STE11 family kinases are mitogen-activated protein kinase kinase kinase. Eight kinases compose this family and act as an essential component of the MAP kinase signal transduction pathway. STE11 family contains some subfamilys. MAP3K1/2/3/5/6 appears to diverged from SC:STE11, SCBCK1, SP:MHK1 and SP:BR2. SC:STE11 plays an important role in mating and filamentation-invasion pathways, BCK1 is responsible for nutrient sensing and growth, MHK1 is involved in cell-wall integrity, BYR2 participate innutrient sensing and pheromone signaling. MAP3K1/2/3/5/6 also act as key molecules in the JNK pathway, inflammation and cell apoptosis (1).

Reference
1. Kinase Pathway Database:STE11 Family

    STE20 was first identified as a putative MAP4K in mating pathway in yeast and its homologs in human constitute a large family in STE group. STE20 can further be classified into two subclasses, PAK and GCK. Structure analysis shows that the kinase domains in PAKs are located at C-terminal while GCKs kinase domains are located in N-terminal. Three mammalian STE20-like kinases have been reported to be able to phosphorylate MAP3Ks, including HPK1, GLK and PAK2. HPK1 predominantly mediate the activation of the stress-activated SAPK/JNK pathway. PAK2 is activated via binding of the Rac1 or Cdc42 and subsequently involved in direct phosphorylation of MAP3K Raf-1. Besides as a upstream activator of MAPK pathway, STE20 are often used in signaling events, including cell apoptosis, morphogenesis and cytoskeletal rearrangement such as cell motility and cell shape changes (1).

Reference
1. Dan, I., Watanabe, N.M. and Kusumi, A. (2001) The Ste20 group kinases as regulators of MAP kinase cascades. Trends Cell Biol, 11, 220-230. PMID: 11316611

    STE7 (MAP2K, MEK) kinases participate in the MAPK signaling cascades, STE7s are activated by STE11 and subsequent mediate the phosphorylation of MAPK kinases. STE7 are typical dual-specificity kinases and can phosphorylate the conserved TxY motif on MAPK. STE7 can further be classified into five subclasses: MEK1, MEK3, MEK4, MEK5 and MEK7 (1).

Reference
1. Wikinome Annotation:   Kinase Family STE7