MAPK's are fairly simple, rather small signaling proteins
found in the cytoplasm of the cell consisting of seven alpha helices,
seven beta sheets and a single activation loop. Although there are many
different types of MAPK their basic motif does not change much throughout
all the different types. MAPKK's are designed in a similar way to MAPK.
The MAPKK are a group of seven family members that all share the ability
to phosporylate and activate the Thr-Xaa-Tyr motif in the activation
loop of the MAPK. Although these seven family members differ slightly,
they all have the same proline rich N-terminal and conserved kinase
domain (Vitale et all, 2000).