FIG. 4.

Both SepF and Ftn6 interact with FtsZ, and SepF but not Ftn6 stimulates assembly and/or stability of FtsZ polymers. Phase-contrast images and corresponding fluorescence images showing that GFP-SepF (A) and GFP-Ftn6 (A′) decorate the FtsZ polymer network are presented. Effects of SepF (B and C) and Ftn6 (B′ and C′) on the sedimentable polymeric mass of FtsZ are shown. FtsZ (4.5 μM) was polymerized in the absence or presence of different concentrations of SepF or Ftn6, and the polymers were collected by centrifugation. The protein content in the pellets were visualized by Western blotting using anti-His tag antibodies (B and B′) and then quantified (C and C′) as described in Materials and Methods. Lanes T represent the total amount of FtsZ used for the experiment, which was performed twice. Results show data representing the polymeric mass obtained when FtsZ was incubated without GTP (lanes 1) or with 1 mM GTP (lanes 2 to 5) in the absence (lanes 2) or in the presence of 2 μM (lanes 3), 3 μM (lanes 4), and 4 μM (lanes 5) concentrations of either SepF (B and C) or Ftn6 (B′ and C′).