites on binding of xylopentaose parallels well previously reported experimental measurements of individual subsites binding energies, decreasing going from subsite +2 to +4. Nine conserved residues contribute to subsite -1, including three tryptophan residues forming an aromatic cage around the xylosyl residue at this subsite. One of these, Trp 313, is the single residue contributing most lost accessible surface to subsite -1, and goes from a highly mobile to a well-defined conformation on binding of the substrate. A comparison of xylanase A with C. fimi CEX around the +1 subsite suggests that a flatter and less polar surface is responsible for the better catalytic properties of CEX on aryl substrates. The view of catalysis that emerges from combining this with previously published work is the following: (1) xylan is recognized and bound by the xylanase as a left-handed threefold helix; (2) the xylosyl residue at subsite -1 is distorted and pulled down toward the catalytic residues, and the glycosidic bond is strained and broken to form the enzyme-substrate covalent intermediate; (3) the intermediate is attacked by an activated water molecule, following the classic retaining glycosyl hydrolase mechanism.
About this Structure
1E5N is a Single protein structure of sequence from Pseudomonas fluorescens with as ligand. Active as Endo-1,4-beta-xylanase, with EC number 3.2.1.8 Full crystallographic information is available from OCA.
Reference
X-ray crystallographic study of xylopentaose binding to Pseudomonas fluorescens xylanase A., Leggio LL, Jenkins J, Harris GW, Pickersgill RW, Proteins. 2000 Nov 15;41(3):362-73. PMID:11025547
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