Cytosolic LATS1 and LATS2 are phosphorylated by phospho-STK4 (p-MST1). LATS proteins are known to form complexes with MOB1 proteins and this reaction is annotated with LATS:MOB1 complexes as its substrate. Likewise, phosphorylated (active) STK4 (p-MST1) and SAV1 are known to form a complex and that complex is annotated as the catalyst of this reaction. Serine-909 and threonine-1097 have been identified as LATS1 residues phosphorylated by STK4 (MST1) kinase. The target residues of LATS2 have not been identified experimentally but are inferred to be serine-871 and threonine-1041 based on sequence similarity (Chan et al. 2005).