STE11

The STE11 subfamily gathers MAP3K-level enzymes of the STE group, homologous to yeast Ste11, that sit at the apex of MAPK cascades. Members include the MEKK1-4 kinases, mixed-lineage kinases, TAO kinases, and ZAK, all sharing a C-terminal STE11-type kinase domain with variable N-terminal regulatory regions such as PH, CRIB, leucine-rich repeat, or leucine-zipper modules. They respond to stresses, Rho GTPases, or receptor inputs and phosphorylate MEK/MKK-family kinases to drive JNK, p38, and ERK signaling that governs proliferation, apoptosis, and inflammation. Recombinant STE11 kinases are widely used in cascade reconstitution and inhibitor screening.