Figure 1: Two missense point mutations, D949V (SNP A2846T) and C953S (SNP G2858C), and one exon 14 deletion (SNP In14 1G>A) change or delete core sites in the secondary structure of the human DPD domains responsible for 5-FU metabolism. Exon 14 skipping caused a deletion of 55 amino acids (D581-N635). The secondary structure prediction programs, YASPIN, PSIPRED and Jpred 3, were used to predict the secondary structures of human DPD domains and their subsequent changes due to SNPs-derived missense point mutations. The secondary structure elements taken from the pig DPD crystallographic analysis are shown for comparison. NADPH-binding domain III sequence is not shown as it contains a synonymous SNP (Table 1). Some of the domain sequences not involved in SNPs or functions are omitted due to the space limitation. Conserved residues between human and pig are shaded in light grey. The amino acids substituted or deleted in human DPD due to SNP including fifty-five amino acids (D581-N635) corresponding to exon 14 highlight in red. Pig DPD functional sites [9] are highlighted with colors as follows. In domain I, C79, C82, C87 and C140 (yellow) and C91, C130, C136 and Q156 (cyan) coordinate two Fe-S clusters. In domain II, E218, K219, and L26 (light green) directly interact with adenosine moiety of FAD; L226, A198, and D481 (yellow) bind to its diphosphate moiety; R235, T489, and V129 in domain 1 (pink) interact with the isoalloxazine ring of FAD. In domain IV, FMN interacts with three cis-peptide bonds (S587 and P588, W751 and P752, A734 and T735, yellow), K574 and K709 (pink) binding to its isoalloxazine ring, and K574-interacting E611 and L612 (pink). 5-FU interacts with N609, N668, N736, T737 and S670 (light green), indirectly with the side chains of M642, I613, T575, and N668 (light green), with the active site loop (S670-L682) (bold letters) including the catalytically crucial C671 (cyan). In domain V, C953, C956, C959 and C996 (yellow) and C963, C986, C989 and C992 (cyan) coordinate two Fe-S clusters. H: Helix, E: Strand, C: Coil.