Portal:Medicine/Selected picture/43, 2006

Ribbon diagram of a heptameric, 63 kDa cleavage fragment (PA₆₃) of the protective antigen (PA) protein, produced by Bacillus anthracis as part of the anthrax toxin. The quaternary structure is that of a pre-pore, which later forms a channel that allows other toxins into the cytosol of the target cell, so the pathogen can cause damage to the host.

Photo credit: [1]