FIG. 3.

Overexpression of rPPX from S. solfataricus in E. coli. (a) E. coli strain SC21 [BL21(DE3)/pLysS transformed with pET-21b(+) carrying the c50_004-3 insert] and E. coli strain SC3 [BL21(DE3)/pLysS transformed with pET-21b(+)] were grown for 2 h in the presence (+) or in the absence (−) of 1 mM IPTG. Membrane fractions were analyzed by SDS-PAGE and stained with Coomassie blue. The dot indicates the overexpressed rPPX protein. The arrow indicates the 30-kDa product possibly resulting from the degradation of rPPX (see the text). (b) Western immunoblot analysis of the fractions separated in panel a to detect the presence of His tag-containing polypeptides was done as described in Materials and Methods. MW, molecular weight (in thousands).