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

J Biochem. 2010 Oct;148(4):491-505. doi: 10.1093/jb/mvq083. Epub 2010 Jul 30.


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 H(2)O(2) formed exits via the oxygen channel.

MeSH terms

  • Catalytic Domain
  • Corynebacterium / enzymology*
  • Crystallography, X-Ray
  • 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


  • Protein Subunits
  • Tetrahydrofolates
  • Sarcosine Oxidase
  • Leucovorin

Associated data

  • PDB/3AD7
  • PDB/3AD8
  • PDB/3AD9
  • PDB/3ADA