With the crystallation of LF, it became possible to understand the binding interaction between LF and members of the MAPKK family. The recent discovery showed that the second domain of LF is the binding area. It has been found that once the MAPKK binds to the LF the amino terminal, or "docking surface" is removed. This prevents the MAPKK from being phosporylated, and thus prevents the phosphorylation of MAPK. Although the basic area of cleavage is known, the mechanism is still unknown (Vitale et all, 1999).