Crystal structure of uroporphyrinogen III synthase from Pseudomonas syringae pv. tomato DC3000

► The structure of psU3S was determined by the SAD method at 2.5 Å resolution. ► The conformation of the psU3S structure is different from that of other homologous U3S structures previously reported. ► Mutations of conserved residues Arg219 and Arg164 in psU3S caused reduced enzymatic activity. ► We proposed a possible catalytic mechanism of U3S based on structural and mutation information.