Effect of Txe–His6, Axe–His6 and His6–Axe on cell-free protein synthesis. (a) Western blot with HisProbe–HRP of cell-free protein synthesis reactions with no DNA added (lane 1), pET28a-relB-His6 DNA added (2), pET28a-relB-His6 and pET21a-txe-His6 DNA added (3), and pET28a-relB-His6 and pET21a-axe-His6 DNA added (4). (b) Western blot with HisProbe-HRP of cell-free protein synthesis reactions with no DNA added (lane 1), pRSF1b-His6-lpp DNA added (2), pRSF1b-His6-lpp and pET21a-txe-His6 DNA added (3), and pRSF1b-His6-lpp and pACYCDuet1-His6-axe DNA added (4). M, Marker lane.