STE7

STE7 subfamily members are the dual-specificity MAP2K tier of the STE group, exemplified by MEK1 and MEK2, which phosphorylate ERK1/2, and by MKK4, MKK3, MKK6, and MKK7, which activate JNK and p38 kinases. Named for yeast Ste7, these enzymes carry a kinase domain flanked by proline-rich docking motifs and use a conserved activation loop that upstream MAP3Ks phosphorylate on serine and threonine residues. Their strict dual specificity and narrow substrate choice make them signal-fidelity checkpoints in proliferation and stress responses, and MEK inhibitors are approved cancer drugs. Recombinant STE7 kinases support cascade and inhibitor studies.