FIGURE 2.

The IFT A complex is stable to increased ionic strength. The membrane plus matrix proteins were extracted from the flagella isolated from 16 liters of fla2 cells and fractionated through a 13-ml 10–25% sucrose density gradient (SW41Ti) in HMDEK buffer containing 300 mm NaCl. A, fractions 7–21 (21.5–13% sucrose) were resolved on a 7.5–15% acrylamide SDS-PAGE gel and stained with Coomassie Blue; the protein streaking visible in the upper half of the gel was due to the high salt present in the gradient fractions. The asterisks (*) denote the higher molecular mass IFT A subunits found at ∼16 S. Sucrose concentrations are shown at the top, whereas the positions of protein mass standards are indicated on the left. B, immunoblot analysis of fractions 7–21. Antibodies to specific IFT subunits are labeled on the left. All six of the IFT A subunits co-sediment at ∼16 S under these conditions. The anti-IFT81 (81.1) indicates the ∼11 S location of the IFT complex B core; the 6.5 S peak of IFT172 (172.1) serves as an example of a peripheral B component that dissociates from the B core in the presence of 300 mm NaCl.