Bacillus anthracis, with (inset) a depiction of the findings of Drum et al.1. Anthrax oedema factor (EF) before (left) and after (right) binding to calmodulin, shown in red. The yellow and blue arms of EF grab and twist calmodulin so that it can no longer send signals to other proteins in the host cell. At the same time, binding of calmodulin organizes two loops (orange and purple), creating a binding site for ATP that allows catalytic conversion to cyclic AMP to proceed.

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