*2.1. Production of DgAS Protein in Recombinant Escherichia coli*

The *DgAS* gene was amplified from genomic DNA of *Deinococcus geothermalis*, and subcloned into an expression plasmid *pETDuet-1* fused with six histidine residues in the N-terminal. The constructed *pETDuet-DgAS* plasmid (Figure 1a) was overexpressed in *E. coli*, and induced with 0.2 mM of isopropyl β-D-1-thiogalactopyranoside (IPTG). The soluble DgAS proteins were then successfully purified with Ni2<sup>+</sup> chelate affinity chromatography, as shown in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) (Figure 1b).

**Figure 1.** Production of the DgAS from *Deinococcus geothermalis* in *E. coli*. (**a**) Diagram of the constructed plasmid; (**b**) SDS-PAGE of the produced DgAS in recombinant *E. coli*. M: protein marker; lane 1: total protein without IPTG-induction; lane 2: total protein with IPTG-induction for 20 h; lane 3: purified DgAS.
