Active site heterogeneity in dimethyl sulfoxide reductase from Rhodobacter capsulatus revealed by raman spectroscopy

Bell, A. F., He, X., Ridge, J. P., Hanson, G. R., McEwan, A. G. and Tonge, P. J. (2001) Active site heterogeneity in dimethyl sulfoxide reductase from Rhodobacter capsulatus revealed by raman spectroscopy. Biochemistry, 40 2: 440-448.


Author Bell, A. F.
He, X.
Ridge, J. P.
Hanson, G. R.
McEwan, A. G.
Tonge, P. J.
Title Active site heterogeneity in dimethyl sulfoxide reductase from Rhodobacter capsulatus revealed by raman spectroscopy
Journal name Biochemistry   Check publisher's open access policy
Publication date 2001
Sub-type Article
DOI 10.1021/bi002065k
Volume number 40
Issue number 2
ISSN 0006-2960
Start page 440
End page 448
Total pages 9
Place of publication Washington
Publisher American Chemical Society
Collection year 2001
Language eng
Subject C1
270300 Microbiology
780105 Biological sciences
Abstract Raman spectroscopy has been used to investigate the structure of the molybdenum cofactor in DMSO reductase from Rhodobacter capsulatus. Three oxidized forms of the enzyme, designated 'redox cycled', 'as prepared', and DMSORmodD, have been studied using 752 nm laser excitation. In addition, two reduced forms of DMSO reductase, prepared either anaerobically using DMS or using dithionite, have been characterized. The 'redox cycled' form has a single band in the Mo=O stretching region at 865 cm(-1) consistent with other studies. This oxo ligand is found to be exchangeable directly with (DMSO)-O-18 or by redox cycling. Furthermore, deuteration experiments demonstrate that the oxo ligand in the oxidized enzyme has some hydroxo character, which is ascribed to a hydrogen bonding interaction with Trp 116. There is also evidence from the labeling studies for a modified dithiolene sulfur atom, which could be present as a sulfoxide. In addition to the 865 cm(-1) band, an extra band at 818 cm(-1) is observed in the Mo=O stretching region of the 'as prepared' enzyme which is not present in the 'redox cycled' enzyme. Based on the spectra of unlabeled and labeled DMS reduced enzyme, the band at 818 cm(-1) is assigned to the S=O stretch of a coordinated DMSO molecule. The DMSORmodD form, identified by its characteristic Raman spectrum, is also present in the 'as prepared' enzyme preparation but not after redox cycling. The complex mixture of forms identified in the 'as prepared' enzyme reveals a substantial degree of active site heterogeneity in DMSO reductase.
Keyword Biochemistry & Molecular Biology
Ray-absorption Spectroscopy
Resonance Raman
Crystal-structure
Dmso Reductase
Dimethylsulfoxide Reductase
Catalytic Mechanism
Molybdenum-cofactor
Resolution
Enzyme
Sphaeroides
Q-Index Code C1

Document type: Journal Article
Sub-type: Article
Collection: Centre for Advanced Imaging Publications
 
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