part of MAPK cascade protein serine/threonine kinase activity MAP kinase kinase kinase activity https://github.com/geneontology/go-ontology/issues/30193 MEKK2 EC:2.7.11.25 mitogen-activated protein kinase kinase kinase activity MEKK3 MEKK1 Reactome:R-HSA-727819 cMos Catalysis of the phosphorylation and activation of a MAP kinase kinase; each MAP kinase kinase can be phosphorylated by any of several MAP kinase kinase kinases. GO:0004710 MEKK MAPKKK activity STK28 ATP:protein phosphotransferase (MAPKKKK-activated) activity MAP3K Reactome:R-HSA-933530 Reactome:R-HSA-2730887 MEK kinase activity MetaCyc:2.7.11.25-RXN Reactome:R-HSA-451649 cRaf GO:0004709 MLTK MEKK activity REKS MLK-like mitogen-activated protein triple kinase activity molecular_function Reactome:R-HSA-392530 MAPK/ERK kinase kinase activity Mil/Raf MLTKb MLTKa