Normally needed for pro-sigma E processing during sporulation but can be bypassed in vegetative cells. Activates SpoIIAA by dephosphorylation. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Polar septum.