Molecule of the Month: Anthrax Toxin
Anthrax bacteria build a deadly three-part toxin
A Lethal Combination
Keeping Deadly Company
Lethal Factor and Edema Factor
Lethal factor (shown on the right) attacks at another sensitive spot. It is a very specific protease that makes a cut in several similar mitogen-activated protein kinase kinases. In the illustration, a small segment of this target is shown in green, bound in the active site of the toxin. These kinases are essential steps at the end of another signalling pathway which is important in cell growth and proliferation. The lethal factor destroys this control by disabling one key step in the chain of messsages.
Exploring the Structure
Activation of Edema Factor
The edema factor is activated once it gets inside cells by binding to calmodulin, a protein that is very common in our cells. The factor is shown before activation on the left in PDB entry 1k8t and after activation on the right in PDB entry 1k90. Notice how calmodulin, shown in yellow, opens up the edema factor, making the active site more available. It also shifts the placement of two key loops, shown in magenta. In the unactivated form, one of these loops hangs down away from the active site and the other is disordered, as indicated by the magenta dots. In the activated form, these two loops hold ATP tightly, forming part of the active site that will convert it to cyclic AMP. Click the JSmol tab to explore these two structures in an interactive view.
April 2002, David Goodsellhttp://doi.org/10.2210/rcsb_pdb/mom_2002_4