Figure 4.
(a) The HMP-P synthase homodimer. The protomer consists of
three domains. The N-terminal domains are colored in shades of
blue, the ( )[8]
core domains are colored in shades of green and the C-terminal
domains are colored in shades of red. HMP-P is shown as a
ball-and-stick model. The final 66 amino acids are disordered;
however, the final ordered residues, which immediately precede a
conserved CX[2]CX[4]C motif, extend into the active site of the
adjacent protomer. The C-terminal tail is anchored to the
adjacent protomer by a three-helix bundle motif located at the
beginning of the C-terminal domain. (b) Stereoview of the HMP-P
synthase active site with modeled SAM and the [4Fe-4S] cluster.
The atoms are color coded by atom type (green = C, blue = N, red
= O, yellow = S and orange = Fe). The substrate analog IMR 22
from the crystal structure is shown. Residues Cys561, Cys564 and
Cys569, SAM and the [4Fe-4S] cluster were modeled using biotin
synthase as a guide. Hydrogen bonds are indicated by dotted
lines. (c) Superposition of the ( )[8]
domains from HMP-P synthase and biotin synthase (PDB ID 1R3O).
HMP-P synthase is shown in blue, and biotin synthase is shown in
silver. The [4Fe-4S] cluster and SAM from biotin synthase are
shown as ball-and-stick models.
)[8]
core domains are colored in shades of green and the C-terminal
domains are colored in shades of red. HMP-P is shown as a
ball-and-stick model. The final 66 amino acids are disordered;
however, the final ordered residues, which immediately precede a
conserved CX[2]CX[4]C motif, extend into the active site of the
adjacent protomer. The C-terminal tail is anchored to the
adjacent protomer by a three-helix bundle motif located at the
beginning of the C-terminal domain. (b) Stereoview of the HMP-P
synthase active site with modeled SAM and the [4Fe-4S] cluster.
The atoms are color coded by atom type (green = C, blue = N, red
= O, yellow = S and orange = Fe). The substrate analog IMR 22
from the crystal structure is shown. Residues Cys561, Cys564 and
Cys569, SAM and the [4Fe-4S] cluster were modeled using biotin
synthase as a guide. Hydrogen bonds are indicated by dotted
lines. (c) Superposition of the (