2c0q: Difference between revisions
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==Overview== | ==Overview== | ||
Organophosphorus compounds (OPs) interfere with the catalytic mechanism of, acetylcholinesterase (AChE) by rapidly phosphorylating the catalytic, serine residue. The inhibited enzyme can at least partly be reactivated, with nucleophilic reactivators such as oximes. The covalently attached OP, conjugate may undergo further intramolecular dealkylation or deamidation, reactions, a process termed "aging" that results in an enzyme considered, completely resistant to reactivation. Of particular interest is the, inhibition and aging reaction of the OP compound tabun since tabun, conjugates display an extraordinary resistance toward most reactivators of, today. To investigate the structural basis for this resistance, we, determined the crystal structures of Mus musculus AChE (mAChE) inhibited, by ... | Organophosphorus compounds (OPs) interfere with the catalytic mechanism of, acetylcholinesterase (AChE) by rapidly phosphorylating the catalytic, serine residue. The inhibited enzyme can at least partly be reactivated, with nucleophilic reactivators such as oximes. The covalently attached OP, conjugate may undergo further intramolecular dealkylation or deamidation, reactions, a process termed "aging" that results in an enzyme considered, completely resistant to reactivation. Of particular interest is the, inhibition and aging reaction of the OP compound tabun since tabun, conjugates display an extraordinary resistance toward most reactivators of, today. To investigate the structural basis for this resistance, we, determined the crystal structures of Mus musculus AChE (mAChE) inhibited, by tabun prior to and after the aging reaction. The nonaged tabun, conjugate induces a structural change of the side chain of His447 that, uncouples the catalytic triad and positions the imidazole ring of His447, in a conformation where it may form a hydrogen bond to a water molecule., Moreover, an unexpected displacement of the side chain of Phe338 narrows, the active site gorge. In the crystal structure of the aged tabun, conjugate, the side chains of His447 and Phe338 are reversed to the, conformation found in the apo structure of mAChE. A hydrogen bond between, the imidazole ring of His447 and the ethoxy oxygen of the aged tabun, conjugate stabilizes the side chain of His447. The displacement of the, side chain of Phe338 into the active site gorge of the nonaged tabun, conjugate may interfere with the accessibility of reactivators and thereby, contribute to the high resistance of tabun conjugates toward reactivation. | ||
==About this Structure== | ==About this Structure== | ||
2C0Q is a | 2C0Q is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mus_musculus Mus musculus] with NTJ and P6G as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Acetylcholinesterase Acetylcholinesterase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.1.7 3.1.1.7] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2C0Q OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: serine esterase]] | [[Category: serine esterase]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 5 14:16:21 2007'' | ||
Revision as of 15:11, 5 November 2007
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NON-AGED FORM OF MOUSE ACETYLCHOLINESTERASE INHIBITED BY TABUN
OverviewOverview
Organophosphorus compounds (OPs) interfere with the catalytic mechanism of, acetylcholinesterase (AChE) by rapidly phosphorylating the catalytic, serine residue. The inhibited enzyme can at least partly be reactivated, with nucleophilic reactivators such as oximes. The covalently attached OP, conjugate may undergo further intramolecular dealkylation or deamidation, reactions, a process termed "aging" that results in an enzyme considered, completely resistant to reactivation. Of particular interest is the, inhibition and aging reaction of the OP compound tabun since tabun, conjugates display an extraordinary resistance toward most reactivators of, today. To investigate the structural basis for this resistance, we, determined the crystal structures of Mus musculus AChE (mAChE) inhibited, by tabun prior to and after the aging reaction. The nonaged tabun, conjugate induces a structural change of the side chain of His447 that, uncouples the catalytic triad and positions the imidazole ring of His447, in a conformation where it may form a hydrogen bond to a water molecule., Moreover, an unexpected displacement of the side chain of Phe338 narrows, the active site gorge. In the crystal structure of the aged tabun, conjugate, the side chains of His447 and Phe338 are reversed to the, conformation found in the apo structure of mAChE. A hydrogen bond between, the imidazole ring of His447 and the ethoxy oxygen of the aged tabun, conjugate stabilizes the side chain of His447. The displacement of the, side chain of Phe338 into the active site gorge of the nonaged tabun, conjugate may interfere with the accessibility of reactivators and thereby, contribute to the high resistance of tabun conjugates toward reactivation.
About this StructureAbout this Structure
2C0Q is a Single protein structure of sequence from Mus musculus with NTJ and P6G as ligands. Active as Acetylcholinesterase, with EC number 3.1.1.7 Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Structural changes of phenylalanine 338 and histidine 447 revealed by the crystal structures of tabun-inhibited murine acetylcholinesterase., Ekstrom F, Akfur C, Tunemalm AK, Lundberg S, Biochemistry. 2006 Jan 10;45(1):74-81. PMID:16388582
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