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[[Image:1dyo.gif|left|200px]]<br /><applet load="1dyo" size="350" color="white" frame="true" align="right" spinBox="true"
caption="1dyo, resolution 2.1&Aring;" />
'''XYLAN-BINDING DOMAIN FROM CBM 22, FORMALLY X6B DOMAIN'''<br />


==Overview==
==Xylan-Binding Domain from CBM 22, formally x6b domain==
Organophosphorus acid anhydride (OP) nerve agents are potent inhibitors which rapidly phosphonylate acetylcholinesterase (AChE) and then may undergo an internal dealkylation reaction (called "aging") to produce an OP-enzyme conjugate that cannot be reactivated. To understand the basis for irreversible inhibition, we solved the structures of aged conjugates obtained by reaction of Torpedo californica AChE (TcAChE) with diisopropylphosphorofluoridate (DFP), O-isopropylmethylphosponofluoridate (sarin), or O-pinacolylmethylphosphonofluoridate (soman) by X-ray crystallography to 2.3, 2.6, or 2.2 A resolution, respectively. The highest positive difference density peak corresponded to the OP phosphorus and was located within covalent bonding distance of the active-site serine (S200) in each structure. The OP-oxygen atoms were within hydrogen-bonding distance of four potential donors from catalytic subsites of the enzyme, suggesting that electrostatic forces significantly stabilize the aged enzyme. The active sites of aged sarin- and soman-TcAChE were essentially identical and provided structural models for the negatively charged, tetrahedral intermediate that occurs during deacylation with the natural substrate, acetylcholine. Phosphorylation with DFP caused an unexpected movement in the main chain of a loop that includes residues F288 and F290 of the TcAChE acyl pocket. This is the first major conformational change reported in the active site of any AChE-ligand complex, and it offers a structural explanation for the substrate selectivity of AChE.
<StructureSection load='1dyo' size='340' side='right'caption='[[1dyo]], [[Resolution|resolution]] 2.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1dyo]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Acetivibrio_thermocellus Acetivibrio thermocellus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1DYO OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1DYO FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.1&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=MSE:SELENOMETHIONINE'>MSE</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1dyo FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1dyo OCA], [https://pdbe.org/1dyo PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1dyo RCSB], [https://www.ebi.ac.uk/pdbsum/1dyo PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1dyo ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/XYNY_ACETH XYNY_ACETH]
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/dy/1dyo_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1dyo ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Many polysaccharide-degrading enzymes display a modular structure in which a catalytic module is attached to one or more noncatalytic modules. Several xylanases contain a module of previously unknown function (termed "X6" modules) that had been implicated in thermostability. We have investigated the properties of two such "thermostabilizing" modules, X6a and X6b from the Clostridium thermocellumxylanase Xyn10B. These modules, expressed either as discrete entities or as their natural fusions with the catalytic module, were assayed, and their capacity to bind various carbohydrates and potentiate hydrolytic activity was determined. The data showed that X6b, but not X6a, increased the activity of the enzyme against insoluble xylan and bound specifically to xylooligosaccharides and various xylans. In contrast, X6a exhibited no affinity for soluble or insoluble forms of xylan. Isothermal titration calorimetry revealed that the ligand-binding site of X6b accommodates approximately four xylose residues. The protein exhibited K(d) values in the low micromolar range for xylotetraose, xylopentaose, and xylohexaose; 24 microM for xylotriose; and 50 microM for xylobiose. Negative DeltaH and DeltaS values indicate that the interaction of X6b with xylooligosaccharides and xylan is driven by enthalpic forces. The three-dimensional structure of X6b has been solved by X-ray crystallography to a resolution of 2.1 A. The protein is a beta-sandwich that presents a tryptophan and two tyrosine residues on the walls of a shallow cleft that is likely to be the xylan-binding site. In view of the structural and carbohydrate-binding properties of X6b, it is proposed that this and related modules be re-assigned as family 22 carbohydrate-binding modules.


==About this Structure==
The X6 "thermostabilizing" domains of xylanases are carbohydrate-binding modules: structure and biochemistry of the Clostridium thermocellum X6b domain.,Charnock SJ, Bolam DN, Turkenburg JP, Gilbert HJ, Ferreira LM, Davies GJ, Fontes CM Biochemistry. 2000 May 2;39(17):5013-21. PMID:10819965<ref>PMID:10819965</ref>
1DYO 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 <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1DYO OCA].


==Reference==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
Crystal structures of aged phosphonylated acetylcholinesterase: nerve agent reaction products at the atomic level., Millard CB, Kryger G, Ordentlich A, Greenblatt HM, Harel M, Raves ML, Segall Y, Barak D, Shafferman A, Silman I, Sussman JL, Biochemistry. 1999 Jun 1;38(22):7032-9. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=10353814 10353814]
</div>
[[Category: Clostridium thermocellum]]
<div class="pdbe-citations 1dyo" style="background-color:#fffaf0;"></div>
[[Category: Single protein]]
== References ==
[[Category: Charnock, S J.]]
<references/>
[[Category: Davies, G J.]]
__TOC__
[[Category: Fontes, C M.G A.]]
</StructureSection>
[[Category: Gilbert, H J.]]
[[Category: Acetivibrio thermocellus]]
[[Category: CA]]
[[Category: Large Structures]]
[[Category: carbohydrate-binding module]]
[[Category: Charnock SJ]]
[[Category: xylan-binding]]
[[Category: Davies GJ]]
[[Category: xylanase]]
[[Category: Fontes CMGA]]
 
[[Category: Gilbert HJ]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:21:57 2008''

Latest revision as of 02:54, 21 November 2024

Xylan-Binding Domain from CBM 22, formally x6b domainXylan-Binding Domain from CBM 22, formally x6b domain

Structural highlights

1dyo is a 2 chain structure with sequence from Acetivibrio thermocellus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:X-ray diffraction, Resolution 2.1Å
Ligands:,
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

XYNY_ACETH

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

Publication Abstract from PubMed

Many polysaccharide-degrading enzymes display a modular structure in which a catalytic module is attached to one or more noncatalytic modules. Several xylanases contain a module of previously unknown function (termed "X6" modules) that had been implicated in thermostability. We have investigated the properties of two such "thermostabilizing" modules, X6a and X6b from the Clostridium thermocellumxylanase Xyn10B. These modules, expressed either as discrete entities or as their natural fusions with the catalytic module, were assayed, and their capacity to bind various carbohydrates and potentiate hydrolytic activity was determined. The data showed that X6b, but not X6a, increased the activity of the enzyme against insoluble xylan and bound specifically to xylooligosaccharides and various xylans. In contrast, X6a exhibited no affinity for soluble or insoluble forms of xylan. Isothermal titration calorimetry revealed that the ligand-binding site of X6b accommodates approximately four xylose residues. The protein exhibited K(d) values in the low micromolar range for xylotetraose, xylopentaose, and xylohexaose; 24 microM for xylotriose; and 50 microM for xylobiose. Negative DeltaH and DeltaS values indicate that the interaction of X6b with xylooligosaccharides and xylan is driven by enthalpic forces. The three-dimensional structure of X6b has been solved by X-ray crystallography to a resolution of 2.1 A. The protein is a beta-sandwich that presents a tryptophan and two tyrosine residues on the walls of a shallow cleft that is likely to be the xylan-binding site. In view of the structural and carbohydrate-binding properties of X6b, it is proposed that this and related modules be re-assigned as family 22 carbohydrate-binding modules.

The X6 "thermostabilizing" domains of xylanases are carbohydrate-binding modules: structure and biochemistry of the Clostridium thermocellum X6b domain.,Charnock SJ, Bolam DN, Turkenburg JP, Gilbert HJ, Ferreira LM, Davies GJ, Fontes CM Biochemistry. 2000 May 2;39(17):5013-21. PMID:10819965[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

  1. ↑ Charnock SJ, Bolam DN, Turkenburg JP, Gilbert HJ, Ferreira LM, Davies GJ, Fontes CM. The X6 "thermostabilizing" domains of xylanases are carbohydrate-binding modules: structure and biochemistry of the Clostridium thermocellum X6b domain. Biochemistry. 2000 May 2;39(17):5013-21. PMID:10819965

1dyo, resolution 2.10Å

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