Purification of NTPases of type IV secretion pathways. Lane a, SCS1 (pMS54), no IPTG added; lane b, SCS1(pMS54), cells were induced for 5 h with 1 mM IPTG; lane c, TrbB, fraction V, 5 μg; lane d, SCS1(pWP4760), no IPTG added; lane e, SCS1(pWP4760), cells were induced for 5 h with 1 mM IPTG; lane f, HP0525, fraction IV, 5 μg; lane g, SCS1(pMS55.1), no IPTG added; lane h, SCS1(pMS55.1) cells were induced for 5 h with 1 mM IPTG; lane i, TrwD, fraction V, 5 μg; M, molecular mass standards, masses are given in kDa. Samples were electrophoresed in an SDS–15% polyacrylamide gel. The gel was stained with Serva Blue R.