Amino acid sequences and 3D secondary structure of PfUDG. A, Alignments of 9 peptide fragments of PfUDG K1 from LC-MS/MS to complete amino acid sequences of PfUDG 3D7 and K1. Blue box, the different amino acid between PfUDG 3D7 and K1; yellow box, conserved amino acid sequences of active site motif I found in fragment 9; B-left, 3D model of PfUDG K1. Cartoon model shows α-helices, blue, β-sheets, red, coils/loops, green. Thr157 is represented as spheres. N, N terminus and C, C terminus. B-right, Molecular surface represents two motifs of the enzyme active sites and their residues (bonds and sticks).