FIGURE 4.

In vitro co-affinity purification of the NTD of PilC and the ATPase PilB. A, the purified NTD of PilC was incubated with whole cell lysates of the PAK strain and then repurified by nickel affinity chromatography as described under “Experimental Procedures.” Whole cell lysates, the column flow-through, and imidazole wash fractions (0, 5, and 300 mm) were probed with anti-PilC or anti-PilB antiserum. Full-length PilC present in the lysates did not bind the column. A fraction of PilB was retained in the 300 mm imidazole fraction. B, when the NTD of PilC was not included, PilB did not appear in the 300 mm imidazole elution fraction.