Structural Molecular Biology Provides New Understanding of How Anthrax Toxin Infects Host Cells


A new explanation has just been published suggesting how the anthrax toxin is able to overcome the normal defenses of cells and cause infections to become lethal. X-ray crystallography experiments at the Stanford Synchrotron Radiation Laboratory (SSRL) have provided the structure of the complex between a protein component of the toxin called the protective antigen (PA) and a surface recep­tor of human cells known as capillary morpho­genesis protein 2 (CMG2). Seven PA molecules bind in this way to seven neigh­boring CMG2 molecules on the cell surface. This complex binds the rest of the anthrax toxin and forms a pocket within the cell membrane. Finally, a pore from the pocket into the interior of the cell then allows the toxin to inject itself into the cell. Knowledge of this mechanism offers a starting point for designing drugs that could stop anthrax infections at the critical step of entry into cells. The structural study was carried out by scientists at the Burnham Institute in La Jolla, California, and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health in Bethesda, Maryland, and is published in the August 19 issue of Nature, along with a featured commentary on the paper and its significance.