1dyo
From Proteopedia
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'''XYLAN-BINDING DOMAIN FROM CBM 22, FORMALLY X6B DOMAIN''' | '''XYLAN-BINDING DOMAIN FROM CBM 22, FORMALLY X6B DOMAIN''' | ||
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[[Category: Fontes, C M.G A.]] | [[Category: Fontes, C M.G A.]] | ||
[[Category: Gilbert, H J.]] | [[Category: Gilbert, H J.]] | ||
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| - | [[Category: | + | [[Category: Xylan-binding]] |
| - | [[Category: | + | [[Category: Xylanase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 14:26:26 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 11:26, 2 May 2008
XYLAN-BINDING DOMAIN FROM CBM 22, FORMALLY X6B DOMAIN
Overview
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.
About this Structure
1DYO is a Single protein structure of sequence from Clostridium thermocellum. Full crystallographic information is available from OCA.
Reference
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:10353814 Page seeded by OCA on Fri May 2 14:26:26 2008
