Anthrax lethal factor, molecular model. Lethal factor (LF) is one of the toxins produced by spores of the bacterium Bacillis anthracis. Spores enter the body and release their toxins, including LF which cleaves an enzyme vital for cell signalling. This renders the cells unable to function normally. If inhaled, anthrax is often fatal. The disease most commonly affects cattle, sheep and goats, but can also infect humans. In this model, solid colours represent the secondary structure of the protein (spiral ribbons are alpha helices; arrows are beta sheets), and the faded tubular structure behind represents the individual atoms and bonds.