H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 magnesium or manganese ions per subunit. A number of isoforms are produced. According to EST sequences. The protein kinase domain is predicted to be catalytically inactive. In the N-terminal section; belongs to the PP2C family. In the C-terminal section; belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. Was originally thought to correspond to two different genes At2g20040 and At2g20050. Was originally thought to correspond to two different genes At2g20040 and At2g20050.