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Reassembled Dihydrofolate reductase

From Bacillus anthracis (n1_3JWC.pdb)

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This enzyme has 4 chains, each divided into 2 domains. I have given each domain a letter from A to H as if they were distinct chains. Domains A, B, C, and D are catalytic domains. Domains E, F, G and H are cofactor-binding domains. They are part of the same chains as A, B, C, and D respectively.

As with other enzymes, the catalytic site is enclosed and physically constrained. This enzyme shows no clear barrel structure.

This enzyme is of particular interest because the binding sites, the cofactor and the substrate are all charged. Therefore it is probably not possible for the tetramer to come together unless substrate and cofactor are present to neutralize the charges. Consequently only the monomer has been observed experimentally.

For further information about this protein, see post of 3 February 2011 on nativeproteins.blogspot.com

Or contact the author, Dr Don Vanselow at dvanselow@hotmail.com

Further details of JSmol available here