o-phospho-threonine true O3-phosphothreonine [T:po] O-phospho-L-threonine Residue modification. OBSOLETE remap to MOD:00047. phosphothreonine (2S,3R)-2-amino-3-phosphonooxybutanoic acid PSI-MI TPO threonine phosphate ester 2-amino-3-hydroxybutanoic acid 3-phosphate MI:0177