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A conformational sampling model for radical catalysis in pyridoxal phosphate- and cobalamin-dependent enzymes
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Menon, Binuraj R. K., Fisher, Karl, Rigby, Stephen E. J., Scrutton, Nigel S. and Leys, David (2014) A conformational sampling model for radical catalysis in pyridoxal phosphate- and cobalamin-dependent enzymes. Journal of Biological Chemistry, 289 (49). pp. 34161-34174. doi:10.1074/jbc.M114.590471
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Official URL: http://dx.doi.org/10.1074/jbc.M114.590471
Abstract
Cobalamin-dependent enzymes enhance the rate of C–Co bond cleavage by up to ∼1012-fold to generate cob(II)alamin and a transient adenosyl radical. In the case of the pyridoxal 5′-phosphate (PLP) and cobalamin-dependent enzymes lysine 5,6-aminomutase and ornithine 4,5 aminomutase (OAM), it has been proposed that a large scale domain reorientation of the cobalamin-binding domain is linked to radical catalysis. Here, OAM variants were designed to perturb the interface between the cobalamin-binding domain and the PLP-binding TIM barrel domain. Steady-state and single turnover kinetic studies of these variants, combined with pulsed electron-electron double resonance measurements of spin-labeled OAM were used to provide direct evidence for a dynamic interface between the cobalamin and PLP-binding domains. Our data suggest that following ligand binding-induced cleavage of the Lys629-PLP covalent bond, dynamic motion of the cobalamin-binding domain leads to conformational sampling of the available space. This supports radical catalysis through transient formation of a catalytically competent active state. Crucially, it appears that the formation of the state containing both a substrate/product radical and Co(II) does not restrict cobalamin domain motion. A similar conformational sampling mechanism has been proposed to support rapid electron transfer in a number of dynamic redox systems.
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) | ||||
| Journal or Publication Title: | Journal of Biological Chemistry | ||||
| Publisher: | American Society for Biochemistry and Molecular Biology | ||||
| ISSN: | 0021-9258 | ||||
| Official Date: | 2014 | ||||
| Dates: |
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| Volume: | 289 | ||||
| Number: | 49 | ||||
| Page Range: | pp. 34161-34174 | ||||
| DOI: | 10.1074/jbc.M114.590471 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access |
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