One of the three protein components of Anthrax toxin, lethal factor (LF) is a highly specific protease that cleaves members of the mitogen-activated protein kinase kinase (MAPKK) family. LF is comprised of four domains. Domain I binds the protective antigen to enter the target cell, domains II, III, and IV create a long groove to hold and cleave the MAPKK proteins. Alternative Names: Bacillus Anthracis Protein, Recombinant B Anthracis , Bacillus Anthracis Lethal Antigen Recombinant Protein, Anthrax Protein