2r1m
From Proteopedia
(New page: 200px<br /><applet load="2r1m" size="350" color="white" frame="true" align="right" spinBox="true" caption="2r1m, resolution 2.50Å" /> '''OpdA from Agrobacter...) |
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==Overview== | ==Overview== | ||
| - | The mechanism by which the binuclear metallophosphotriesterases (PTEs, E.C. 3.1.8.1) catalyse substrate hydrolysis has been extensively studied. | + | The mechanism by which the binuclear metallophosphotriesterases (PTEs, E.C. 3.1.8.1) catalyse substrate hydrolysis has been extensively studied. The mu-hydroxo bridge between the metal ions has been proposed to be the initiating nucleophile in the hydrolytic reaction. In contrast, analysis of some biomimetic systems has indicated that mu-hydroxo bridges are often not themselves nucleophiles, but act as general bases for freely exchangeable nucleophilic water molecules. Herein, we present crystallographic analyses of a bacterial PTE from Agrobacterium radiobacter, OpdA, capturing the enzyme-substrate complex during hydrolysis. This model of the Michaelis complex suggests the alignment of the substrate will favour attack from a solvent molecule terminally coordinated to the alpha-metal ion. The bridging of both metal ions by the product, without disruption of the mu-hydroxo bridge, is also consistent with nucleophilic attack occurring from the terminal position. When phosphodiesters are soaked into crystals of OpdA, they coordinate bidentately to the beta-metal ion, displacing the mu-hydroxo bridge. Thus, alternative product-binding modes exist for the PTEs, and it is the bridging mode that appears to result from phosphotriester hydrolysis. Kinetic analysis of the PTE and promiscuous phosphodiesterase activities confirms that the presence of a mu-hydroxo bridge during phosphotriester hydrolysis is correlated with a lower pK(a) for the nucleophile, consistent with a general base function during catalysis. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Aryldialkylphosphatase]] | [[Category: Aryldialkylphosphatase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Carr, P | + | [[Category: Carr, P D.]] |
| - | [[Category: Foo, J | + | [[Category: Foo, J L.]] |
| - | [[Category: Jackson, C | + | [[Category: Jackson, C J.]] |
| - | [[Category: Kim, H | + | [[Category: Kim, H K.]] |
| - | [[Category: Liu, J | + | [[Category: Liu, J W.]] |
| - | [[Category: Ollis, D | + | [[Category: Ollis, D L.]] |
[[Category: Salem, G.]] | [[Category: Salem, G.]] | ||
[[Category: CO]] | [[Category: CO]] | ||
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[[Category: phosphotriesterase]] | [[Category: phosphotriesterase]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 18:43:56 2008'' |
Revision as of 16:44, 21 February 2008
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OpdA from Agrobacterium radiobacter with bound product diethyl phosphate from crystal soaking with diethyl 4-methoxyphenyl phosphate (450h)- 2.5 A
Overview
The mechanism by which the binuclear metallophosphotriesterases (PTEs, E.C. 3.1.8.1) catalyse substrate hydrolysis has been extensively studied. The mu-hydroxo bridge between the metal ions has been proposed to be the initiating nucleophile in the hydrolytic reaction. In contrast, analysis of some biomimetic systems has indicated that mu-hydroxo bridges are often not themselves nucleophiles, but act as general bases for freely exchangeable nucleophilic water molecules. Herein, we present crystallographic analyses of a bacterial PTE from Agrobacterium radiobacter, OpdA, capturing the enzyme-substrate complex during hydrolysis. This model of the Michaelis complex suggests the alignment of the substrate will favour attack from a solvent molecule terminally coordinated to the alpha-metal ion. The bridging of both metal ions by the product, without disruption of the mu-hydroxo bridge, is also consistent with nucleophilic attack occurring from the terminal position. When phosphodiesters are soaked into crystals of OpdA, they coordinate bidentately to the beta-metal ion, displacing the mu-hydroxo bridge. Thus, alternative product-binding modes exist for the PTEs, and it is the bridging mode that appears to result from phosphotriester hydrolysis. Kinetic analysis of the PTE and promiscuous phosphodiesterase activities confirms that the presence of a mu-hydroxo bridge during phosphotriester hydrolysis is correlated with a lower pK(a) for the nucleophile, consistent with a general base function during catalysis.
About this Structure
2R1M is a Single protein structure of sequence from Agrobacterium tumefaciens with , , and as ligands. Active as Aryldialkylphosphatase, with EC number 3.1.8.1 Known structural/functional Sites: , , and . Full crystallographic information is available from OCA.
Reference
In crystallo capture of a Michaelis complex and product-binding modes of a bacterial phosphotriesterase., Jackson CJ, Foo JL, Kim HK, Carr PD, Liu JW, Salem G, Ollis DL, J Mol Biol. 2008 Feb 1;375(5):1189-96. Epub 2007 Nov 1. PMID:18082180
Page seeded by OCA on Thu Feb 21 18:43:56 2008
Categories: Agrobacterium tumefaciens | Aryldialkylphosphatase | Single protein | Carr, P D. | Foo, J L. | Jackson, C J. | Kim, H K. | Liu, J W. | Ollis, D L. | Salem, G. | CO | DPF | EDO | FE2 | Hydrolase | Metalloenzyme | Opda | Phosphotriesterase
