Figure S1. Neighbor-joining tree of the peroxiredoxin (Prxs) family. Bootstrap values (1000 replicates) > 50% are shown.


Figure S2. Multiple amino acid sequence alignment of Bombyx mori peroxiredoxin 4 (BmPrx4) with homologous proteins and the tertiary structure of BmPrx4. (A) The alignment of amino acid sequences of the Prx4 gene in B. mori and other insects. Identical residues are shaded black, whereas similar residues are grey. The amino acids conserved in catalytic regions are marked with asterisks. Conserved cysteine-containing motifs are boxed. Two sequence motifs (Regions I and II) essential to decamer formation in 2-Cys Prx are underlined. (B) The locations of conserved amino acids in the catalytic region are shown.


Figure S3. (A) The sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of the heterologous expression for the Bombyx mori peroxiredoxin 4 (BmPrx4) protein. Lane 1, protein marker; lanes 2 and 3, pellet and suspension of sonicated recombinant BmPrx4 protein induced with isopropyl-β-D-thiogalactopyranoside (IPTG), respectively; lanes 4 and 5, pellet and suspension of sonicated recombinant BmPrx4 protein not induced with IPTG, respectively; lanes 6 and 7, pellet and suspension of sonicated proteins from E. coli BL21 transformed with pET28a plasmid induced with IPTG. (B) Lane 1, protein marker; lane 2, proteins from BL21 cells transformed with plasmid containing the BmPrx4 gene; lane 3, proteins from BL21 transformed with the pET28a plasmid; lane 4, BL21 cell proteins; lane 5, the purified protein. (C) The Western blotting analysis of the heterologous expression of BmPrx4. (D) Protection of DNA cleavage by the recombinant BmPrx4 in a metal-catalysed oxidation system. Lane 1, pUC119 plasmid DNA + FeCl3 + dithiothreitol (DTT); lane 2, pUC119 plasmid DNA + FeCl3; lane 3, pUC119 plasmid DNA + DTT; lane 4, pUC119 plasmid DNA only; lanes 5–10, pUC19 plasmid DNA + FeCl3 + DTT + purified BmPrx4 (12.5, 25, 50, 75, 100 and 125 µg/ml, respectively). SF, supercoiled form; NF, nicked form.

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