3D Structure of DNA Methyltransferase

See double-stranded DNA.

3D Structure of DNA Methyltransferfase

CPK Color Scheme


You are looking at the 3D structure of DNA methyltransferase (MT; purple) isolated from Haemophilus haemolyticus. This enzyme takes a methyl group from the donor molecule and cofactor 5-adenosyl-L-methoinine (AdoMet; shown as ball and stick with CPK colors). The MT is composed of 327 amino acids which is smaller than most MT.

Reset the structure or view the protein with alpha helices in dark pink and beta strands golden colored.

First, look at the consensus sequence in the target DNA:
5' G (pink), C (yellow), G (orange) and C (green) 3'.
Notice the cytosine that will be methylated is flipped away from the central portion of the DNA double helix. Hydrogen bonds are shown as dotted lines.

Now look at the donor molecule, AdoMet, shown as ball and stick in CPK colors. Notice how an adenine and a methionine are fused together. The sulfur group in the methonine appears more orange than is typical.

Let's bring the MT back and look at its binding site. The catalytic cysteine (amino acid 81) is shown in spacefill view with CPK colors.

Cysteine 81 attacks carbon number 6 on the cytosine which permits the methyl group from AdoMet to form a new covalent bond with carbon number 5 on the cytosine.

In our final view, let's look at the binding pocket for AdoMet. This structure, and many of the amino acids that form it, is highly conserved in many MT's. Creating the surface view takes a little time....

Use this button to slab through the protein and see AdoMet resting in the binding site.

If you want to get rid of the surface layer, you will have to reload this web page.