Protein phosphatase that dephosphorylates EF-Tu. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 manganese ions per subunit. Activity not affected by inhibitors of phosphatases of the PPP family such as okadaic acid and cypermethrin, or by inhibitors of phosphatases of the PTP family such as sodium orthovanadate. The stp-disrupted strain is 4 times less virulent than the wild strain, demonstrating that stp is required for full virulence of L.monocytogenes in BALB/c mice. Belongs to the PP2C family.