Channeling and conformational changes in the heterotetrameric sarcosine oxidase from Corynebacterium sp. U-96

We characterized the crystal structures of heterotetrameric sarcosine oxidase (SO) from Corynebacterium sp. U-96 complexed with methylthioacetate (MTA), pyrrole 2-carboxylate (PCA) and sulphite, and of sarcosine-reduced SO. SO comprises α-, β-, γ- and δ-subunits; FAD and FMN cofactors; and a large i...

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Bibliographic Details
Published in:Journal of biochemistry (Tokyo) 2010-10, Vol.148 (4), p.491-505
Main Authors: Moriguchi, Tomotaka, Ida, Koh, Hikima, Takaaki, Ueno, Go, Yamamoto, Masaki, Suzuki, Haruo
Format: Article
Language:English
Subjects:
Catalytic Domain
channeling
conformational change
Corynebacterium
Corynebacterium - enzymology
Corynebacterium sp.U-96
crystal structure
Crystallography, X-Ray
heterotetrameric sarcosine oxidase
Leucovorin - chemistry
Leucovorin - metabolism
Models, Molecular
Molecular Structure
Mutagenesis, Site-Directed
Protein Conformation
Protein Subunits - chemistry
Protein Subunits - genetics
Protein Subunits - metabolism
Sarcosine Oxidase - chemistry
Sarcosine Oxidase - genetics
Sarcosine Oxidase - metabolism
Tetrahydrofolates - chemistry
Tetrahydrofolates - metabolism
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Summary:We characterized the crystal structures of heterotetrameric sarcosine oxidase (SO) from Corynebacterium sp. U-96 complexed with methylthioacetate (MTA), pyrrole 2-carboxylate (PCA) and sulphite, and of sarcosine-reduced SO. SO comprises α-, β-, γ- and δ-subunits; FAD and FMN cofactors; and a large internal cavity. MTA and PCA are sandwiched between the re-face of the FAD isoalloxazine ring and the β-subunit C-terminal residues. Reduction of flavin cofactors shifts the β-subunit Ala1 towards the α-subunit Met55, forming a surface cavity at the oxygen-channel vestibule and rendering the β-subunit C-terminal residues mobile. We identified three channels connecting the cavity and the enzyme surface. Two of them exist in the inter-subunit space between α and β-subunits, and the substrate sarcosine seems to enter the active site through either of these channels and reaches the re-side of the FAD isoalloxazine ring by traversing the mobile β-subunit C-terminal residues. The third channel goes through the α-subunit and has a folinic acid-binding site, where the iminium intermediate is converted to Gly and either formaldehyde or, 5,10-methylenetetrahydrofolate. Oxygen molecules are probably located on the surface cavity and diffuse to the FMN isoalloxazine ring; the H₂O₂ formed exits via the oxygen channel.
ISSN:0021-924X
1756-2651
DOI:10.1093/jb/mvq083