Biochemistry I Succinate Dehydrogenase
 

 Highlights:

  Suc-FAD
   + F2S
   + F4S, F3S
   Add MQ7
   F2S cluster
   Res. Disp.

 FAD Binding
(M Chain):

   FAD+Suc
   FAD Packing
   FAD Interact.

  Bkg Color:
  White
  Blue
  Black

Succinate dehydrogenase converts succinate to fumarate as part of the TCA cycle. It is the only membrane bound enzyme in the TCA cycle. This structure (1FUM.pdb) is the E.coli enzyme with bound FAD and an inhibitor (oxaloacetic acid, OAA). The OAA has been converted to succinate in this illustration.

The enzyme complex consists of four separate poly-peptide chains:

  • Chain M (dark blue) contains the bound FAD and substrate binding site.
  • Chain N (Light blue) contains the three iron-sulfur centers.
  • Chains O&P (Green) contain the site for Coenzyme Q.
Suggested viewing:
  1. Overall view: The green subunits are embedded in the membrane, the blue subunits will be in the mitochondrial matrix. The bound FAD is colored cyan.
  2. Electron Transport Path:
    1. Suc-FAD: A close up view of the substrate next to the FAD.
    2. +FeS: Iron-sulfur center closest to the FAD.
    3. +FS4,F3S: Next two iron-sulfur centers.
    4. Add MQ7:Coenzyme Q-lipophillic electron carrier.
    5. FeS cluster: The Fe2S2 Cluster is attached to the enzyme via four Cys residues.
    6. Details of FAD-Protein Interaction
      1. FAD+Suc: Close up view of FAD + substrate with van der Waals surface. Note close contact for electron tranfer.
      2. FAD Backing: The FAD is shown in stick, surrounded by the protein. Note how well the cavity fits the FAD molecule (slab mode would be useful here).
      3. FAD Interaction: Specific hydrogen bonds to the adenine, phosphate, and redox part of the FAD. Note the specificity of binding.

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April 2001